Atlas-Dissections-Anat-Core

COREANATOMYILLUSTRATED

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COREANATOMYILLUSTRATEDIan Parkin MB ChB

Professor of Applied Clinical Anatomy, University of Dundee, and Royal College of Surgeons,Edinburgh; formerly Clinical Anatomist, University of Cambridge and Senior Lecturer in Anatomy,University of Birmingham

Bari M Logan MA FMA Hon MBIE MAMAA

Formerly University Prosector, Department of Anatomy, University of Cambridge; Prosector,Department of Anatomy, Royal College of Surgeons of England, London and Anatomical Preparator,Department of Human Morphology, University of Nottingham Medical School

Mark J McCarthy MB ChB PhD FRCS (Eng) FRCS (Edin)Consultant Vascular Surgeon and Honorary Senior Lecturer, Department of Vascular andEndovascular Surgery, Leicester Royal Infirmary

Hodder ArnoldA MEMBER OF THE HODDER HEADLINE GROUP

First published in Great Britain in 2007 byHodder Arnold, an imprint of Hodder Education and a member of the HodderHeadline Group, an Hachette Livre UK Company,338 Euston Road, London NW1 3BH

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© 2007 Ian Parkin, Bari M Logan, Mark J McCarthy

All rights reserved. Apart from any use permitted under UK copyright law, thispublication may only be reproduced, stored or transmitted, in any form, or by anymeans with prior permission in writing of the publishers or in the case ofreprographic production in accordance with the terms of licences issued by theCopyright Licensing Agency. In the United Kingdom such licences are issued by theCopyright licensing Agency: Saffron House, 6–10 Kirby Street, London EC1N 8TS.

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Foreword ixAcknowledgements xPreface xiHow to use this book xiii

Anatomy and Movement

Parts of the body 1

Anatomical planes 1

Movements of the upper limb 2

Movements of the trunk and lower limb 4

Movements: basic terminology 5

PART I The Skeleton

1 Skeleton, bones of upper limb 8

2 Skeleton of pelvis and lower limb, popliteal fossa, foot ligaments 10

PART II The Vertebral Column

3 Individual vertebrae, lateral view of vertebral column, curvatures 14

4 Vertebral column, spinal cord, meninges, emerging nerves 16

PART III Head and Neck

5 Skull bones and base, external view 20

6 Skull bones and base, internal view; pituitary gland 22

7 Intracranial view: meninges, sinuses, cerebral veins 24

8 Brain, cerebral arteries 26

9 Intracranial view: introduction to cranial nerves 28

10 Ear, associated nerves 30

11 Orbital skeleton, eyelids, conjunctiva 32

12 Orbital muscles, nerves 34

13 Nasal cavity, bones, sinuses, conchae and meati 36

14 Nasopharynx, auditory tube, neurovascular supply of nasal cavity

and nasopharynx, maxillary nerve 38

15 Temporomandibular joint and muscles 40

16 Face: skeleton, muscles; scalp 42

Contents

17 Facial neurovascular supply, salivary glands 44

18 Oral cavity, teeth, tongue 46

19 Soft palate, tonsils, pharynx 48

20 Larynx, trachea 50

21 Laryngeal muscles 52

22 Superficial anterolateral neck, muscles, fascia 54

23 Strap muscles, thyroid and parathyroid glands 56

24 Deep anterolateral neck, thoracic inlet, arteries, vagus nerves 58

25 Deep anterolateral neck, veins, nerves 60

PART IV The Thorax

26 Mediastinum, from left 64

27 Mediastinum, from right 66

28 Thorax: thymus, pleural cavities, thoracic skeleton, intercostal muscles 68

29 Diaphragm 70

30 Lungs: lobes, fissures, bronchi, hila, relations 72

31 Heart: in situ and removed 74

32 Heart: chambers 76

33 Heart valves and conducting system 78

34 Heart: superior and external views, major vessels, coronary arteries

and veins 80

35 The breast, and the thoracic wall in respiration 82

PART V The Abdomen

36 Full abdomen, peritoneum, position of organs 86

37 Lower oesophagus and stomach 88

38 Intestine 90

39 The (vermiform) appendix, pancreas, spleen 92

40 Liver: lobes, surrounding peritoneum and spaces 94

41 Gall bladder, biliary tree, porta hepatis 96

42 Kidneys 98

43 Ureter, suprarenal (adrenal) gland 100

44 Posterior abdominal wall muscles, mesentery 102

45 Anterior abdominal wall 104

PART VI The Male and Female Pelvis

46 Pelvic floor, ischio-anal fossa 108

47 Urogenital triangle, external genitalia 110

48 Penis, clitoris 112

49 Testes, seminal vesicles, prostate gland 114

50 Bladder, female urethra, vagina 116

51 Pelvic ureter, male urethra 118

52 Rectum, anal canal 120

53 Ovary, uterine tubes 122

54 Uterus, cervix 124

PART VII The Torso

55 The torso 128

PART VIII The Upper Limb

56 Axilla, upper limb fascia, veins, arteries 132

57 Shoulder (glenohumeral) joint 134

58 Elbow, superior radio-ulnar, inferior radio-ulnar, wrist and

mid-carpal joints 136

59 Upper limb: anterior muscle groups 138

60 Upper limb: posterior muscle groups 140

61 Superficial palm of hand, median nerve 142

62 Deep palm, ulnar nerve, arteries 144

63 Axillary artery, brachial plexus, radial nerve 146

PART IX The Lower Limb

64 Lower limb: fascia, superficial veins, sural nerve, lymph nodes 150

65 Hip joint, prevention of pelvic tilt 152

66 Knee joint 154

67 Tibiofibular, ankle and tarsal joints, arches of foot 156

68 Sole of foot: plantar aponeurosis, muscle layers, neurovascular supply 158

69 Lower limb: anterior muscle groups 160

70 Lower limb: posterior muscle groups 162

71 Buttock musculature, sciatic nerve 164

Appendix to abdomen and pelvis: structures and concepts not visible on illustrations 166Bibliography 172Index 173

To my dear wife, my family and my friends who have supported me unfailingly throughout the ups and downsof this project. Also to my colleagues past and present, anatomical, educational, technical and secretarial with-out whom I would not have learned enough to get past the first page.Ian Parkin

To Angie James, for bringing me back to life, and to my son Robert Logan.Bari Logan

To my dearest wife, Lucy and my wonderful children Madelyne, Joseph and Oscar. I also dedicate this book tothe loving memory of my father, Anthony McCarthy.Mark McCarthy

Dedications

It is incontrovertible that, in recent years, most undergraduate and postgraduate medical curricula in this coun-try and elsewhere have been so designed as to result in a progressive and significant reduction in the time allo-cated to the study of topographical anatomy. In large measure this has been due to the competing demandsexercised by a variety of other disciplines and the consequent need to reassign educational priorities.

Traditional textbooks of anatomy, with their emphasis on topographical details and their relative lack of clin-ically-pertinent information are thus largely inappropriate to present-day undergraduate medical curricula.

The publication of Core Anatomy – Illustrated is therefore a timely and valuable intervention. The bookaddresses the requirements of the new curricula in a most effective manner.

Taking advantage of their vast experience in teaching and examining medical undergraduates and postgrad -uates, the authors have, in my view, struck a very satisfactory and harmonious balance between the amount oftopographical anatomical information on the one hand, and its clinical relevance on the other. In so doing theyhave succeeded in defining the scope of core anatomical knowledge.

The book is well-organized and the layout is exemplary. The text is written in an admirably lucid and concisestyle, making the subject matter readily assimilable. The plentiful illustrations (in particular, the photographsof dissections) are of superlative quality and do much to enhance the book.

Professor Parkin and his colleagues Messrs Logan and McCarthy are to be generously applauded for theirimaginativeness in conceiving of this volume, and for presenting the subject matter in an unambiguous manner.

I believe that the primary readership for whom this book is intended, namely undergraduate medical and den-tal students, postgraduate surgical trainees and students in paramedical fields, will benefit considerably from thisvery readable and useful book.

I wish the book every success.

Professor Vishy Mahadevan MBBS PhD FRCSEd (Hon) FDSRCSEng FRCSBarbers’ Company Reader in Anatomy & Head of Surgical Anatomy

The Royal College of Surgeons of England, London, UK

Foreword

The authors are most grateful to the following:

For continued encouragement to produce this book and allowing the use of facilities, Professor Bill Harris,Department of Anatomy, University of Cambridge, Cambridge, UK.

For photographs, digital expertise and advice, Mr Adrian Newman, Mr Ian Bolton and Mr John Bashford,Anatomy Visua Media Group, Department of Anatomy, University of Cambridge, Cambridge, UK.

Emily Evans at Medical Illustration for her line drawings.

Georgina Bentliff, Heather Smith, Joanna Koster, Clare Weber, Sara Purdy, Jane Tod, Clare Patterson and allthe team at Hodder Arnold Health Sciences for their help and advice during the preparation of this book.

Furthermore, the illustrations, which are vital to this textbook, would not have been possible without theextreme generosity of those members of the public who bequeathed their bodies for medical education andresearch.

Dissection/anatomical preparation credits

The following individuals are to be credited for their skilled work in preparing the anatomical materialillustrated in this book:

Mrs C Bester – 151D, 159BDr N Borley – 61BMs M Lazenby – 71AB, 109D, 111BC, 113CBari M Logan – 15B, 17ABC, 21ABCD, 23ABCDE, 25ABCD, 27ABCD, 29ABC, 31ABCDEF,

33ABCDEF, 35ABCDE, 37ABCDEF, 39ABCDE, 41ABCD, 43AB, 45ABCDEFG,47ABCD, 49ABC, 51ABCD, 53ABC, 55AB, 57ABC, 59A, 61A, 65A, 67A, 69ABC,71C, 73ABCD, 75ACD, 77ABC, 79ABCD, 81ABCDE, 83ABCD, 87AB, 89B,91ABCD, 93ABCD, 95ABC, 97AB, 99ABC, 101B, 105AB, 109BC, 113B, 115AB,117A, 119A, 121A, 123B, 125A, 129AB, 133AC, 135A, 137ABC, 139B, 143AB,145ABC, 147AB, 151A, 153AB, 155A, 157AB, 161A, 163A, 165ABC

Ms L Nearn – 111A, 113A, 151BC, 159C, 161B, 163BCMr M Watson – 159AMs L Whithead – 109A, 133B, 139A, 141AB

Acknowledgements

Since the early 1990s, major changes have taken place in the way human anatomy is taught withineducational institutions throughout the world.

Essentially these changes may be attributed to the fact that much of the new and exciting, ground breakingresearch in topographical anatomy was done two hundred to four hundred years ago. Anatomists have movedaway from dedicated gross anatomical research and teaching roles towards the scientific disciplines of geneticsor cellular, molecular and neuro-biology, and development. This wealth of new knowledge that is equally essen-tial to the effective practice of any health professional, has led to a substantial reduction in course curriculahours dedicated to the learning of anatomy.

In parallel, there has been a long over due re-appraisal of teaching and learning methodology culminating inan unfortunate and widespread abandonment of practical, cadaver dissection classes in favour of the use of pro-sections, but with the exciting inclusion of small-group and problem-solving tutorials, or interactive multime-dia computer-aided learning. Medical and paramedical education must no longer be divided into undergradu-ate and postgraduate sections, but seen as a continuum which builds and reinforces knowledge as it is requiredin practice.

The mainstay of these educational developments has been the notion of ‘core’ courses, usually supplementedby additional, student-selected course components. ‘Core’ is considered to be a course content offering the mostessential, relevant basic knowledge required for safe practice. However, ‘core’ is open to interpretation andopinion, from institution to institution, and between different academics. Consequently, with our combinedexperience of teaching and assessing gross human anatomy, and of providing highly detailed anatomical mate-rial for both practical classes and museum study, we have created this book of what we consider to be ‘coreanatomy’: the relevant, basic but essential, anatomy required for safe, effective clinical practice, whether as astudent or as a junior, postgraduate trainee.

The book intends to be brief, concise and very much to the point. Although the text contains only theanatomy that is felt to be functionally or clinically important, it is at sufficient depth to facilitate understandingand, therefore, deeper learning. Its concentration may be overwhelming to the first-time reader, but its aim isto review anatomy in preparation for all aspects of clinical work. The content has been designed to fit with, andrelate to the spread of illustrations opposite. Therefore it follows a tight regional and ‘visible’ pattern that mayappear at odds with a more systemic or systematic approach.

We hope the book will be well used and enjoyed. It is not ‘set in stone’, we expect the debate on ‘core’ tocontinue and look forward to comments from our anatomy colleagues on what we should have left out, andwhat we should have included. We will listen to, and take heed of these, but hope that our efforts overall areseen to be contributing a positive move towards supporting and continuing the teaching of human grossanatomy.

Ian Parkin, Bari Logan and Mark McCarthy2007

Preface


The most effective method of learning any subject is to see its relevance, to work with it and to apply it. Thisbook invites the reader to work with the anatomy, cross-referencing between the text page and the accompa-nying illustrations, or vice-versa. Each section should be seen and used as a whole entity.

Throughout the book the anatomical illustrations are shown on the right-hand page of each double-pagespread, with an explanatory key beneath. Numbering in the key is coloured according to the importance of eachanatomical structure. Core anatomical structures are shown with a coloured number, and the first reference tothem in the text is also highlighted in colour. When a number is given in black in the key, this indicates a non-core anatomical structure; these are illustrated in order to provide the reader with more detailed reference ororientation points. Underneath this key is a list showing which illustration(s) each number appears on. Clinicalinformation is highlighted in the text by a sans serif font with a pointing-hand icon in the margin as a simplebut effective method to draw the reader’s eye.

Where possible groups of muscles have been combined functionally and the nerve supply to the whole groupis given at the end of the appropriate paragraph or section. The root value of the major or clinically importantnerves appears in parentheses after the nerve. For example, this sentence follows the paragraph on quadriceps:‘The femoral nerve (L2,3,4) supplies all these muscles (knee jerk L3,4).’ Where such grouping is not possible,the nerve supply (and root value if considered relevant) follows each muscle.

When referring to vertebral levels or to the spinal nerves that contribute to peripheral nerves (i.e. the rootvalue), the accepted abbreviations have been used: cervical (C); thoracic (T); lumbar (L); sacral (S). Therefore,although ‘C6’ can refer to the sixth cervical vertebra or to the sixth cervical spinal nerve the context will makethe choice completely obvious. Cranial nerves are indicated by the usual practice of Roman numerals.

Orientation symbols have been placed in a corner of each illustration, indicating Superior (S), Inferior (I),Right (R), Left (L), Posterior (P), Anterior (A), Medial (M), Lateral (Lat), Dorsal (Dor), Plantar (Plan), Distal(D), Proximal (Prox) and Palmar (Pal).

Terminology

Terminology normally conforms to the International Anatomical Terminology – Terminologia Anatomica –created in 1998 by the Federative Committee on Anatomical Terminology (FCAT) and approved by the 56member Associations of the International Federation of Associations of Anatomists (IFAA). However, the textis for medical students and junior doctors who will be working alongside clinicians who may, themselves, beusing a more familiar terminology. Therefore, such terminology has been included, and where it is shorter andeasier to read it has become the primary one. The textboxes include both terminologies. Similarly, eponymousterminology has been included if in common use.

For example: The Greek adjective ‘peroneal’ is now replaced by the Latin ‘fibular’ for various muscles, vessels,nerves and structures of the lower limb, e.g. fibularis tertius instead of peroneus tertius; fibular artery instead ofperoneal artery; common fibular nerve instead of common peroneal nerve. In this book, the term peroneal isincluded in parentheses to help identify changes for those referring to other older texts, e.g. common fibular(peroneal) nerve. Also note that flexor accessorius is known as quadratus plantae. The adrenal gland is referredto as suprarenal, but the shorter term vas or vas deferens has been retained instead of ductus deferens.

How to use this book


1Anatomy and Movement

Parts of the body

Anatomical planes

Thorax

Head

AbdomenPelvis

Perineum

Thigh

Leg

Plantar surface(sole)

Dorsal surface(dorsum)

Dorsal surface(dorsum)

Hand

Radial sideUlnar side

Forearm

Arm

Neck

Palmar surface(palm)

Foot

Anterior

Mediansagittalplane

Medial

Lateral

Posterior

Superior

Inferior

Coronalplane

Figures reproduced from McMinn RMH, Gaddum-Rosse P, Hutchings RT, Logan BM (1995) McMinn’s Functional and Clinical Anatomy.London: Mosby-Wolfe.

Movements of the upper limb

2 Anatomy and Movement

Shoulderlateral

rotation

Shouldermedialrotation

Shoulderabduction

Shoulderadduction

Elbowextension

Elbowflexion

Shoulderextension

Shoulderflexion


Movements of the upper limb 3

Wrist adduction(ulnar deviation)

Wrist abduction(radial deviation)

Forearmpronation

Fingerextension

Fingerflexion

Wristextension

Wristflexion

Fingersadductionabduction

Forearmsupination


Movements of the trunk and lower limb

4 Anatomy and Movement

Hipextension

Hipflexion

Knee extension

Knee flexion

Hipabduction

Hipadduction

Hiplateral rotation

Hipmedial rotation

Trunklateral flexion


Movements: basic terminology 5

Footinversion

Footeversion

Ankle flexion(plantarflexion)

Ankle extension(dorsiflexion)

Toe extension(dorsiflexion)

Toe flexion(plantarflexion)

Movements: basic terminology

Abduction – movement away from the midline of the bodyAdduction – movement toward the midline of the body

Eversion – turning outwardInversion – turning inward

Flexion – bendingExtension – extending or stretching, straightening out

Pronation – twisting or turning of bones over one anotherSupination – untwisting bones over one another

[terms specific to the forearm bones, radius and ulna]

Rotation – twisting in the long axis of a bone



The Skeleton

Part I

1 Skeleton, bones of upper limb 82 Skeleton of pelvis and lower limb, popliteal

fossa, foot ligaments 10

Skeleton, bones of upper limb

Bones

Bones are essentially for movement, being a system ofsupportive levers connected by joints that usually have acartilaginous component. Bones may be protective, butfracture may cause soft tissue damage. Bone is a mineralstore (calcium, phosphate) and is for haemopoiesis (allbones in infants, but only flat bones in adults).Therefore, they must be dynamic and ever changing,remodelling to fulfil these functions and cope withaltered stresses or loads. For similar reasons bones must bevascular, and fracture may cause considerable blood loss.The high demands and high turnover make bones suscep-tible to poor nutrition. Bones have the general structure ofa compact outer ‘case’, supported by a series of internaltie-bars of cancellous bone. They are covered by perios-teum, with outer fibrous and inner cellular layers.

Cartilage

Cartilage is largely avascular and is tough, flexible andlight. Perichondrium covers cartilage as periosteumcovers bone. Cartilage is typified by cells lying in lacu-nae within a connective tissue matrix. There are threetypes of cartilage. Hyaline cartilage has a smooth,glassy appearance. It forms the costal cartilages (1)and epiphyseal growth plates, and lines synovial jointsas friction-free, articular cartilage (no perichondriumon the joint surfaces). Bones joined to bones by shortpieces of hyaline cartilage are synchondroses or pri-mary cartilaginous joints, e.g. first rib (2) to manubri-um. Fibrocartilage has cells in a fibrous matrix. It isshock absorptive and resilient, to withstand shearing.Joints that contain fibrocartilage are symphyses or sec-ondary cartilaginous joints, e.g. joints in the midline ofthe body, manubriosternal joint (3), vertebral discs(4) and pubic symphysis (5). Elastic cartilage has cellsin a matrix of elastic fibres. It is springy and returns toits original position after displacement.

Axial skeleton

The axial skeleton consists of: skull (6); mandible (7);sternum (8); ribs (9); and vertebrae (10).

Appendicular skeleton

The appendicular skeleton consists of: pelvic girdle

(hip bones (11) and sacrum (12)); pectoral girdle –scapula (13) and clavicle (14); humerus (15), radius(16), ulna (17); femur (18), tibia (19), fibula (20);carpus (21) and metacarpals (22); tarsus (23) andmetatarsals (24); and phalanges (25).

Upper limb bones

The clavicle has a blunt, quadrangular medial end,which forms the sternoclavicular joint (26), the mainligament of which runs from the clavicle to the firstcostal cartilage – the costoclavicular ligament. It is thetrue attachment of the upper limb and pectoral girdleto the rest of the body. As it lies just lateral to the jointit acts as a pivotal point, and thus the movements ofthe sternoclavicular joint may be regarded as of a balland socket joint.

The lateral end of the clavicle forms the acromio-clavicular joint (27) with the acromion (28) of thescapula. The joint is stabilized by the strong coraco-clavicular ligament, which has two segments (conoidand trapezoid) and firmly binds the clavicle to theunderlying coracoid process (29). Both sternoclavicu-lar and acromioclavicular joints are synovial but atyp-ical – they have fibrocartilage on the articular surfacesand also have intracapsular discs. If the clavicle is frac-tured following direct trauma or a fall on the extendedlimb it tends to fracture between the lateral third andmedial two-thirds. The weight of the upper limb pulls thelateral segment of the clavicle inferiorly.

The first metacarpal bone (30) has a saddle-shapedproximal end to provide a more freely mobile car-pometacarpal joint, quite different from the others. Itrotates to allow the movement of opposition of theterminal pulp (pad) of the thumb to that of the littlefinger. The thumb has two phalanges whereas theother digits have three. The metacarpophalangealjoints allow abduction and adduction, and flexion andextension. The combination of these four movementsgives circumduction but no rotation. The interpha-langeal joints allow only hinge movement and thushave strong collateral ligaments.

The anatomical ‘snuff box’ lies at the base of thethumb lateral to the tendon of extensor pollicislongus, between it and the tendons of abductor longusand extensor brevis. The radial artery passes across thefloor of the ‘snuff box’, and tenderness here suggestsscaphoid (31) fracture.

8 The Skeleton

A B C D66

4 111212

1010 10

16 16

21

22

25

21

22

25

1717

4241

43

15 15

4444 4444

45

30

3032

3138

40

45

46

18

232425

121111

15 15

23

89

1

9

5

1717

18

1919

192020

232425

16

16

726 14

13

272829

6

71447

323138

35 34 33

3736

33 343537

39

S

R

I

S

RLL

I

Prox

Lat(L)

M

D

Prox

Lat(L)

M

D

1 Costal cartilages (hyaline cartilage)2 First costal cartilage3 Manubriosternal joint and sternal

angle4 Intervertebral disc5 Pubic symphysis6 Skull7 Mandible8 Sternum9 Ribs

10 Vertebrae11 Hip bone

12 Sacrum13 Scapula14 Clavicle15 Humerus16 Radius17 Ulna18 Femur19 Tibia20 Fibula21 Carpal bones22 Metacarpal bones23 Tarsal bones

24 Metatarsal bones25 Phalanges26 Sternoclavicular joint27 Acromioclavicular joint28 Acromion of scapula29 Coracoid process of scapula30 First metacarpal bone31 Scaphoid bone32 Trapezium33 Trapezoid34 Capitate35 Hamate

36 Pisiform37 Triquetral38 Lunate39 Styloid process of radius40 Styloid process of ulna41 Head of radius42 Tuberosity of radius43 Olecranon of ulna44 Epicondyles45 Head of humerus46 Tuberosities of humerus47 Spine of scapula

A Skeleton (from the front)B Skeleton (from behind)C Bones of the upper limb (from the front)D Bones of the upper limb (from behind)

Skeleton, bones of upper limb 9

Location of numbers: 1A; 2A; 3A; 4A; 5A; 6AB; 7A; 8A; 9AB; 10AB; 11AB; 12AB; 13B; 14AB; 15ABCD; 16ABCD; 17ABCD; 18AB; 19AB; 20AB; 21CD;22CD; 23AB; 24AB; 25ABCD; 26A; 27A; 28A; 29A; 30CD; 31CD; 32CD; 33CD; 34CD; 35CD; 36C; 37CD; 38CD; 39C; 40D; 41C; 42C; 43D; 44CD; 45CD;46C; 47B.

Skeleton of pelvis and lowerlimb, popliteal fossa, footligaments

The pelvic girdle is formed by the hip bones (1) artic-ulating with each other and with the sacrum (2).

The sacro-iliac joints (3) are synovial with a fibrouscapsule supported by strong anterior, posterior andintra-articular ligaments. Movement is limited. The lig-aments relax a little during pregnancy, allowing a widerpelvis for delivery, but possibly causing back pain. (alsocaused by arthritis of the joints). The body weight tendsto tilt the upper sacrum down and forward, but thelower sacrum is prevented from consequently swivel-ling up and backward by the sacrotuberous (4) andsacrospinous (5) ligaments. The former passes to theischial tuberosity from the posterior aspects of theilium, sacrum and coccyx, lying external to thesacrospinous ligament that passes to the ischial spinefrom a smaller, sacral origin. The greater sciatic fora-men (6) transmits nerves and vessels from the pelvis tothe buttock. The lesser sciatic foramen (7) is inferiorto the sacrospinous ligament, therefore inferior to thepelvic floor. Nerves and vessels passing through itenter the perineum.

The pubic symphysis (8) is a fibrocartilaginous jointbetween the bodies of the two pubic bones (9). It issupported by ligaments, has little movement and aidsshock absorption during walking.

The pelvic brim, or entry into the true pelvis, isbounded by the pubic symphysis, pubic crest (10),superior pubic ramus with its pectineal line (11), thearcuate line (12) and the sacral promontory (13). Itfaces anteriorly so that the pubic tubercles (14) are inthe same vertical (coronal) plane as the anterior supe-rior iliac spines (15) but in the same horizontal planeas the ischial spines (16). The pelvic outlet is bound-ed by the coccyx (17), ischial tuberosities (18),ischiopubic rami (19) and pubic symphysis. The out-let faces inferiorly and is for the passage of the urethraand anal canal, and vagina in the female.

The female pelvis must be capable of childbirth;therefore, it is lighter, wider and more rounded thanthe male pelvis, which has a more ‘closed’ appearance,particularly at the outlet. To achieve the wider female

pelvis: the subpubic angle between the ischiopubicrami is wider; superior pubic rami are longer than theacetabular diameter; ischial spines do not encroachupon the outlet; and the pelvic brim is wider in thetransverse direction than anteroposteriorly.

Popliteal fossa

The popliteal fossa (20) lies behind the knee jointbetween semitendinosus/semimembranosus andbiceps femoris superiorly and the two heads of gas-trocnemius inferiorly. In the fossa, the sciatic nervedivides into the tibial and common fibular (peroneal)nerves. The superficial femoral artery and vein passthrough the adductor hiatus to become the poplitealvessels within the fossa, with the artery next to thebone and knee joint capsule. The popliteal artery is atrisk in fractures and dislocations of the knee, resulting inintimal tears and possible limb ischaemia. The tibialnerve lies superficial to the popliteal vein as it runsinferiorly to supply the muscles in the posterior com-partments of the leg. The common fibular (peroneal)nerve lies next to the tendon of semitendinosus, pass-es to the neck of the fibula (where the nerve is at risk ofinjury from fibula fractures) and winds around it.

The popliteal artery divides into the anterior tibialartery and the tibioperoneal trunk. The anterior tibialpasses above the interosseous membrane to join thedeep fibular (peroneal) nerve. The tibioperoneal trunkdivides into the posterior tibial artery, which runs withthe nerve of the same name and fibular (peroneal)artery, which supplies the fibular muscles.

Foot ligaments

Many ligaments hold the tarsal and metatarsal bonestogether. The fibrocartilage spring ligament (plantarcalcaneonavicular) supports the head of the talus (40)by passing from the sustentaculum tali (41) to thenavicular (42). The long and short plantar ligamentspass from the calcaneus (43) to the cuboid (44). Theshort ligament attaches proximal to the groove forfibularis (peroneus) longus (45), the long ligamentattaches distally, converting the groove into a canal.On the dorsum of the foot, the bifurcate ligamentsupports the arch from above and passes in two direc-tions, from calcaneus to cuboid and calcaneus tonavicular.

10 The Skeleton

1 Hip bone2 Sacrum3 Sacro-iliac joint4 Sacrotuberous ligament5 Sacrospinous ligament6 Greater sciatic foramen7 Lesser sciatic foramen8 Pubic symphysis9 Body of pubic bone

10 Pubic crest11 Pectineal line12 Arcuate line13 Promontory of sacrum

14 Pubic tubercle15 Anterior superior iliac spine16 Ischial spine17 Coccyx18 Ischial tuberosity19 Ischiopubic ramus20 Position of popliteal fossa21 Femur22 Tibia23 Fibula24 Head of femur25 Fovea for ligament of head of

femur

26 Neck of femur27 Greater trochanter28 Lesser trochanter29 Intertrochanteric crest30 Intertrochanteric line31 Linea aspera32 Gluteal tuberosity33 Patella34 Tuberosity of tibia35 Adductor tubercle of femur36 Head of fibula37 Neck of fibula38 Lateral malleolus of fibula

39 Medial malleolus of tibia40 Talus41 Sustentaculum tali of calcaneus42 Navicular43 Calcaneus44 Cuboid45 Groove for fibularis (peroneus)

longus46 Cuneiforms (lateral, intermediate,

medial)

A Articulated pelvis (from above)B Bones of the lower limb (from the front)C Bones of the lower limb (from behind)

D Bones of the foot, dorsal surface (from above)E Bones of the foot, plantar surface (from below)

Skeleton of pelvis and lower limb 11

AB C

D

E

13

13

24

26 27

3028

2832

2524

262927

21 21

31

33

35 35

34 36 36

2020

37 37

23 2322 22

43

4341

40

4442

46 4646 45

40

42 44

4646

46

393940

43

3838

2

17176

574

1818

11141010

8

9

191915

1216Prox

Lat(L)

M

D

Prox

Lat(L)

M

D

P

LR

A

P (Prox)

Lat(L)

M

A (D)

A (D)

Lat(L)

M

P (Prox)

Location of numbers: 1A; 2A; 3A; 4A; 5A; 6A; 7A; 8A; 9A; 10A; 11A; 12A; 13A; 14A; 15A; 16A; 17A; 18A; 19A; 20C; 21BC; 22BC; 23BC; 24BC; 25C;26BC; 27BC; 28BC; 29C; 30B; 31C; 32C; 33B; 34B; 35BC; 36BC; 37BC; 38BC; 39BC; 40BDE; 41E; 42DE; 43CDE; 44DE; 45E; 46DE.


The VertebralColumn

Part II

3 Individual vertebrae, lateral view of vertebral column, curvatures 14

4 Vertebral column, spinal cord, meninges,emerging nerves 16

Individual vertebrae, lateral viewof vertebral column, curvatures

The vertebral column supports the weight of the bodyas well as containing the spinal cord and emergingspinal nerves. It must be strong but flexible, therefore,it is composed of a series of vertebrae, with limitedmovement available between consecutive vertebrae. Atypical vertebra has a body (1), two pedicles (2) andtwo laminae (3), which fuse at the spinous process(4), and two transverse processes (5). The inferiorand superior (6) articular facets form synovial jointswith equivalent facets on the vertebra above andbelow.

There are seven cervical, twelve thoracic and fivelumbar vertebrae. The sacrum and coccyx are formedby fused vertebrae: five in the sacrum, three or four inthe coccyx. At birth, the vertebral column shows theprimary curvature, concave anteriorly. But as theinfant lifts its head, then stands up to walk, secondarycurvatures, concave posteriorly, develop in the cervi-cal and lumbar regions.

Between two consecutive vertebral bodies is anintervertebral disc (7), which has an annulus of fibro-cartilage enclosing a hygroscopic jelly, the nucleus pul-posus. The discs hold the bodies together and provideshock absorption. Their deformation allows limitedmovement, but the direction of that movement is dic-tated by the shape of the articular facets. The wholevertebral column is also supported by ligaments:● anterior longitudinal – anterior to the bodies and

discs● posterior longitudinal – attached to the posterior

aspects of the discs and edges of the bodies● inter-transverse and inter-spinous – between the

transverse processes and between the spines,respectively

● supraspinous – joining the tips of the spines● elastic ligamenta flava – between the laminae.

The typical cervical vertebra has a relatively smallbut wide vertebral body (8). The edges of the uppersurface are turned upward to form joints with the

down-turned edges of the inferior surface of the verte-bra above. These joints may develop a painful arthritis(cervical spondylitis). The transverse processes haveforamina (9), which transmit the vertebral artery. TheC7 spine is palpable as the vertebra prominens.

The atlas (C1) does not have a body, but has two lat-eral masses (10) linked by a short anterior arch and along posterior arch. The upper facets are concave ovalsfor articulation with the skull, allowing much of theflexion/extension of the head and neck. The inferiorfacets are flat and round. They articulate with the axis(C2) and allow rotation around the odontoid peg(dens) (11), which arises from the axis and lies behindthe anterior arch of the atlas. Further ligaments bindthe atlas and axis to each other as well as to the skull.Fracture of the odontoid peg can result in spinal corddamage and death. Likewise, a ‘hangman’s fracture’ is theresult of hyperextension of the cervical spine which leadsto fracture of the pedicle of C2.

The thoracic vertebrae have bodies that are longeranteroposteriorly, and their spinous processes are longand point downward. The bodies and transverseprocesses show facets for the ribs. The lumbar verte-brae have large, wide, weight-bearing bodies andthick, quadrangular spinous processes.

The vertebral column is held upright by erectorspinae, a thick multilayered column of muscle on eachside, posteriorly. Anteriorly and laterally the abdomi-nal wall muscles are also important for vertebral col-umn support and movement. Erector spinae hasmultiple insertions, and it can extend, rotate and flexlaterally. The multiple ligament and muscle insertions areall sites susceptible to strain, giving rise to immediate localback pain, aggravated by associated muscle spasm. Discsdeteriorate with age and the nucleus may rupture or pro-lapse through the annulus to press onto the spinal cordor, more commonly onto a spinal nerve on its way toemerge from an intervertebral foramen (12).

There are valveless veins within the vertebral bodiesthat allow the metastatic spread of tumour into thebodies themselves, e.g. from prostatic, lung and breastcancers.

14 The Vertebral Column

A Skeleton with bones of the left upper and lower limbremoved (from the left)

B Bones of the vertebral column (from the left)C Lumbar vertebra (from above)

D Cervical vertebra (from above)E Atlas (first cervical vertebra) (from above)F Axis (second cervical vertebra) (from above)

1 Body of lumbar vertebra2 Pedicle of lumbar vertebra3 Lamina of lumbar vertebra4 Spinous process of lumbar

vertebra

5 Transverse process of lumbarvertebra

6 Superior articular facet of lumbarvertebra

7 Position of intervertebral disc

8 Body of cervical vertebra9 Transverse foramen of cervical

vertebra10 Lateral mass of atlas, first cervical

vertebra with superior articular

facet for the occipital condyle ofskull

11 Odontoid peg (dens) of axis, thesecond cervical vertebra

12 Intervertebral foramen

Individual vertebrae, vertebral column 15

F

A B

C D E

77

12

18

910

11

563

4

2

SevenCervical

2ycurvature

TwelveThoracic

FiveLumbar

Sacrum

1ycurvature

2ycurvature

1ycurvature

Coccyx

S

PA

I

P

LR

A

P

LR

A

P

LR

A

P

LR

A

S

PA

I

Location of numbers: 1C; 2C; 3C; 4C; 5C; 6C; 7A; 8D; 9D; 10E; 11F; 12B.

Vertebral column, spinal cord,meninges, emerging nerves

Following removal of the overlying skin, erector spinaemuscles, vertebral laminae and spines, the spinal cordis visible from behind.

The spinal cord (1) commences at the foramenmagnum (2) as a continuation of the medulla (3). Inthe adult it usually ends (4) at the L1/2 disc, but atL2/3 in the infant.

The vertebral canal is lined by dura mater (5), form-ing a dural sac that ends at S2. The sac is lined byarachnoid mater. The spinal cord, closely covered bypia mater, is suspended in cerebrospinal fluid in thesubarachnoid space. A flange of pia on each side sendsfine denticulate ligaments to anchor the cord, via thearachnoid, to the overlying dural sac. These, and thefilum terminale, a fibrous extension of the cord run-ning all the way to the coccyx, prevent excessivemovement of the cord. There is an epidural (poten-tial) space (6) containing fat and a plexus of valvelessveins between the dura and the bone, and ligaments ofthe vertebral canal. This potential space is used in anaes-thesia. Infiltration of local anaesthetic agents results intemporary anaesthesia of the nerves below, thereforeallowing surgical procedures to be undertaken for child-birth to take place. A lumbar puncture to collect a sampleof cerebrospinal fluid (CSF) must be done below L1/2 toavoid cord damage. The usual site is L3/4.

The spinal cord is usually supplied by one anteriorand two posterior arteries (7), which freely anasto-mose with each other and are variably augmented byadditional arteries entering the intervertebral foram-ina. Loss of these, say in the thoracic or lumbar region fol-lowing aortic aneurysm, may cause cord ischaemia.

Dorsal rootlets (8), which are sensory, emerge fromthe cord and combine with the motor, ventral rootlets(9) to form the mixed spinal nerves (10). The mixedspinal nerves, still encased in pia, arachnoid and duramater emerge from each intervertebral foramen,

where a swelling, the dorsal root ganglion (11),formed by clusters of sensory cell bodies, is visible onthe nerve. Emerging nerves are named in relation tothe vertebrae. Cervical (C) spinal nerves C1–7 emergeabove cervical vertebrae C1–7. Then the patternchanges. The C8 nerve emerges inferior to C7vertebra. All nerves then emerge inferior to thevertebra which gives the name, e.g. thoracic (T)1below vertebra T1, lumbar (L)1 below vertebra L1,sacral (S)1 below S1 vertebra and so on.

Spinal cord segments are named after the nerve thatarises from them. As the cord ends at L1/2 the remain-ing lumbar, sacral and coccygeal nerves form a bundleof nerves, the cauda equina (12), as they pass to theintervertebral foramina through which they leave thecanal. Consequently spinal cord segments lie progres-sively higher in the vertebral canal. The segments giv-ing rise to nerves C1–8 lie opposite the C1–7vertebrae. Those giving rise to nerves T1–12 lieopposite vertebrae T1–10, whereas the segmentsgiving rise to the five lumbar, five sacral, and coccygealnerves lie opposite vertebrae T11–12 and L1.

Having emerged from the intervertebral foraminaand the dural sheath, the spinal nerves receive postgan-glionic sympathetic fibres. Each nerve then divides intoa dorsal ramus, to supply skin and muscle segmentallyin the posterior midline, and a ventral ramus. Theseventral rami (13) form the cervical (C1–4), brachial(C5–T1) and lumbosacral (L4–5 S1–4) plexuses as wellas named nerves (e.g. phrenic), and the intercostalnerves. The extra cell bodies and nerves required forupper and lower limb function result in the cervicaland lumbar enlargements of the spinal cord.

The lumbar nerves emerge from the intervertebralforamina in a notch between the pedicle and vertebralbody, above the intervertebral disc (14). Therefore, asmall disc prolapse will pass below its own nerve andimpinge on the nerve emerging from the next foramendown. For example an L3 prolapse will compress the L4nerve. More serious disc prolapses extend laterally andmay compress the nerve of the same name too.

16 The Vertebral Column

1 Spinal cord (spinal medulla)2 Margin of foramen magnum3 Medulla oblongata4 Lower end of spinal cord

5 Dura mater (reflected)6 Epidural space7 Posterior spinal arteries8 Dorsal rootlets of spinal nerve

9 Ventral rootlets of spinal nerve10 Spinal nerve11 Dorsal root ganglion within dural

sheath

12 Cauda equina13 Ventral rami14 Intervertebral disc

A Skull and vertebral column opened, with spinal cord insitu (from behind)

B Brainstem and cervical part of the spinal cord (frombehind)

C Vertebral column, cervical region (from behind)D Pelvis left half in a midline sagittal section (from the

right)

Vertebral column, spinal cord, meninges, emerging nerves 17

A

B C

D

3

12

11

8

2

14

12

135

1

61111

1010892

3

7

4

1

2

S

RL

I

S

AP

I

S

RL

I

S

RL

I

Location of numbers: 1ABC; 2ABC; 3AB; 4A; 5C; 6C; 7B; 8BC; 9C; 10C; 11C; 12AD; 13C; 14D.


Head and Neck

Part III

5 Skull bones and base, external view 20

6 Skull bones and base, internal view; pituitary gland 22

7 Intracranial view: meninges, sinuses, cerebral veins 24

8 Brain, cerebral arteries 269 Intracranial view: introduction

to cranial nerves 2810 Ear, associated nerves 3011 Orbital skeleton, eyelids,

conjunctiva 3212 Orbital muscles, nerves 3413 Nasal cavity, bones, sinuses,

conchae and meati 3614 Nasopharynx, auditory tube,

neurovascular supply of nasal cavity and nasopharynx, maxillary nerve 38

15 Temporomandibular joint andmuscles 40

16 Face: skeleton, muscles; scalp 4217 Facial neurovascular supply,

salivary glands 4418 Oral cavity, teeth, tongue 4619 Soft palate, tonsils, pharynx 4820 Larynx, trachea 5021 Laryngeal muscles 5222 Superficial anterolateral neck,

muscles, fascia 5423 Strap muscles, thyroid and

parathyroid glands 5624 Deep anterolateral neck,

thoracic inlet, arteries, vagus nerves 58

25 Deep anterolateral neck, veins,nerves 60

Skull bones and base, externalview

The skull bones(1–11) house the brain (surrounded bythe meninges and cerebrospinal fluid (CSF)) and theorgans of special sense, hearing (plus balance), smell,sight and taste. The nasal and oral cavities are the com-mencement of the respiratory and gastro-intestinal sys-tems, respectively. The mandible (10) articulates withthe skull at the synovial temporomandibular joints(12) for mouth opening and mastication.

From the lateral aspect, the frontal, parietal, tempo-ral (squamous part) and sphenoid (greater wing) meetat the pterion (Illustration C: ‘H’) in the temporalfossa. The middle meningeal artery has anterior (13)and posterior (14) branches that lie inside the skulland supply the meninges. The anterior branch, deep tothe pterion, is particularly vulnerable to external trauma,and rupture causes extradural haemorrhage, i.e. bleedingat arterial pressure between the dura and the overlyingbone.

On the skull base, the maxillae house the upperteeth and form much of the hard palate. They alsocontribute to the face, nasal cavity and orbit. Thehorizontal plates (15) of the L-shaped palatine bonescomplete the hard palate. The greater and lesser pala-tine nerves emerge from foramina in the postero -lateral corners. The perpendicular plates (16) con-tribute to the lateral walls of the nasal cavity.

The body of the sphenoid (17) forms a central strutfor the skull base, and gives attachment to the vomer(18), which forms the posterior aspect of the nasalseptum. The pterygoid process of the sphenoid dividesinto medial and lateral plates (19). The medial plateforms the most posterior bony part of the lateral wallof the nasal cavity and gives attachment to the fasciaand muscles that form the nasopharynx. The lateralplate gives origin to the pterygoid muscles. The greaterwing of the sphenoid is the roof of the infratemporalfossa and has the foramen ovale (20) and, next to itsspine, the foramen spinosum (21). The cartilaginouspart of the auditory (Eustachian) tube lies in thegroove (22) between the greater wing of sphenoid andthe petrous temporal bone.

The squamous temporal is seen on the skull base asthe mandibular fossa (23) and articular tubercle (24)that form the temporomandibular joint. The tympanicplate is the anterior wall of the external acousticmeatus (25) and the posterior wall of the mandibularfossa. The two bones (squamous and tympanic) fuse atthe squamotympanic fissure, which not only givesattachment to the temporomandibular joint capsule,but also has the chorda tympani emerging from itsmedial end. The styloid process (26) gives origin tomuscles that elevate and retract the tongue andpharynx. The mastoid process (27) along with thesuperior nuchal line is the proximal attachment ofsternocleidomastoid and only develops after the infantlifts the head. The petrous temporal bone (28)houses the middle and inner ear. The stylomastoidforamen (29) transmits the facial nerve.

In life the foramen lacerum (30) is filled with carti-lage and nothing of importance passes into or out ofthe skull through it. The internal carotid artery, sur-rounded by its plexus of sympathetic nerves, passesthrough the petrous temporal bone in the carotidcanal (31), which opens in the skull immediatelyabove the foramen lacerum. The internal jugular veinis formed in the jugular foramen (32), and cranialnerves IX, X and XI emerge from the foramen ante-rior to the vein.

The occipital bone fuses with the body of the sphe-noid anterior to the foramen magnum (33); behindthe foramen it forms the posterior aspect of the cra-nium, which gives attachment to many small but pow-erful muscles that hold the head extended or rotate itat the atlanto-axial joint. The superior nuchal line(34) gives attachment to trapezius and sterno cleido-mastoid.

The foramen magnum transmits the medulla toimmediately become the spinal cord. All threemeninges, the CSF, the spinal roots of the accessorynerve, and the vertebral and spinal arteries passthrough the foramen magnum. The occipital condyles(35) form the atlanto-occipital joint for head flexionand extension. The hypoglossal nerve (XII) passesthrough an anterior canal in the condyle. The largeposterior condylar canal (36) transmits an emissaryvein.

20 Head and Neck

A B

C

D

8

25

37

1

3815

1816

1924

23

3231

28

2930

17

11

35

36

11

33

34

20

2221

27

272637

6

7

9

12

11

10

10

1 2

4 5

3 86

925

12

11

271

2

4 5 73

13 14

S

PA

I

S

PA

IA

LR

P

S

PI

I

D

1 Maxilla2 Zygomatic bone3 Nasal bone4 Lacrimal bone5 Ethmoid bone6 Frontal bone7 Sphenoid bone8 Parietal bone9 Temporal bone

10 Mandible11 Occipital bone

12 Temporomandibular joint13 Position of anterior branch of

middle meningeal artery14 Position of posterior branch of

middle meningeal artery15 Horizontal plate of palatine bone16 Perpendicular plate of palatine

bone17 Body of sphenoid bone18 Vomer

19 Medial and lateral pterygoidplates

20 Foramen ovale21 Foramen spinosum22 Groove for cartilaginous part of

auditory tube23 Mandibular fossa24 Articular eminence (tubercle)25 External acoustic meatus26 Styloid process27 Mastoid process

28 Apex of petrous temporal bone29 Stylomastoid foramen30 Foramen lacerum31 Carotid canal32 Jugular foramen33 Foramen magnum34 Superior nuchal line35 Occipital condyle36 Posterior condylar canal37 Zygomatic arch38 Greater palatine foramen

A Skull with individual bones coloured (from the left)B Skull (from the left)C Skull without mandible (from the left). ‘H’ indicates the

suture line union of the frontal, parietal, temporal andsphenoid bones. Dotted lines (drill holes) follow thecourse of grooves on the internal surface of the cranialcavity for branches of the meningeal arteries. The circleindicates the area known as the pterion through thecentre of which passes the frontal branch of the middlemeningeal artery

D Base of skull, external surface (from below)

Skull bones and base, external view 21

Location of numbers: 1ABD; 2AB; 3AB; 4AB; 5AB; 6AB; 7AB; 8AB; 9AB; 10AB; 11ABD; 12AB; 13C; 14C; 15D; 16D; 17D; 18D; 19D; 20D; 21D; 22D;23D; 24D; 25BC; 26C; 27BCD; 28D; 29D; 30D; 31D; 32D; 33D; 34D; 35D; 36D; 37CD; 38D.

Skull bones and base, internalview; pituitary gland

The skull bones (1–11) are seen opposite. Thebranches of the middle meningeal artery (12,13) arevisible in relation to the dura mater (14). Whendescribing the skull base, it is divided into the anterior(A), middle (B) and posterior (C) cranial fossae.

Anterior cranial fossa

The ethmoid bone (11) forms the upper aspect of thenasal cavity and the medial walls of the orbits, which lieon either side of the nasal cavity. The crista galli (17)gives attachment to the falx cerebri. The foramina inthe cribriform plate (18) transmit the olfactory nerves.The foramen caecum (19) transmits an emissary vein thatmay allow spread of infection from outside the skull toinside, which can result in cerebral abscess formation.

As cranial nerves leave the skull they carry withthem short extensions of the meninges that cover thebrain. Such extensions anchor the olfactory nerves (I)to the cribriform plate. However, the brain and olfac-tory tracts are able to move within the skull.Consequently, head injury may cause tearing of the olfac-tory nerves from the olfactory bulb, with resultant loss ofthe sense of smell (anosmia). Fractures of the cribriformplate may allow cerebrospinal fluid (CSF) to leak into thenose and drip from the nostrils (CSF rhinorrhoea).

The orbital plates (20) of the frontal bone and thelesser wings of the sphenoid (21) form the remainderof the anterior cranial fossa.

Middle cranial fossa

The body (5) and greater wings of the sphenoid (22),with petrous (23) and squamous (6) parts of the tem-poral bone, form this fossa. The body of the sphenoidextends upward as two posterior clinoid processes.The medial ends of the lesser wings form anterior cli-noid processes. The four processes look like a Turkishsaddle (sella turcica).

The pituitary gland (hypophysis cerebri) is about thesize of a pea and lies under the diaphragma sellae inthe pituitary fossa (sella turcica) (24), which places itbetween the cavernous venous sinuses and above thesphenoid air sinuses. The gland has a posterior neuro-hypophysis (25) and an anterior adenohypophysis

(26). The former connects to the hypothalamus viathe infundibulum and secretes antidiuretic hormone(to control water reabsorption in the kidney) and oxy-tocin (to control muscle contraction in the uterus andmammary gland). The adenohypophysis secretesmany trophic hormones to influence such events as:body growth; adrenal cortical function; thyroid func-tion; cyclical ovarian function; spermatogenesis; pig-mentation; and female breast development. A portalcirculation that carries releasing factors from thehypothalamus controls hormone release. Tumours ofthe pituitary gland may be surgically approached via thenasal cavity and sphenoid sinuses.

The optic canal (27) carries the optic nerve (II). Themeninges and CSF pass with the nerve to the posterioraspect of the eyeball. Raised intracranial pressure istransmitted along the optic nerve and causes swelling(papilloedema) of the optic disc where the optic nerveenters the eyeball. Such swelling is visible on the retina byophthalmoscopy.

The superior orbital fissure (28) transmits nervesand vessels to and from the orbit: ophthalmic (V1),oculomotor (III), trochlear (IV) and abducent (VI)nerves and ophthalmic veins. The foramen spinosum(29) transmits the middle meningeal artery, whereasthe foramen ovale (30) transmits the mandibular divi-sion of the trigeminal nerve (V3). The carotid canalopens in the upper aspect of the foramen lacerum(31). Therefore the internal carotid artery lies just tothe side of the body of the sphenoid, above the fora-men lacerum. A small fossa (32) at the apex of thebone is the site of the trigeminal ganglion.

Posterior cranial fossa

The posterior surface of the petrous temporal bone, theoccipital bone, and centrally the clivus (33) (the fusedportion of the sphenoid and occipital bones) form theposterior cranial fossa. The overlying dural venoussinuses may indent and mark the bones (34,35).

The internal acoustic meatus (36) transmits thefacial (VII) and vestibulocochlear (VIII) nerves. Theglossopharyngeal (IX), vagus (X), and accessory (XI)nerves leave the skull through the jugular foramen(37). The foramen magnum (38) transmits the spinalcord, as it becomes the medulla, with its associatedmeninges and blood vessels.

22 Head and Neck

A

B

C

D

E

S

AP

I

S

AP

I

A

RL

P

A

RL

P

S

PA

I

9A

B

C

C

B

A

A

B

C

8

7 6 5

11 10

34

2

1

3436

13

12

17

1340

12

14

39

25

41

26

35

37

23

34

36

19

17

1820

2127

226

24

5

333229

3028

31

38

1615

1 Mandible2 Palatine bone3 Maxilla4 Inferior nasal concha5 Sphenoid bone6 Squamous part of temporal bone7 Occipital bone8 Parietal bone9 Frontal bone

10 Nasal bone11 Ethmoid bone, superior and

middle nasal conchae

12 Position of anterior branch ofmiddle meningeal artery

13 Position of posterior branch ofmiddle meningeal artery

14 Dura mater15 Bone of cranial vault16 Scalp17 Crista galli of ethmoid bone18 Cribriform plate of ethmoid

bone19 Foramen caecum20 Orbital part of frontal bone

21 Lesser wing of sphenoid bone22 Greater wing of sphenoid bone23 Petrous temporal bone24 Pituitary fossa (sella turcica)25 Posterior lobe of pituitary gland

(neurohypophysis)26 Anterior lobe of pituitary gland

(adenohypophysis)27 Optic canal28 Superior orbital fissure29 Foramen spinosum30 Foramen ovale

31 Foramen lacerum32 Trigeminal impression (for

ganglion)33 Clivus34 Position of sigmoid sinus35 Groove for transverse sinus36 Internal acoustic meatus37 Jugular foramen38 Foramen magnum39 Internal occipital protuberance40 Position of pterion41 Pituitary stalk

A Left half of skull in a median sagittal section withindividual bones coloured. Perpendicular plate of theethmoid bone removed to expose the superior andmiddle nasal conchae (from the right)

B Left half of skull in a median sagittal section.Perpendicular plate of the ethmoid bone and mandibleremoved. Grooves for the meningeal arteries are paintedred and sigmoid sinus blue (from the right)

C Dura mater and meningeal vessels (from the left)D Base of skull, internal surface (from above)E Pituitary gland (from above)

Skull bones and base, internal view 23

Location of numbers: 1A; 2A; 3A; 4A; 5AD; 6AD; 7A; 8A; 9A; 10A; 11A; 12BC; 13BC; 14C; 15C; 16C; 17BD; 18D; 19D; 20D; 21D; 22D; 23D; 24D; 25E;26E; 27D; 28D; 29D; 30D; 31D; 32D; 33D; 34BD; 35D; 36BD; 37D; 38D; 39D; 40C; 41E.

Intracranial view: meninges,sinuses, cerebral veins

Meninges

Inside the skull the brain, like the spinal cord, is sur-rounded by the three meninges. The thin, hardly visi-ble membrane of pia mater (1) clothes the brain. Thearachnoid mater (2) covers the brain but does not dipinto the fissures and sulci. It more closely follows thecontours of the overlying dura mater (3) and skull.

Cerebrospinal fluid (CSF) fills the space betweenthe pia and the arachnoid, providing a buoyantwaterbed upon which the brain is cushioned. The CSFis continually synthesized by choroid plexus withinthe ventricles of the brain and flows into the subarach-noid space. The amount of CSF is normally120–150 mL. It is reabsorbed via arachnoid villi thatcluster in granulations (4) that push into the venoussinuses of the dura mater.

Within the skull the dura mater is described as hav-ing a meningeal and a periosteal layer. The two arefused together except at specific sites. The periosteallayer is adherent to the inner surface of the skull andis continuous with the fibrous tissue of the suturesbetween the skull bones. At the foramina, theperiosteal layer of dura is continuous with the perios-teum external to the skull. The meningeal layer sepa-rates from the periosteal layer to leave endothelially-lined dural venous sinuses in the resultant spaces. Themeningeal layer also separates to form two doublefolds of dura mater, the falx cerebri (5) and tentoriumcerebelli (6).

The falx cerebri passes from the crista galli to theinternal occipital protuberance (7). It separates thecerebral hemispheres (8), preventing their shiftingduring rotational movements of the head. Head injurymay force the brain sharply against the firm falx causingcerebral contusion.

The tentorium cerebelli, as the name suggests formsa roof over the cerebellum (9) separating it from theoccipital lobe (10) of the brain. Its attached marginencloses the transverse sinuses (11) and the superiorpetrosal sinuses (12) on the posterosuperior edges of

the petrous temporal bones. Its free margin (13)forms the tentorial notch, through which the brainstem (14) passes. Lesions in the posterior cranial fossaare infratentorial, those above are supratentorial.

Dural venous sinuses

The superior sagittal sinus (15) is in the attached mar-gin of the falx. It usually continues as the right trans-verse sinus. The inferior sagittal sinus, in the free (infe-rior) margin of the falx (16) usually enters the straightsinus (17) in the junction between the falx cerebri andthe tentorium cerebelli. The straight sinus usually con-tinues as the left transverse sinus. The straight, supe-rior sagittal and both transverse sinuses may all join atthe confluence of the sinuses deep to the internaloccipital protuberance. From the protuberance theright and left transverse sinuses pass laterally tobecome the right and left (18) sigmoid sinuses. Theinferior petrosal sinuses lie between the clivus and theapices of the petrous temporal bone. Each sigmoidsinus becomes the internal jugular vein in the jugularforamen, and here the inferior petrosal sinus joins thevein.

A cavernous sinus lies on each side of the body ofthe sphenoid and pituitary gland (19). Each oneextends from the apex of the petrous temporal boneanteriorly toward the superior orbital fissure and fora-men rotundum. The internal carotid artery emergesfrom the carotid canal and bends to pass anteriorlywithin the cavernous sinus. It then curves back uponitself. The series of bends is the carotid siphon that issaid to reduce the pressure of blood flow within theartery. Rarely, an arteriovenous fistula may form betweenthe artery and the sinus.

Cerebral veins drain the deep parts of the brain andconverge on the great cerebral vein that enters thestraight sinus. More superficially, cerebral veins crossthe subarachnoid space to enter the venous sinuses,particularly the superior sagittal sinus.

The brain shrinks slightly with age, causing mild tractionon these cerebral veins. Relatively minor trauma maydamage the veins just as they enter the sinus, causingsubdural venous haemorrhage.

24 Head and Neck

A B

CD

30 29 28 27 32

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1 Cerebral hemisphere covered bypia mater

2 Arachnoid mater3 Dura mater4 Arachnoid granulations5 Falx cerebri6 Tentorium cerebelli7 Internal occipital protuberance8 Cerebral hemisphere9 Cerebellum

10 Occipital lobe (pole)11 Transverse sinus12 Position of superior petrosal

sinus13 Free margin of tentorium

cerebelli14 Brain stem15 Superior sagittal sinus16 Inferior margin of falx cerebri17 Straight sinus

18 Sigmoid sinus19 Pituitary gland20 Frontal lobe (pole)21 Pons22 Medulla oblongata23 Spinal cord (spinal medulla)24 Posterior margin of foramen

magnum25 Anterior margin of foramen

magnum

26 Crista galli of ethmoid bone27 Bone of cranial vault28 Loose connective tissue and

pericranium29 Epicranial aponeurosis (galea

aponeurotica)30 Skin and dense subcutaneous

tissue31 Subarachnoid space32 Lateral ventricle

A Stepped dissection of scalp and cranial vault (fromabove)

B Cranial cavity and brain in a median sagittal section(from the right)

C Brain, cerebral hemispheres (from above)D Cranial cavity in median sagittal section (from the right)

Intracranial view: meninges, sinuses, cerebral veins 25

Location of numbers: 1A; 2AC; 3A; 4C; 5D; 6BD; 7BD; 8BC; 9B; 10BC; 11BD; 12D; 13D; 14B; 15BD; 16D; 17D; 18D; 19BD; 20BC; 21B; 22B; 23B; 24BD;25BD; 26D; 27A; 28A; 29A; 30A; 31A; 32B.

Brain, cerebral arteries

The soft, live brain is supported by the threemeninges, pia, arachnoid (1) and dura mater, as wellas the cerebrospinal fluid (CSF) in the subarachnoidspace. The brain is divided into left and right hemi-spheres. Each has a ventricle (2) that extends from theparietal (3) into the frontal (4), occipital (5) and tem-poral (6) lobes. These lateral ventricles communicatewith the third ventricle (7) that lies between the twohemispheres. The third ventricle leads to the fourthvia the narrow cerebral aqueduct (8). Vascularchoroid plexuses produce CSF, which is exported viaforamina in the fourth ventricle (9) to fill the sub-arachnoid space. In the newborn, obstruction of the nor-mal flow of CSF causes hydrocephaly.

The frontal lobe, anterior to the central sulcus (12),controls the execution and direction of motor function,as well as personality and judgement. Broca’s area (13)controls speech, and the frontal eye field (14) controlseye movement. The parietal lobe is for the reception,recognition and memory of general sensation. The occip-ital lobe, around the calcarine sulcus (15), has thesefunctions for vision. The temporal lobe is associated withhearing and emotion. The two hemispheres communi-cate with each other via the corpus callosum (16).

Motor principles

Nerve fibres or upper motor neurones (UMNs)descend, mainly from the precentral gyrus (17),through the internal capsule to the medulla (18),where they usually cross the midline before impingingon clusters of cells in the anterior horn of the spinalcord. These cells, or lower motor neurones (LMNs)send axons to muscles in the periphery. Cortical con-trol is inverted (upper brain/lower body) as well ascrossed (left hemisphere/right side of body). Uppermotor neurones have excitatory and inhibitory effectson the LMNs. Damage to the UMN classically causesweakness, spasticity, increased reflexes and up-going toes.

Descending cortical fibres also project to the basalganglia and, via the pons (19), to the cerebellum (20).The latter receives ascending, proprioceptive inputfrom the muscles and joints of the body. The basalganglia and cerebellum create circuits to memorize,direct and co-ordinate motor function.

Cranial nerve nuclei in the brain stem usuallyreceive descending cortical fibres bilaterally. But corti-cal supply to the nucleus of the facial nerve is impor-tant. The upper part of the nucleus receives supplyfrom both the left and right cortices, i.e. bilateral sup-ply. The lower part of the nucleus receives supply onlyfrom the opposite cortex. Therefore, a cerebrovascularaccident in one half of the brain will not affect the upperface due to the bilateral supply but will result in weaknesson the opposite side of the lower face.

Sensory principles

The cell bodies of sensory neurones are clustered inganglia lying just outside the central nervous system.The central processes enter the spinal cord, andsynapse with the secondary neurones either immedi-ately (pain and temperature) or in the medulla (dis-criminative touch and proprioception). The secondaryneurones cross the midline and ascend to the thalamusfrom where the tertiary neurones go to the postcentralgyrus (21) of the cortex. Representation is crossed andinverted. Cranial nerves usually project bilaterally. Allsensation reaches the cortex via the thalamus.

Spinal or brain stem reflex arcs link the sensoryinput to the motor output via interneurones.

Arteries

The internal carotid artery (22) emerges from thepetrous temporal bone and bends to pass anteriorlywithin the cavernous sinus. It then curves back uponitself, gives off its first branch, the ophthalmic arteryand divides into the middle (23) and anterior (24)cerebral arteries.

The left and right vertebral arteries (25) fuse toform the basilar artery (26). They supply the spinalcord, the cerebellum and pons. The basilar arterydivides into the posterior cerebral arteries (27).Posterior communicating arteries (28) pass from theposterior cerebrals to the middle cerebrals and theanterior communicating artery (29) links the twoanterior cerebrals. This arrangement creates the anas-tomotic arterial Circle (of Willis) (Illustration D) tosupply the brain. The arteries lie within the CSF.Small aneurysms may form as the arteries bifurcate;these are prone to rupture causing subarachnoid haem-orrhage.

26 Head and Neck

A B

C D

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1 Arachnoid mater2 Lateral ventricle3 Parietal lobe (pole)4 Frontal lobe (pole)5 Occipital lobe (pole)6 Temporal lobe (pole)7 Thalamus lateral to third

ventricle8 Aqueduct of midbrain

9 Fourth ventricle10 Body of fornix11 Interventricular foramen12 Central sulcus13 Broca’s speech area14 Left frontal eye field15 Calcarine sulcus16 Corpus callosum17 Precentral gyrus

18 Medulla oblongata19 Pons20 Cerebellum21 Postcentral gyrus22 Internal carotid artery23 Middle cerebral artery24 Anterior cerebral artery25 Vertebral artery26 Basilar artery

27 Posterior cerebral artery28 Posterior communicating artery29 Anterior communicating artery30 Posterior inferior cerebellar

artery31 Anterior inferior cerebellar artery32 Superior cerebellar artery33 Labyrinthine artery

A Brain, external, veins (from the left)B Brain, external, sulci (from the left)C Brain and brainstem, left half (from the right)D Arterial circle (of Willis) and associated vessels of the

base of brain (from below)

Brain, cerebral arteries 27

Location of numbers: 1A; 2C; 3ABC; 4ABC; 5ABC; 6ABC; 7C; 8C; 9C; 10C; 11C; 12BC; 13B 14B; 15C; 16C; 17BC; 18BC; 19BC; 20ABC; 21BC; 22D;23D; 24D; 25D; 26D; 27D; 28D; 29D; 30D; 31D; 32D; 33D.

Intracranial view: introduction tocranial nerves

Twelve pairs of cranial nerves emerge from the brainor brainstem and exit the skull.

Olfactory nerve (I) is for the sense of smell and arisesfrom the olfactory bulb (1) at the distal end of theolfactory tract (2). Optic nerve (II) (3) is for the senseof sight. The nerves converge at the optic chiasma (4)just above and in front of the pituitary gland (5).Tumours of the gland may extend upward and impingeupon the chiasma to cause bitemporal hemianopia.

Oculomotor nerve (III) (6) supplies all but two ofthe muscles that move the eye, and carries parasympa-thetic fibres to constrict the pupil. It arises from thebrain stem just anterior to the pons (7) and lies on theedge of the tentorium cerebelli (8). Lesions such asabscesses, tumours and haemorrhages may raise theintracranial pressure and force the brain and brain steminferiorly (coning). The oculomotor nerve may be com-pressed and damaged against the edge of the tentorium,with resultant eye signs. In an acute episode, the patientwill be losing consciousness, or be unconscious, and theimportant sign is failure of the pupil to constrict to light.Trochlear nerve (IV) (9) supplies the superior obliquemuscle. It is a thin nerve that emerges from the poste-rior aspect of the brain stem and lies in the free edgeof the tentorium.

Trigeminal nerve (V) (10) passes anteriorly to reachits ganglion (11) in an invagination of dura mater justunder the posterior end of the cavernous sinus. It hasthree divisions, ophthalmic (V1) (12), maxillary (V2)(13) and mandibular (V3) (14). It is the sensory nerveof much of the head, face and orbital, nasal and oralcavities. The ganglion contains the cell bodies of theprimary sensory neurones. The motor root suppliesthe muscles of mastication via V3.

Abducent nerve (VI) (16) arises immediately caudalto the pons and passes upward on the clivus. Theupward course makes it particularly susceptible to anydownward traction on the brain created by raised intracra-nial pressure. There is resultant paralysis of lateral rectus

and the affected eye cannot be abducted. Nerves III, IV,V1 and V2 lie in the lateral wall of the cavernous sinus,and VI lies in the sinus.

Facial nerve (VII) (17) is the motor supply to themuscles of facial expression. It passes through themiddle ear and emerges from the stylomastoid fora-men. The facial nerve carries with it (nervus inter-medius) parasympathetic fibres that leave in thegreater petrosal nerve and the chorda tympani, as wellas fibres for the sensation of taste. The greater petro salis secretomotor to the lacrimal, nasal and palatineglands. Its nerve fibres synapse in the pterygopalatine(hay fever) ganglion. Postganglionic fibres are distrib-uted with branches of V2. The chorda tympani carriestaste from the anterior two-thirds of the tongue and isalso secretomotor to the submandibular and sublin-gual salivary glands. It joins the lingual branch of V3,and its parasympathetic fibres synapse in the sub-mandibular ganglion. Its taste fibres have their cellbodies in the geniculate ganglion, visible as a swellingon the facial nerve in the middle ear.

Vestibulocochlear (VIII) (18) supplies the organsresponsible for hearing and balance. Glossopharyngeal(IX) (19) supplies one muscle (stylopharyngeus) andcarries general sensation and taste from the posteriorone-third of the tongue, the oropharynx and the pala-tine tonsil. It also carries parasympathetic fibres thatrun with its tympanic branch, which supplies sensa-tion to the middle ear.

Vagus (X) (20) supplies the musculature of thepharynx and larynx, and is the parasympathetic nerveto the heart, lungs and much of the intestinal tract.Ganglionic swellings on the vagus house the cell bod-ies of the afferent nerves from the pharynx, larynx,heart, lungs and intestine. Accessory (XI) (21) is actu-ally a spinal nerve arising from C1–5 segments of thespinal cord. It ascends up the spinal canal and throughthe foramen magnum to pass through the jugularforamen to supply sternocleidomastoid and trapezius.Hypoglossal nerve (XII) is a totally motor nerve to thetongue muscles. It is at risk of injury during carotid arterysurgery in the neck.

28 Head and Neck

1 Olfactory bulb2 Olfactory tract3 Optic nerve (II)4 Optic chiasma5 Pituitary gland6 Oculomotor nerve (III)7 Pons8 Free margin of tentorium

cerebelli

9 Trochlear nerve (IV)10 Trigeminal nerve (V)11 Trigeminal ganglion12 Ophthalmic nerve (V1)13 Maxillary nerve (V2)14 Mandibular nerve (V3)15 Foramen rotundum16 Abducent nerve (VI)17 Facial nerve (VII)

18 Vestibulocochlear nerve (VIII)19 Glossopharyngeal nerve (IX)20 Vagus nerve (X)21 Spinal root of accessory nerve

(XI)22 Medulla oblongata23 Vertebral artery24 Basilar artery25 Pituitary stalk

26 Falx cerebri attached to cristagalli of ethmoid bone

27 Middle meningeal artery28 Transverse sinus29 Sigmoid sinus30 Tentorium cerebelli

Intracranial view: introduction to cranial nerves 29

A

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Location of numbers: 1ABC; 2ABC; 3ABC; 4C; 5A; 6ABC; 7C; 8A; 9ABC; 10ABC; 11B; 12B; 13B; 14B; 15B; 16AC; 17ABC; 18ABC; 19B; 20B; 21AB; 22AC;23A; 24AC; 25C; 26AB; 27A; 28A; 29A; 30A.

A Cranial fossae (from above)B Cranial fossae, left cavernous sinus and

trigeminal nerve (from above and left)C Brain and brainstem (from below)

Ear, associated nerves

The ear, for hearing and balance, comprises the auri-cle (pinna), external acoustic meatus (1), tympanicmembrane (2), middle ear and inner ear. Much of theear is housed within the temporal bone and is closelyrelated to the sigmoid venous sinus, middle cranialfossa and internal carotid artery.

The auricle (3–10) (Illustration C), supported byelastic cartilage (Illustration B), gathers sound. Small,rarely used extrinsic muscles (supplied by VII) insertinto the auricle to move it and minimally alter itsshape. The external acoustic meatus has a cartilagi-nous lateral third and a bony medial two-thirds. It is S-shaped and about 2.5 cm long in the adult, but shorterin the infant. The skin is firmly bound to the underly-ing bone and cartilage and therefore, inflammation ispainful. Ceruminous glands (modified sweat glands)secrete wax, which may block the meatus. When usingan auriscope, gently drawing the auricle upward andbackward tends to straighten the meatus.

The tympanic membrane is oval in shape, slopesinferomedially, and bulges inward toward the middleear, the umbo being the point of maximal convexity.There is an upper, flaccid part, but the remainder istense. The malleus attaches to its inner surface.

The middle ear is like a biconcave lens. It is filledwith air and houses the malleus, incus and stapes,which transmit sound waves from the tympanic mem-brane to the cochlea. Tensor tympani (V3) andstapedius (VII) attach to these ossicles to dampenexcessive vibration. The auditory tube (middle ear tonasopharynx) equalizes air pressure on either side ofthe tympanic membrane. Patency of the tube is essen-tial for normal ear function. The epitympanic recess isthe upper aspect of the middle ear and connects viathe mastoid antrum (17) to the mastoid air cells in themastoid process (18). Middle ear infection may spreadto the air cells (mastoiditis).

The inner ear houses the bony labyrinth, itself linedby the fluid-filled membranous labyrinth, and subdi-vided into the cochlea (hearing) and semicircularcanals with utricle and saccule (balance). The stapes

attaches to the oval window of the cochlea to transmitsound waves via the organ of Corti to the cochlearnerve. The semicircular canals are angled to each otherand detect head position for balance, transmitted inthe vestibular nerve.

The internal acoustic meatus (19) transmits VII andVIII with the labyrinthine branch of the basilar artery.Tumours (e.g. acoustic neuromas) may expand into theinternal acoustic meatus and into the angle between thepons and cerebellum to impinge upon these nerves.

Nerves

The auriculotemporal nerve (V3 (20)) is the main sen-sory supply of the auricle, external acoustic meatusand external aspect of the tympanic membrane. Thelatter two are also supplied by the vagus, – thought tocarry a sensory branch of the facial nerve. Herpesaffecting the geniculate ganglion (21) (VII) may affect theexternal meatus (Ramsay–Hunt syndrome) and earexamination may affect heart rate via the vagus. Thegreat auricular and lesser occipital nerves also supplythe auricle.

Middle ear sensation (and that of the internal aspectof the tympanic membrane) is via the tympanicbranch of the glossopharyngeal nerve, which also car-ries parasympathetic (secretomotor) nerves to thetympanic plexus in the middle ear. These leave in thelesser petrosal nerve, which synapses in the otic gan-glion suspended from V3 just below the foramen ovale.Postganglionic fibres pass in the auriculotemporalnerve to the parotid gland.

The facial nerve gives a number of branches as itpasses through the middle ear. It supplies the stapediusmuscle, and proximal injury to the facial nerve will causehyperacusis (pain on loud noises). The chorda tympaniarises from it and passes medial to the tympanic mem-brane. The greater petrosal nerve (26) arises from thegeniculate ganglion and passes to synapse in the ptery-gopalatine ganglion in the pterygopalatine fossa. Thefossa is medial to the pterygomaxillary fissure (27),lateral to the nasal cavity and nasopharynx, posteriorto the orbit and inferior orbital fissure, and superior tothe hard and soft palates. The maxillary nerve V2 (28)enters the fossa via the foramen rotundum.

30 Head and Neck

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1 External acoustic meatus2 Tympanic membrane3 Helix4 Antihelix5 Crus of helix6 Crus of antihelix7 Tragus8 Antitragus9 Lobule

10 Cavum conchae11 Head of mandible12 Styloid process13 Squamous part of temporal

bone14 Tympanic plate of temporal bone15 Zygomatic arch16 Lateral pterygoid plate of

sphenoid bone

17 Mastoid antrum18 Mastoid process19 Facial nerve (VII) and

vestibulocochlear nerve (VIII)within the internal acoustic meatus

20 Mandibular nerve (V3)21 Geniculate ganglion22 Ophthalmic nerve (V1)23 Trigeminal ganglion

24 Trochlear nerve (IV)25 Olfactory tract26 Greater petrosal nerve27 Pterygomaxillary fissure28 Maxillary nerve (V2)29 Coronoid process of mandible30 Ramus of mandible31 Body of mandible

A Skull and mandible (from the left)B Left auricular cartilage (from the left)C Left auricle (from the left)D Cranial fossae, temporal bone dissected to expose the

auditory ossicles (from above and left)E Coronal section through the left ear (from behind)F Skull without mandible (from the left and slightly below)

Ear, associated nerves 31

Location of numbers: 1ACEF; 2E; 3C; 4C; 5C; 6C; 7C; 8C; 9C; 10C; 11A; 12AF; 13A; 14AF; 15AF; 16AF; 17D; 18AF; 19E; 20D; 21D; 22D; 23D; 24D; 25D;26D; 27F; 28D; 29A; 30A; 31A.

Orbital skeleton, eyelids,conjunctiva

The eyeballs are surrounded by muscles and supportedby fat within the orbit. They must maintain their posi-tion and move in absolute synchrony, or double vision(diplopia) will ensue.

Each bony orbit opens on the facial skull, boundedby the frontal bone (1), zygomatic bone (2) andmaxilla (3). The orbit is cone-shaped with the apexpassing backward and medially. This angulation isimportant when considering the actions of the orbitalmuscles.

Orbital skeleton, foramina, fissures and theircontents

● Medial wall – mainly by the lacrimal (4) and eth-moid (5) bones.

● Roof – the orbital part (6) of the frontal and lesserwing of the sphenoid bone (7). The optic foramenor canal (8) is at the apex of the orbit, in the rootsof the lesser wing of the sphenoid. The optic nerveenters the orbit through the optic foramen, with theophthalmic branch of the internal carotid artery.The central artery of the retina arises from the oph-thalmic and passes into the optic nerve to supplyboth it and the retina. Being an end artery, obstruc-tion of the central artery leads to blindness in that eye.

● Lateral wall – greater wing of sphenoid (9) andzygomatic bone. The superior orbital fissure (10) isbetween the roof and lateral wall, i.e. between thelesser and greater wings of the sphenoid.

● Floor – maxilla. The inferior orbital fissure (11) isbetween the lateral wall and the floor, i.e. betweenthe greater wing of the sphenoid and the maxilla.The maxillary (V2) division of the trigeminal nervecontinues through the inferior orbital fissure as theinfra-orbital nerve, which runs in the infra-orbitalgroove (12) in the orbital floor. (The infra-orbitalgroove in some skulls is closed and then named theinfra-orbital canal.) The nerve emerges from theinfra-orbital foramen (13) to supply the skin andconjunctiva of the lower eyelid, cheek and upper lip.

Eyelids and lacrimal mechanism

The skin of the eyelids is thin with no subcutaneousfat. The eyelashes (14) line the edge of each lid to pre-vent dust entering the eye. Like all hairs they havesebaceous glands alongside. These may become infectedand form a ‘sty’. Orbicularis oculi underlies the skin. Ithas an orbital part (15) that encircles the orbit toscrew the eyes tightly shut, and a palpebral part (16)in the eyelids for blinking and keeping the eyelidsopposed to the eyeball. The latter action is essentialfor correct function of the lacrimal mechanism; shouldthe muscle or its nerve supply (VII) be injured the lidmay fall away from the eye. Tears will then run downthe face, possibly leaving the cornea dry and susceptibleto ulceration.

Tarsal plates of fibrous tissue lie deep to orbicularisoculi to give a stiffening support to each lid. Medialand lateral palpebral ligaments connect them to theorbital margins. Meibomian glands lie in the deep sur-face of the tarsal plates. These secrete an oily fluid toprevent evaporation and keep the eye moist. Cysts mayform in the Meibomian glands. The conjunctival mem-brane lines the inner aspect of both lids. It is continu-ous with the skin at the free margins of the lids, butinternally it reflects onto the front of the eyeball tobecome continuous with the corneal epithelium.

The lacrimal gland (Illustrations D, E, F (17)) lies inthe upper, lateral corner of the orbit and secretes intothe conjunctival sac. Blinking of the eyelids sweeps thetears across the eye from lateral to medial to moistenand cleanse the eye. There is a punctum medially ineach lid to collect tears, pass them to the lacrimal sac(18) and then, via the nasolacrimal duct (19), to thenose. Part of orbicularis oculi encircles the lacrimal sacto promote the flow of tears into the lacrimal sac andfrom there into the nasolacrimal duct, obstruction ofwhich causes tears to flow onto the face.

The sensory supply of the cornea, conjunctiva andeyelids is by branches of V1 and V2 (trigeminal nerve).The corneal reflex, blinking when the cornea is touched,is via the nasociliary branch of the ophthalmic (sensory)and facial (motor) nerves.

32 Head and Neck

A B C

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1 Frontal bone2 Zygomatic bone3 Maxilla4 Lacrimal bone5 Ethmoid bone6 Orbital part of frontal bone7 Lesser wing of sphenoid bone8 Optic canal9 Greater wing of sphenoid bone

orbital aspect

10 Superior orbital fissure11 Inferior orbital fissure12 Infra-orbital groove (canal)13 Infra-orbital foramen14 Eyelashes of upper lid15 Orbital part of orbicularis oculi16 Palpebral part of orbicularis oculi17 Lacrimal gland18 Lacrimal sac (upper extremity)19 Nasolacrimal duct

20 Temporal bone21 Nasal bone22 Greater wing of sphenoid bone

(external aspect)23 Palatine bone (orbital part)24 Supra-orbital foramen (notch)25 Medial palpebral ligament26 Supra-orbital artery and nerve27 Upper lacrimal canaliculus28 Lower lacrimal canaliculus

29 Upper lacrimal papilla andpunctum

30 Lower lacrimal papilla andpunctum

31 Mandible32 Orbital fat pad33 Orbital part of lacrimal gland34 Palpebral part of lacrimal gland35 Lacrimal artery and nerve

A Superficial muscles of the eye (from the front left)B Orbit with individual bones coloured (from the front left

and above)C Orbit (from the front and left)D Orbit (from the front left and above)E Nasolacrimal duct (from the front and left)F Left lacrimal gland (from above)

Orbital skeleton, eyelids, conjunctiva 33

Location of numbers: 1BCDE; 2BCDE; 3BCE; 4BC; 5BC; 6B; 7C; 8C; 9C; 10C; 11C; 12C; 13CE; 14AE; 15A; 16A; 17DEF; 18E; 19E; 20BC; 21BCE; 22BC;23BC; 24C; 25A; 26DE; 27E; 28E; 29E; 30E; 31BC; 32E; 33F; 34F; 35F.

Orbital muscles, nerves

There are six muscles for moving the eyeball and onefor elevating the upper lid.

Levator palpebrae superioris (3) arises from theorbital roof and passes to the tarsal plate in the upperlid. It contains smooth and striated muscle, suppliedby the oculomotor nerve (III) (4) and by sympathet-ics. Both are required to hold up the upper eyelid. Ifeither is lost, the lid droops (ptosis).

Four rectus muscles (6–9) arise from a tendinousring encircling the optic foramen and medial end ofthe superior orbital fissure, so many orbital nerves liewithin the cone of these four muscles as they pass for-ward and laterally to insert near the front of the eye-ball. Superior rectus (III) turns the eye upward.Medial rectus (III) turns the eye medially. Inferior rec-tus (III) turns the eye downward. Lateral rectus (VI)turns the eye laterally. As the origin of superior andinferior recti is posteromedial to the eyeball theyimpart a medial pull.

Superior oblique (10) (IV) arises above the tendi-nous ring. It passes forward and through a fibroustrochlea or pulley (11) before turning backward andlaterally to insert on the posterolateral aspect of theeyeball. It turns the eye down and out. Inferioroblique (12) (III) arises from the orbital floor andpasses to the posterolateral aspect of the eyeball. Itturns the eye up and out.

Working in concert the muscles have the followingactions:● Look up – Superior rectus, inferior oblique.● Look down – Inferior rectus, superior oblique.● Look medially – Medial rectus, superior and inferior

rectus.● Look laterally – Lateral rectus, inferior and superior

oblique.The muscles also rotate the eyeball to counteract tilt-ing of the head.

Nerves within the orbit

Branches of the ophthalmic (V1): the lacrimal nerve(13) supplies the upper lateral lid, conjunctiva andadjacent area. It receives parasympathetic fibres forsecretomotor control of the lacrimal gland. The frontal

nerve lies just beneath the roof of the orbit. It dividesinto supra-orbital (15) and supratrochlear (16) nerve,which supply skin and conjunctiva of the upper lid,forehead, and scalp to the vertex. The nasociliarynerve (17), as well as being sensory, carries sympa-thetic fibres from the carotid plexus. These joined theoculomotor nerve in the cavernous sinus. Its eth-moidal branches supply the ethmoidal sinuses (18).The anterior ethmoidal nerve continues into the nasalcavity to supply the anterior aspects of the lateral walland septum, before emerging to supply the skin of thetip of the nose.

The nasociliary nerve ends as the smallinfratrochlear nerve, supplying sensation to skin andconjunctiva at the medial angle of the eye, and theroot of the nose. Sympathetic and sensory fibres leavethe nasociliary in the long ciliary nerves to enter theposterior aspect of the eyeball. The sympathetic fibresare postganglionic, from the superior cervical ganglion,and are for dilatation of the pupil. The sensory fibressupply all the fascial layers of the eyeball including thecornea.

The oculomotor nerve (III) carries parasympatheticfibres that synapse in the ciliary ganglion (19). The post-ganglionic fibres pass in the short ciliary nerves into theeyeball to the constrictor of the pupil and to ciliaris muscle for lens accommodation. Oculomotor nerve injurycauses: pupil dilatation (sympathetic takes over); ptosis(loss of levator palpebrae superioris); and the eye driftsdown and out under the control of lateral rectus andsuperior oblique. There is double vision (diplopia) onlooking medially. Damage to sympathetic fibres (Horner’ssyndrome) also causes ptosis, but with a constricted pupil.The face is flushed and the skin dry on the affected side.

Abducent nerve (VI) (20) injury prevents the eye mov-ing laterally. Trochlear nerve (IV) (21) injury prevents theaction of superior oblique. One would expect difficultylooking down and out. However, lateral rectus and infe-rior rectus perform that function. The test is to ask thepatient to look downward and inward. When the eye isturned medially by medial rectus, inferior rectus cannotact effectively, leaving superior oblique as the only muscleto turn the eye downward. If its action is absent thepatient cannot do so and has difficulty walking downstairsor looking downward to read.

34 Head and Neck

A B C

D E M

P

A

Lat(L)

114

23

22

18 18 15

14

13

9

128

210 617

7

26

22

23

103

1614

2513

2

2021

5

4

9

15

2

244

21

20

15

14

12

36

2

98

3 1516

1127

23

10 18

6 318

2

28

4

13

19

9

14

6

5A

MLat(L)

P

A

MLat(L)

P

S

Lat(L)

M

I

S

PA

I

1 Orbital fat2 Optic nerve (II)3 Levator palpebrae superioris4 Oculomotor nerve (III)5 Trigeminal nerve (V)6 Superior rectus7 Medial rectus8 Inferior rectus

9 Lateral rectus10 Superior oblique11 Trochlea12 Inferior oblique13 Lacrimal nerve14 Lacrimal gland15 Supra-orbital nerve16 Supratrochlear nerve

17 Nasociliary nerve18 Ethmoidal air cells19 Ciliary ganglion20 Abducent nerve (VI)21 Trochlear nerve (IV)22 Cribriform plate of ethmoid

bone23 Crista galli of ethmoid bone

24 Pituitary gland25 Lacrimal artery26 Infra-orbital nerve27 Tendon of superior oblique28 Internal carotid artery

A Orbit with roof removed (from above and behind)B Orbit, superficial dissection (from above and behind)C Orbit with eye removed (from the front)D Orbit, contents with extensive bone removal (from the

left)E Orbit, contents with extensive bone removal (from

above left and behind)

Orbital muscles, nerves 35

Location of numbers: 1A; 2ABCDE; 3BDE; 4ABE; 5AB; 6CDE; 7C; 8CD; 9BCDE; 10BCE; 11E; 12CD; 13BCE; 14ABCDE; 15BCDE; 16BE; 17C; 18ABE; 19E;20AB; 21AB; 22AB; 23ABE; 24A; 25B; 26C; 27E; 28E.

Nasal cavity, bones, sinuses,conchae and meati

The nasal cavity is for the sense of smell, and to filter,warm and humidify inhaled air. The highly vascularmucous membrane is firmly attached to the underly-ing periosteum and contains mucous glands (mucope-riosteum). The overlying epithelium is ciliated, pseu-dostratified columnar with mucus-secreting gobletcells. The cilia and mucus trap and filter particles, themucus humidifies, and the vascularity of the mucosawarms the inspired air. Coarse hairs (1), the first fil-ters, are obvious in the nostrils.

The variable diameter of the passages ensures effi-cient airflow. To withstand the collapsing effect ofinspiratory pressure, the nasal cavity is supported bybone and hyaline cartilages. The nasal bones (2) andnasal cartilages (3, 4) shape the visible nose. Thesmall muscles around the nostrils are for their con -striction and dilatation, to decrease respiratory deadspace, or widen the nostrils for faster air flow.

The midline septum (5) is formed by the vomer (6),the perpendicular plate of the ethmoid (7), and theseptal cartilage (8). A deviated septum may obstructsinus openings, predisposing to sinusitis. Each lateralwall is formed from anterior to posterior by the nasal,maxillary, lacrimal, ethmoid, and palatine bones, andthe medial pterygoid plate of sphenoid. The majorcontributors are maxilla, for the lower half, and eth-moid, for the upper half.

The sphenopalatine foramen, which transmits muchof the neurovascular supply to the nasal cavity, is atthe posterosuperior corner. The medial pterygoidplates give origin to the fascia and muscle of the wallof the nasopharynx, providing continuity between thenasal cavity and the nasopharynx.

The roof is formed from anterior to posterior by thenasal, frontal (9), cribriform plate of ethmoid (10)and sphenoid (11) bones. The floor is formed by themaxilla (12) and horizontal plate of palatine (13).This horizontal, hard palate separates nasal and oralcavities. Nasogastric tubes must be passed horizontallybackward, parallel to the floor of the cavity.

Nasal air sinuses

The frontal, maxilla, ethmoid and sphenoid bones are

hollow. The nasal mucous membrane extends intothese cavities to form the air-filled nasal sinuses. Theirfunction is uncertain, but they may lighten the skull,add resonance to the voice, and insulate the brain.

Mucus secreted in the sinuses must be carried backinto the nasal cavity by the cilia. Should this action beoverwhelmed by a common cold, or the sinus openingsbe obstructed, the mucus may build up and becomeinfected to cause painful sinusitis.

The opening (14) of the maxillary sinus (15) is highup in its medial wall, therefore it is the most difficultto drain, and the one most susceptible to sinusitis. Themaxilla houses the upper teeth and their roots mayextend into the sinus, creating fistulae following extrac-tion.

The ethmoid is excavated by air cells or sinuses (16)that lie between the lateral wall of the nasal cavity andthe medial wall of the orbit. During endoscopic surgeryon these sinuses care is taken to avoid arteries passingfrom the orbit through the ethmoid sinuses into the nasalcavity. The orbit and its contents (particularly the opticnerve) are closely related to the nasal cavity. The pitu-itary gland (17) lies in its fossa in the sphenoid bone,just above the sphenoidal sinus (18).

Conchae (turbinates) and meati

The three conchae provide a large surface area, slowthe air flow, and make it turbulent. The superior (19)and middle (20) conchae are derived from the eth-moid. The inferior concha (21) is a separate bone,fused to the maxilla.

The meati are grooves that lie inferior to each con-cha. The spheno-ethmoidal recess (22) lies above thevariable superior concha to receive the sphenoidalsinus. The superior meatus (23) receives the posteriorethmoidal sinus and the inferior meatus (24) receivesthe nasolacrimal duct (25).

The middle meatus (26), under the middle concha,shows a bulge caused by the underlying ethmoid(bulla ethmoidalis) (27) and a semicircular grooveunder the bulge – hiatus semilunaris (29). The frontalsinus opens through the infundibulum anteriorly inthe hiatus, whereas the maxillary sinus opens posteri-orly. The anterior and middle ethmoid sinuses alsoopen into the middle meatus.

36 Head and Neck

1 Coarse hairs, vibrissae, in nostril2 Nasal bone3 Greater nasal cartilage4 Lateral nasal cartilage5 Nasal septum6 Position of vomer7 Position of perpendicular plate of

ethmoid bone8 Position of septal cartilage9 Frontal bone

10 Cribriform plate of ethmoid bone11 Sphenoid bone12 Horizontal plate of maxilla13 Horizontal plate of palatine bone14 Aperture of maxillary sinus15 Maxillary sinus16 Ethmoidal air cells17 Pituitary gland18 Sphenoidal sinus19 Superior nasal concha

20 Middle nasal concha21 Inferior nasal concha22 Spheno-ethmoidal recess23 Superior meatus24 Inferior meatus25 Marker within opening of

nasolacrimal duct26 Middle meatus27 Ethmoidal bulla28 Frontal process of maxilla

29 Semilunar hiatus30 Septal process (medial crus) of

greater nasal cartilage31 Opening of auditory (Eustachian)

tube32 Frontal sinus33 Roof of nasal cavity34 Hard palate35 Fibrofatty tissue

A Cartilages of the external nose (from the left)B Coronal section through the head (from the front)C Nasal septum (from the right)D Lateral wall of the nasal cavity and nasopharynx (from

the right)

E Lateral wall of the nasal cavity and semilunar hiatus(from the right)

F Lateral wall of the nasal cavity (from the right)

Nasal cavity, bones, sinuses, conchae and meati 37

A

B

C D

E F

2

28

9

1031

1718

18

11 1910

2320

2113 12 24

26

7

8

12

3424

1718

19

20

2131

3424

1

22

232521

1420 29

2227

23

18

31

17

13

631

5

114

3

3530

3332

34

21

20

26

24

515

16

S

PA

I

S

AP

I

S

AP

I

S

AP

I

S

AP

I

S

LR

I

Location of numbers: 1F; 2A; 3A; 4A; 5BC; 6C; 7C; 8C; 9C; 10CD; 11CD; 12CD; 13CD; 14E; 15B; 16B; 17DEF; 18CDEF; 19DF; 20BDEF; 21BDEF; 22EF;23DEF; 24BDEF; 25F; 26BD; 27E; 28A; 29E; 30A; 31CDEF; 32B; 33B; 34BEF; 35A.

Nasopharynx, auditory tube,neurovascular supply of nasalcavity and nasopharynx,maxillary nerve

Nasopharynx – The nasal cavity continuesposteriorly into the nasopharynx (1), which is alsolined by respiratory epithelium and is held open bythe pharyngobasilar fascia that arises from the bonesof the skull base. The left and right sides of thepharyngobasilar fascia fuse in the posterior midlineand attach to the pharyngeal tubercle about 1 cmanterior to the foramen magnum.

Auditory tube – Equalization of pressure in the mid-dle ear occurs via the auditory (Eustachian) tube (2)that connects the middle ear to the nasopharynx. Thetube has a bony part that passes through the petroustemporal bone and a cartilaginous part that liesbetween the greater wing of sphenoid and the petroustemporal bone. It enters the nasopharynx above thepharyngobasilar fascia. The cartilage forms a tubal emi-nence (3) and gives partial origin to muscles that ele-vate the pharynx and soft palate (salpingopharyngeus(4), levator palati (5) and tensor palati (6)). Whenthese muscles contract on swallowing, they open theauditory tube, facilitating the flow of air to and fromthe middle ear with consequent pressure equalization.

Tonsils – Clusters of lymphoid tissue are gatheredunder the mucous membrane on the posterior wall ofthe nasopharynx and around the opening of theauditory tube. These are the pharyngeal (adenoid) (7)and tubal (3) tonsils, which may enlarge followingchronic inflammation to obstruct the nasopharynx andauditory tube. The latter may result in recurrent andchronic middle ear infections.

Neurovascular supply of nasal cavity and naso -pharynx – Sense of smell is via the olfactory nerves(8,9) that arise in the mucous membrane covering theroof and superior aspects of the lateral walls of thenasal cavity and nasal septum. The nerves pass throughthe cribriform plate (10) to the olfactory bulbs (11).

Branches of both the ophthalmic (from internalcarotid) and maxillary (from external carotid) arteriesenter the nasal cavity, accompanying the nerves. Thereare rich vascular anastomoses, and nosebleeds (epis-

taxis) are common. Anteriorly, on the septum, thebranches from the anterior ethmoidal artery (oph-thalmic) anastomose with branches of the sphenopala-tine (maxillary). The anastomosis is augmented byincoming branches from the facial artery, and usuallyalso by branches ascending from the palate. This highlyvascular spot is Little’s area (12) and the most commonsite of epistaxis, which is treated by packing the nasal cav-ity. Occasionally the sphenopalatine artery (13), situatedposteriorly in the cavity may rupture and bleed profusely.Such haemorrhage may be difficult to control by packingalone and cauterization of vessels or even selective arte-rial embolization may have to undertaken.

The equivalent nerves are sphenopalatine and nasalbranches of the maxillary nerve posteriorly, and ante-rior ethmoidal branches of the nasociliary (a branch ofV1) anteriorly.

Maxillary nerve (V2) – The maxillary nerve is asensory nerve that has ‘picked-up’ postganglionicsecretomotor fibres from the pterygopalatineganglion. Before passing into the inferior orbitalfissure to become the infra-orbital nerve, themaxillary gives a zygomatic branch and the posterior,superior dental (alveolar) nerves. The latter, alongwith other superior dental nerves that arise from theinfra-orbital and pass in the wall of the maxillarysinus (giving the sinus its sensation and secretomotorsupply) provide sensation to the upper teeth.

The infra-orbital nerve itself emerges through theinfra-orbital foramen to provide sensation to the skinof the lower eyelid and upper lip, and underlying con-junctiva or mucous membrane. The zygomatic branchdivides within the orbit into two branches (zygomati-cofacial, zygomaticotemporal) that pierce the boneand emerge to give sensation to the skin over thecheekbone and temple, just around the eye. The zygo-maticotemporal branch carries the parasympatheticfibres that pass to the lacrimal nerve and give secreto-motor supply to the lacrimal gland. The sphenopala-tine and nasal branches carry sensation and secretomo-tor supply to the nasal cavity, both the lateral wall andseptum posteriorly. The pharyngeal branch carries thesame modalities to the nasopharynx.

The lesser and greater (22) palatine nerves arejoined by a few taste fibres. They pass down the pala-tine canal, and through the greater and lesser palatineforamina to supply the hard and soft palates.

38 Head and Neck

A B

C

D

E

10

13

12

2123

7

1

2714

8

20

1216

21

26

25

245

21

10

26

25

24

21

2223

27

37 6 5

4

9

11

171518

19

S

AP

I

S

AP

I

S

AP

I

S

AP

I

A

RL

P

1 Nasopharynx (nasal part ofpharynx)

2 Opening of auditory (Eustachian)tube

3 Tubal elevation and position oftubal tonsil

4 Salpingopharyngeus5 Levator veli palatini (levator palati)6 Tensor veli palatini (tensor palati)

7 Position of pharyngeal tonsil(adenoid)

8 Filaments of olfactory nerve (I)9 Olfactory nerve (I) filaments

passing through the cribriformplate of the ethmoid bone withindural sheaths

10 Cribriform plate of ethmoid bone11 Olfactory bulb

12 Position of Little’s area13 Position of sphenopalatine artery14 Position of olfactory bulb15 Olfactory tract16 Cut edge of nasal septum

mucosa17 Dura mater18 Optic nerve (II)19 Optic chiasma

20 Perpendicular plate of ethmoid21 Hard palate22 Greater palatine nerve and canal23 Pterygopalatine ganglion24 Inferior nasal concha25 Middle nasal concha26 Superior nasal concha27 Sphenoidal sinus

A Nasal septum (from the right)B Mucous membrane lining of the lateral wall of the nasal

septum (from the right)C Lateral wall of the nasal cavity (from the right)D Lateral wall of the nasal cavity, palatine canal (from the

right)E Cranial fossae with partial dissection of the left orbit

(from above)

Nasopharynx, auditory tube, neurovascular supply, maxillary nerve 39

Location of numbers: 1A; 2A; 3AD; 4D; 5CD; 6D; 7AD; 8B; 9E; 10AC; 11E; 12AB; 13A; 14B; 15E; 16B; 17E; 18E; 19E; 20B; 21ABCD; 22D; 23D; 24CD;25CD; 26CD; 27AD.

Temporomandibular joint andmuscles

The bony surfaces of the temporomandibular joint(TMJ) are lined by fibrocartilage instead of hyalinecartilage. The head of the mandible (1) articulateswith the mandibular fossa. The TMJ is divided into anupper and a lower joint by a fibrocartilaginous disc(2) that sits over the mandibular head, but alsoattaches to the joint capsule peripherally and into thesquamotympanic fissure posteriorly. The disc may dete-riorate, causing pain in the joint. The capsule attaches tothe articular margins (anterior to the articular tuber-cle) and thickens laterally as the strong, lateral tem-poromandibular ligament (3). There are two associ-ated ligaments that are separate from the joint: sphe-nomandibular, from spine of sphenoid to lingula ofmandible; stylomandibular (4), from styloid processto angle of mandible.

Movements of the temporomandibular joint

The inferior alveolar (dental) nerve enters the mandiblethrough the mandibular foramen, posteromedial to thelingula. To prevent stretching of the nerve during open-ing of the mouth, the axis of this movement passesthrough the lingulae. When opening the mouth, thehead of the mandible and its overlying disc are drawnforward and downward onto the articular tubercle (pro-trusion). There is associated rotation of the mandibularhead in relation to the disc for further mandibulardepression and wider opening of the mouth. Protrusiontakes place in the upper joint cavity, which is laxenough to allow this. As a result, it is possible to dislocatethe TMJ anteriorly if the mouth is opened too widely. Toclose the mouth, the head of the mandible and discmust be retracted back into the mandibular fossa, andthe mandible elevated by rotation.

When chewing food, the mandible tends to swingfrom side to side by the following repeated mecha-nism. The left mandibular head is held in the fossa.The right head is protruded, then retracted and held,while the left head is protruded and then retracted.During protrusion, as the head and disc slide down thearticular tubercle, the teeth separate. During chewingthis must be counteracted by rotatory mandibular ele-vation.

Muscles of mastication (all supplied by V3)

Opening the mouth. Lateral pterygoid (5) arises fromthe lateral aspect of the lateral pterygoid plate and theroof of the infratemporal fossa. The fibres pass poste-riorly to insert into the mandibular condyle, the cap-sule and the disc of the TMJ. The muscle draws thecondyle and disc forward and down the articulartubercle in protrusion. Lateral pterygoid is the onlyprimary muscle of mastication that opens the mouth.Muscles passing upward from the hyoid to themandible, in particular digastric (6), may assist it.

Closing the mouth. The three other primary musclesof mastication elevate the mandible in biting, chewingand grinding. Their resting tone maintains normal clo-sure of the mouth. Temporalis (7,8) arises from thetemporal fossa and overlying fascia. It passes deep tothe zygomatic arch to attach to the coronoid process(9) and anterior aspect of the mandibular ramus. Itsposterior, horizontal fibres retract the mandible. Theanterior ones are powerful elevators.

Masseter (10) passes from the zygomatic arch (11)to the lateral aspect of the mandibular ramus. Medialpterygoid (12) is a deeper, almost mirror image ofmasseter. It arises from the lateral pterygoid plate, butfrom its medial aspect. There is a small superficialhead from the maxilla. It inserts onto the medialaspect of the mandibular ramus. Both masseter andmedial pterygoid are powerful elevators of themandible and both aid protrusion as their fibres passslightly posteriorly as well as inferiorly.

The maxillary artery (13), a terminal branch of theexternal carotid, arises in the parotid gland to passanteriorly deep to the neck of the mandible (15). Inthe infratemporal fossa it sends branches to the masti-catory muscles, to the external acoustic meatus and tothe middle ear. The middle meningeal artery alsoarises here and pierces the auriculotemporal nervebefore entering the skull. The maxillary artery thensends branches to pass with all the branches of themandibular nerve, e.g. lingual (16) and inferior alveo-lar (17), before passing through the pterygomaxillaryfissure to enter the pterygopalatine fossa. It then sendsbranches with all those of the maxillary nerve andpterygopalatine ganglion.

40 Head and Neck

1 Head of mandible2 Articular disc of

temporomandibular joint3 Lateral ligament of

temporomandibular joint4 Stylomandibular ligament5 Lower head of lateral pterygoid6 Anterior belly of digastric

7 Temporalis8 Temporalis tendon9 Coronoid process of mandible

10 Masseter11 Zygomatic arch12 Medial pterygoid13 Maxillary artery14 Deep temporal artery

15 Neck of mandible16 Lingual nerve17 Inferior alveolar nerve18 Body of mandible19 Zygomatic bone20 Temporal bone21 Sternocleidomastoid22 External acoustic meatus

23 Ramus of mandible24 Posterior belly of digastric25 Styloid process26 Upper head of lateral pterygoid27 Buccinator28 Great auricular nerve

A Side of face, muscles of mastication (from the left)B Side of face, temporomandibular joint (from the left)

C Side of face, temporalis tendon (from the front and left)D Side of face, infratemporal fossa (from the left)

Temporomandibular joint and muscles 41

A

B

C

D

7

81919

7

8

915

3

23

6

1817

27

19 26

135

21

12

16

28

21

24

4

25

14

21

19

8

7

20

21

15

39

23

10

11

3

1510

22

20

21

S

PA

I

S

PA

I

S

PA

I

S

Lat(L)

M

I

Location of numbers: 1D; 2D; 3ABC; 4D; 5D; 6D; 7ABC; 8ABC; 9BC; 10AB; 11A; 12D; 13D; 14D; 15ABC; 16D; 17D; 18D; 19ABCD; 20AB; 21ABCD; 22A;23BC; 24D; 25D; 26D; 27D; 28D.

Face: skeleton, muscles; scalp

The face is dominated by the orbital, nasal and oralcavities, each having groups of sphincter and dilatormuscles. The muscles around the oral cavity areimportant when eating, and all the muscles insert intothe overlying skin as muscles of facial expression. Thescalp is essential for some facial expressions. Wordsand speech are formed by movement of the lips andcheeks as well as the tongue. Any injury affecting thefacial muscles or their nerve supply (VII) may well affectfacial movements and speech. Therefore the motor andsensory nerve supplies to this region are important in clin-ical examination.

Five layers of the scalp

1 – The skin (1) has hair and associated sebaceousglands, which may form cysts. Cutaneous nervesderived from the V1, V3 and the occipital nerves con-verge into the scalp from the periphery.

2 – The subcutaneous tissue connects the skin to theunderlying aponeurosis. It is dense, thick tissue with arich blood supply. The arteries anastomose freely fromboth sides and from branches of both the internal andexternal carotids. The rich anastomosis and dense con-nective tissue that tends to hold open a lacerated arterymeans scalp wounds bleed profusely. When carrying outneurosurgery the scalp must be lifted, usually on the vas-cular pedicle of the superficial temporal artery (10).Venous drainage from the forehead passes via oph-thalmic veins into the cavernous sinuses and forms a pos-sible route for spread of infection to those sinuses.

3 – Occipitalis (2) has a muscle belly on each side thatarises from the skull and inserts into the epicranialaponeurosis (3). The aponeurosis gives origin tofrontalis (4), which anteriorly attaches to the skin ofthe eyebrow. Laterally the aponeurosis thins andblends with the fascia over temporalis (6). Togetheroccipitalis and frontalis contract to raise the eye-brows. Frontalis contracts to frown or wrinkle theforehead.

4 – The loose connective tissue beneath the aponeuro-sis allows the scalp movement described above. It mayalso allow traumatic lifting of the scalp, e.g. should longhair be caught in machinery. Following wounds to thescalp foreign bodies may enter this layer.

5 – The periosteum (7) adheres to the bone and iscontinuous with the periosteal layer of dura mater atthe foramina and via the sutures.

Muscles around the oral cavity

Buccinator (12) compresses the cheeks to keep foodbetween the teeth when chewing. It arises from themaxilla and mandible, away from the alveolar bonethat supports the teeth. As the fibres pass backwardthey pass medially behind the upper and lower molarteeth to merge with the superior constrictor muscle ofthe pharynx and form the pterygomandibular raphethat ensures continuity of the cheeks and pharynx.

As the fibres of buccinator pass forward into the lipsthey form orbicularis oris (13). The central fibrescross each other so that lower central fibres go to theupper lip and upper central fibres to the lower lip,forming the modiolus (14) just lateral to the corner ofthe mouth. The upper and lower fibres of buccinatorpass into the upper and lower lips, respectively. As aresult, orbicularis oris encircles the lips and is thesphincter that keeps them closed when chewing.

The dilator muscles (15,16) meet at the modiolusand usually contribute to orbicularis oris. These fourmuscles have the actions implied by their names:levator and depressor anguli; levator and depressorlabii. Two (often variable) zygomatic muscles (17)arise from the zygoma and pass to the upper lip andangle of the mouth. Along with risorius, which arisesfrom the parotid fascia and goes to the skin of theangle of the mouth, they contribute to smiling andgrinning. Mentalis (18) pulls the skin upward to helpprotrude the lower lip in drinking and pouting.

Platysma (19) lies in the superficial fascia and ishighly variable. It passes from the upper thoracic wall,through the neck and into the lower lip, with a fewfibres attaching to the mandible. It depresses the lowerlip in a grimace and also prevents indrawing if thestructures in the neck during forced inspiratory effort.

42 Head and Neck

1 Skin and dense subcutaneoustissue

2 Occipitalis (occipital belly ofoccipitofrontalis)

3 Epicranial aponeurosis (galeaaponeurotica)

4 Frontalis (frontal belly of

occipitofrontalis)5 Bone of cranial vault6 Temporal fascia7 Loose connective tissue and

pericranium (periosteum)8 Masseter9 Orbicularis oculi

10 Superficial temporal artery11 Occipital artery12 Buccinator13 Orbicularis oris14 Modiolus15 Levator anguli oris16 Depressor anguli oris

17 Zygomaticus major18 Mentalis19 Platysma20 Sternocleidomastoid21 Parotid gland22 Zygomatic arch23 Facial nerve branches

A Cranial vault, stepped dissection (from above)B Side of face, superficial dissection (from the left)

Face: skeleton, muscles; scalp 43

A B

2

1 3 7 5

13

13

18 19

20

2

11

6

4

1 3

922

10

218

231214

16

17

15

23

23

4

S

PA

I

P

LR

A

Location of numbers: 1AB; 2AB; 3AB; 4AB; 5A; 6B; 7A; 8B; 9B; 10B; 11B; 12B; 13B; 14B; 15B; 16B; 17B; 18B; 19B; 20B; 21B; 22B; 23B.

Facial neurovascular supply,salivary glands

The facial nerve passes through the middle ear toemerge from the stylomastoid foramen. It suppliesoccipitalis (1), posterior belly of digastric and stylohy-oid before entering the parotid gland (2). It branchesvariably within the gland, but the more frequentappearance is of five branches splaying across the face:temporal (3) to frontalis; zygomatic (4) to orbicularisoculi; buccal (5) to buccinator and muscles of theupper lip; marginal mandibular (6) to muscles of thelower lip; and cervical (7) to platysma.

The marginal mandibular branch dips below themandible to overly the submandibular gland (8), where itis susceptible during gland surgery. Injury causes lower lipparalysis and saliva dribbles from the mouth. The mastoidprocess (9) is not formed at birth and the facial nerve maybe injured during forceps delivery. Similarly, the nerve maybe injured just before emerging from the stylomastoidforamen. Such diseases (Bell’s palsy) show weakness of allthe muscles from frontalis to platysma, on the ipsilateralside of the face. A cerebrovascular accident affecting onehalf of the brain will not affect the upper face, but willweaken the lower opposite facial muscles. Consequently, allaspects of facial muscle function must be clinically assessed.

Sensory nerve supply of the facial skin

The skin over the angle of the mandible (10) is sup-plied by C2,3 via the great auricular nerve (11). Theremainder is via branches of the trigeminal nerve:● Upper eyelid, forehead to vertex, root and tip of

nose – ophthalmic via lacrimal, supra-orbital, supra-trochlear and nasociliary.

● Lower eye lid, upper lip, upper cheek – maxillaryvia infra-orbital, zygomaticotemporal and zygo-maticofacial.

● Lower lip, chin, lower cheek, temporal region –mandibular via mental, buccal, and auriculotemporal.Each region of nerve distribution may be individually

affected by shingles or by trigeminal neuralgia and shouldbe tested individually. Shingles seen on the tip of the nosemay also affect the cornea as branches of the nasociliarynerve supply both. Sensory supply to eyelid, lip andcheek is the same for skin and underlying mucousmembrane.

Blood supply

The facial artery (12), branch of external carotid, ispalpable as it passes over the mandible, anterior tomasseter (13). The left and right facial arteries anasto-mose freely. Veins converge on the facial vein (14),which joins the internal jugular. There may be deepconnections to the cavernous sinus via the venousplexus around the pterygoid muscles (route for spreadof infection).

Salivary glands

Saliva wets and lubricates food; it also contains enzymesto commence digestion. Small salivary glands are scat-tered under the mucous membrane of the lips andcheeks, and the sublingual glands (Illustration G) lieunder the tongue, on the floor of the mouth. The parotid(Illustration F) secretes serous saliva, and the sub -mandibular (Illustration E) secretes seromucous saliva.

The parotid lies between the mastoid process andthe mandibular ramus. It overlaps sternocleido-mastoid (15) and masseter, and extends medially asfar as the styloid process (16). The facial nerve lies lat-eral to the retromandibular vein and external carotidartery within the gland, which is enclosed in deep fas-cia, therefore swelling of the gland and its associatedlymph nodes (mumps) is painful. The secretomotorsupply is from the glossopharyngeal, via the auriculo -temporal nerve. The parotid duct (17) crosses mas-seter where there may be a small accessory parotidlobe (18) superior to it. The duct pierces buccinator toenter the oral cavity opposite the second upper molartooth. It takes an oblique course through buccinator,creating a sphincteric affect.

The submandibular gland lies inferior to the body ofthe mandible, between it and mylohyoid (19). Itcurves around the posterior aspect of mylohyoid to liebetween it and hyoglossus (20). From this deeper partof the gland, the submandibular duct (21) passes for-ward (surrounded by the sublingual gland (22) andreceiving its ducts) to open on the sublingual papilla(40) on the lingual frenulum. The secretomotor sup-ply for both glands is via chorda tympani (VII), run-ning with the lingual nerve that winds inferior to, andthen medial to, the submandibular duct before passingupward to the tongue. Stones within the submandibularduct cause obstruction and painful swelling of the glandon salivation.

44 Head and Neck

1 Occipitalis (occipital belly ofoccipitofrontalis)

2 Parotid gland3 Temporal branches of VII4 Zygomatic branches of VII5 Buccal branches of VII6 Marginal mandibular branches

of VII7 Cervical branches of VII8 Submandibular gland9 Mastoid process

10 Angle of mandible11 Great auricular nerve12 Facial artery13 Masseter14 Facial vein15 Sternocleidomastoid16 Styloid process17 Parotid duct18 Accessory lobe of parotid gland19 Mylohyoid20 Hyoglossus

21 Submandibular duct22 Sublingual gland23 Geniohyoid24 External jugular vein25 Anterior belly of digastric26 Buccal fat pad27 Lesser occipital nerve28 Superficial temporal artery29 Auriculotemporal nerve30 Occipital artery31 Greater occipital nerve

32 Platysma33 Platysma (reflected)34 Lymph node35 Lingual artery36 Lingual nerve37 Genioglossus anterior part38 Body of mandible39 Maxillary artery40 Orifice of submandibular duct

(sublingual papilla)

A Side of face superficial dissection (from the left)B Skull with mandible (from the left) with outline position

of parotid gland and duct, and submandibular glandC Left side of face, submandibular region (from the left)D Deep dissection of the tongue (from the right)

E Left submandibular gland with outline position ofmandible (from above)

F Left parotid gland with outline position of mandible(from above)

G Left sublingual gland (from the right)

Facial neurovascular supply, salivary glands 45

A

E F G

C

D

B

12

326

213

1214

33

25

24

37

22

38

19

21

814

2

2221

40

39

18517

12

23

20

35

3621

8

34

6 11

15

7

11

15

27

213

26 17

5

18

28

29

34

1 30

10

9

16

31

S

PA

I

S

PA

I

M

PA

Lat (L)

M

PA

Lat (L)

S

PA

I

S

AP

I

S

AP

I

Location of numbers: 1A; 2ACF; 3A; 4A; 5AF; 6AC; 7A; 8CE; 9B; 10B; 11AC; 12ACE; 13AC; 14CE; 15AC; 16B; 17AF; 18AF; 19D; 20D; 21DEG; 22DG;23D; 24C; 25C; 26A; 27A; 28A; 29A; 30A; 31A; 32A; 33C; 34C; 35D; 36D; 37D; 38D; 39F; 40G.

Oral cavity, teeth, tongue

The maxillae (Illustration C, 1) and mandible(Illustration D, 2) support the oral cavity, for drinking,eating, chewing and speech. The oral cavity liesbetween the cheeks and lips, which are formed by skinand mucous membrane with muscle between. Theoral cavity proper is internal to the teeth. Thevestibule is outside the teeth and compressed by buc-cinator and orbicularis oris. Posteriorly, the cavity iscontinuous with the oropharynx (3). The hard (4)and soft (5) palates form the roof. The floor comprisesmylohyoid muscle (6), which arises from the inneraspect of the mandible to fuse with its neighbour inthe midline, forming a central raphe from mandible tohyoid (7). Further support and control of the floor ofthe mouth, and therefore the tongue, is provided bygeniohyoid (8), internal to mylohyoid, and by theanterior belly of digastric external to it.

Mylohyoid and hyoglossus (9) lie opposed to eachother. The lingual nerve (10), submandibular duct(11) and hypoglossal nerve (12) enter the oral cavitybetween them. The lingual artery (13) and glossopha-ryngeal nerve (14) enter deep to hyoglossus.

Infections, usually from tooth abscesses, may trackbackward in the fascial planes between the muscles, andthen around the pharynx or toward the larynx. Suchinfections require urgent treatment to prevent dangerousspread, or life-threatening laryngeal oedema.

Teeth

The teeth cut, tear and grind food. They are held bythe periodontal ligament in the alveolar bone at themargins of both jaws. Two identical sets of eight teethin each jaw makes thirty-two altogether. Third molars(wisdom teeth) may erupt at an angle causing impaction,necessitating extraction. Alveolar bone resorbs followingtooth loss or extraction.

Superior alveolar (dental) branches of the maxillaryand infra-orbital nerves supply the upper teeth andgums. The maxilla is relatively thin and anaestheticinjected into the gum will anaesthetize the dental nerves.As the superior alveolar nerves also supply the maxillarysinus, sinusitis may mimic toothache. The inferior alveo-lar (dental) branch of V3 supplies all the lower teethand then gives off the mental nerve through the men-

tal foramen to supply the skin of the chin, the lowerlip and its underlying mucous membrane. The inferioralveolar continues in the bone as the incisive nerve tothe incisor teeth, sometimes crossing the midline.Anaesthetic may be injected via the mental foramen toanaesthetize the incisive nerve. The buccal nerve suppliesthe gums lateral to the molars and must be anaesthetizeddirectly.

Tongue

The tongue is for manipulating food, and for speech.It is formed by muscles enclosed by mucous mem-brane continuous with the floor of the mouth and cov-ered with stratified squamous epithelium.

Intrinsic muscles run in different directions com-pletely within the tongue and alter its shape. Extrinsicmuscles pass into the tongue from surrounding bones,and alter its position during chewing and swallowing.Genioglossus (20) draws the tongue downward andforward. Hyoglossus pulls the sides of the tonguedownward. Palatoglossus and styloglossus pass down-ward and forward into the tongue from the palate andstyloid process, respectively. They pull the tongueupward and backward in swallowing.

Palatoglossus raises folds, one on each side, the pil-lars of the fauces (21). They separate the oral cavityfrom the oropharynx. While chewing, the pillarsapproximate to each other, and to the soft palate, toprevent food entering the pharynx, and possibly thelarynx during inspiration. The hypoglossal supplies allthe tongue muscles except palatoglossus, which is sup-plied by the pharyngeal plexus.

The mucous membrane under the tongue and on thefloor of the mouth is smooth, and its sensory supply isby the lingual nerve. The dorsum of the tongue isdivided by the sulcus terminalis (22) into anteriortwo-thirds and posterior one-third. The former is cov-ered by filiform papillae giving the tongue its ‘furry’appearance and helping grasp food. Fungiform papil-lae (23), with taste buds, are scattered around thetongue surface. The circumvallate papillae (24), alsowith taste buds, lie in front of the sulcus terminalis.The lingual nerve, which has the chorda tympani run-ning with it to supply taste sensation, supplies generalsensation to the anterior two-thirds. The posteriorone-third is supplied by glossopharyngeal for bothgeneral sensation and taste.

46 Head and Neck

A

B

C

D

14

5

28 22

23

25

27

2

103130

119

1314

7

6

121227

7

2

20

8

6

29

29

3233

34

35

36

37

38

3915

17

16

126

3

24

21

39

18

4019

3533

38

3736

3432

S

AP

I

A

LR

P

P

LR

A

S

AP

I

1 Maxilla2 Body of mandible3 Oropharynx (oral part of

pharynx)4 Hard palate5 Soft palate6 Mylohyoid7 Body of hyoid bone8 Geniohyoid9 Hyoglossus

10 Lingual nerve

11 Submandibular duct12 Hypoglossal nerve13 Lingual artery14 Glossopharyngeal nerve15 Horizontal plate of palatine

bone16 Incisive foramen17 Greater palatine foramen18 Retromolar fossa of mandible19 Mandibular foramen20 Genioglossus

21 Palatoglossal fold (pillars of fauces)22 Sulcus terminalis23 Fungiform papillae24 Vallate papillae25 Vallecula26 Nasopharynx (nasal part of

pharynx)27 Epiglottis28 Uvula29 Lip30 Tendon of digastric

31 Deep part of submandibulargland

32 Central incisor33 Lateral incisor34 Canine35 First premolar36 Second premolar37 First molar38 Second molar39 Third molar40 Angle of mandible

A Midline sagittal section through the mouth (from theright)

B Deep dissection of the floor of the mouth (from the right)C Skull, dentition (from below)D Mandible, dentition (from above)

Oral cavity, teeth, tongue 47

Location of numbers: 1AC; 2AB; 3A; 4A; 5A; 6AB; 7AB; 8A; 9B; 10B; 11B; 12B; 13B; 14B; 15C; 16C; 17C; 18D; 19D; 20A; 21A; 22A; 23A; 24A; 25A; 26A;27AB; 28A; 29A; 30B; 31B; 32CD; 33CD; 34CD; 35CD; 36CD; 37CD; 38CD; 39CD; 40D.

Soft palate, tonsils, pharynx

The palate is overlain by mucous membrane withstratified squamous epithelium. The sensory andsecretomotor supply is mainly via the greater andlesser palatine nerves, with the sphenopalatine anteri-orly.

The soft palate (1) is tensed during swallowing andelevated to lie in a ‘socket’ (created by a few circularfibres of palatopharyngeus) and separate the orophar-ynx (2) from the nasopharynx (3). It is formed by theaponeuroses of the tensor palati muscles. Each of thesearises from a fossa in the sphenoid, immediatelymedial to the foramen ovale (the emerging mandibu-lar nerve lies on the lateral surface of tensor palati).The muscle belly then lies between the lateral andmedial pterygoid plates. Its tendon hooks around thepterygoid hamulus at the inferior end of the medialpterygoid plate, and flares into a flat, triangularaponeurosis that attaches to the palatine bone anteri-orly and its neighbour from the opposite side medially.The aponeurosis is covered by a glandular mucousmembrane that forms the dependent uvula (4).Tensor palati is supplied by V3. Levator palati (5)arises within the pharynx from the apex of the petroustemporal bone and passes inferiorly to insert into thepalatine aponeurosis.

Tonsils

The lingual tonsil (6) lies under the mucous mem-brane of the posterior one-third of the tongue. Thepalatine tonsil (7) lies in the fossa behind palatoglos-sus, but in front of palatopharyngeus (8).

Tonsils are clusters of lymphocytes, but the overly-ing mucous membrane dips into the tonsillar tissue toform crypts. The lingual, palatine, pharyngeal andtubal tonsils form a protective lymphoid ring aroundthe entries to the respiratory and digestive tracts. Thebed of the palatine tonsil is highly vascular, receivingbranches from the facial artery. Occasionally, there canbe considerable bleeding during or following excision ofthe tonsil. The mucous membrane overlying the pala-tine tonsil is supplied by a plexus that includes themaxillary and glossopharyngeal nerves. The glossopha-ryngeal also supplies the middle ear therefore tonsillitismay refer pain to the middle ear.

Pharynx

The pharynx is for the passage of air from the nasalcavity to the larynx and trachea, and for food from theoral cavity to the laryngopharynx (9) and oesophagus.The oropharynx is a passage for food or air, dependingon the position of the soft palate. The pharyngobasilarfascia (10) holds the nasopharynx open, but the con-strictor muscles help squeeze a bolus of food inferiorlytoward the oesophagus.

Superior constrictor (11) arises from the medialpterygoid plate and the pterygomandibular raphe,which ensures continuity between it and buccinator.Middle constrictor (12) arises from the hyoid bone andstylohyoid ligament. Inferior constrictor arises from thethyroid and cricoid cartilages: thyropharyngeus (13)and cricopharyngeus (14). The constrictors sweeparound the pharynx and fuse in the pharyngeal raphe(15). They overlap each other and the pharyngobasilarfascia so that much of the pharynx has three layers inits wall. More inferiorly, there may be only middle andinferior constrictors, leaving a possible weakness in the walland the potential for the formation of a pharyngeal diver-ticulum (pouch). Cricopharyngeus forms a sphinctericring around the lower pharynx and is only open duringswallowing. Otherwise air would be sucked into theoesophagus during thoracic expansion for inhalation.

On swallowing, the pharynx is elevated to meet thebolus by muscles arising from the skull and descendingto merge with the constrictors and the mucous mem-brane. The site of origin is implied by their names: salp-ingopharyngeus (16) from the cartilage of the auditorytube; palatopharyngeus from the palate; stylopharyn-geus from the styloid process. Pharyngeal elevation alsocauses simultaneous elevation of the larynx, which isvital for laryngeal closure, and the prevention of foodor fluid entering the airway during swallowing.

The pharyngeal plexus gives sensory supply to theoropharynx and motor supply to all the above musclesexcept tensor palati (V3) and stylopharyngeus (IX).The plexus is composed of: sensory fibres from theglossopharyngeal; sympathetic fibres from the sympa-thetic trunk; somatic motor and parasympatheticsecretomotor fibres from the vagus. Sensation to themucous membrane of the pharynx is supplied by: thepharyngeal branch of the maxillary, to nasopharynx;the glossopharyngeal via the pharyngeal plexus, tooropharynx; the vagus, to laryngopharynx.

48 Head and Neck

A

B

C

179

2

4

1

5

17

10

11

1512

13

14

1922

2118

20

6

816

1

4

3

9

2

7

3

S

AP

I

S

AP

I

S

RL

I

1 Soft palate2 Oropharynx (oral part of pharynx)3 Nasopharynx (nasal part of

pharynx)4 Uvula5 Position of levator veli palati

(tensor veli palatini)

6 Lingual tonsil7 Palatine tonsil8 Palatopharyngeus9 Laryngopharynx (laryngeal part

of pharynx)10 Pharyngobasilar fascia11 Superior constrictor

12 Middle constrictor13 Thyropharyngeus part of inferior

constrictor14 Cricopharyngeus part of inferior

constrictor15 Posterior, midline, pharyngeal

raphe

16 Position of salpingopharyngeus17 Epiglottis18 Internal jugular vein19 Common carotid artery20 Internal carotid artery21 Vagus nerve (X)22 Sympathetic chain

A Mouth and pharynx(from the right)

B Mouth and pharynx(from the right)

C Pharynx (from behind)

Soft palate, tonsils, pharynx 49

Location of numbers: 1AB; 2AB; 3AB; 4AB; 5A; 6B; 7B; 8B; 9AB; 10C; 11C; 12C; 13C; 14C; 15C; 16B; 17AB; 18C; 19C; 20C; 21C; 22C.

Larynx, trachea

The inlet of the larynx is a sphincter to protect theairway. The vocal cords act in phonation, coughing,sneezing and raising intra-abdominal pressure. Like allconductive parts of the airway, the larynx must beheld open. Other functions depend on alteration ofthe airway diameter, so the larynx is composed offibro-elastic membranes suspended between cartilagesjoined to each other and controlled by muscles. Thepassages are lined by respiratory epithelium.

The laryngeal inlet opens posteriorly and slightlysuperiorly into the pharynx. The piriform fossae (1)lie between the sidewalls of the larynx and of thepharynx. The valleculae lie between the tongue andthe epiglottis (2). Foreign bodies may be caught in thevalleculae and/or piriform fossae.

The hyoid bone (3) is attached to the superior horn(4) of the thyroid cartilage. The laryngeal cartilagesare all hyaline, except the epiglottis, which is elastic.The thyroid cartilage (5) has a notch (6) superiorly. Itis palpable in the neck, as is the hyoid, and both maybe felt moving upward on swallowing. The epiglottisattaches to the thyroid cartilage and extends upward,anteriorly in the larynx and pharynx, but posterior tothe tongue. During swallowing it is pushed backwardlike a lid over the closed laryngeal inlet. The epiglottisis not essential for laryngeal closure.

The cricoid cartilage has a lamina (7) and an arch(8). It is the only complete ring in the airway. The ary-tenoid cartilages (9) are pyramidal, and sit on the‘shoulders’ of the cricoid lamina. Both have an ante-rior, vocal process that extends into the vocal fold (10)and a lateral, muscular process (11), for insertion ofsome of the muscles that move them.

Laryngeal membranes

The thyrohyoid membrane lies between the hyoidbone and the thyroid cartilage. The internal laryngealbranches of the superior laryngeal neurovascular bun-dle pierce it. The quadrangular membrane has anupper edge, the aryepiglottic fold, running upwardobliquely from the arytenoid to the epiglottis. Thisfold, with its neighbour on the other side, forms thelaryngeal inlet. The lower edge of the quadrangular

membrane runs from the arytenoid to the thyroid car-tilage to form the vestibular or false vocal fold (12).

The cricothyroid membrane is suspended betweenthe cricoid and thyroid cartilages, but extends upwardto the vocal process of the arytenoid. Its upper freeedge passes from the vocal process to the thyroid car-tilage as the true vocal fold. The lower edge fuses withthe cricoid ring. Anteriorly the cricothyroid mem-branes fuse and are palpable between the thyroid andcricoid cartilages. Laryngeal inflammation and conse-quent oedema may completely obstruct the airway. Thisis life-threatening and must be rapidly recognized so thatan opening may be made urgently below the obstruction(cricothyroidotomy (13)).

The ventricle or sinus of the larynx lies between thevestibular and vocal folds. Here the mucous mem-brane bulges upward as a saccule outside the quadran-gular membrane. The saccule is lined by mucus-secret-ing epithelium to lubricate the vocal folds.

Trachea

The trachea continues from the larynx at C6, throughthe neck into the thorax where it divides to form theright and left main bronchi to carry air to and from thelungs. It is a fibro-elastic and muscular tube, held openby sixteen to twenty C-shaped rings of hyaline carti-lage (14) and lined by respiratory epithelium.Cigarette smoking paralyses the cilia, debilitating the nor-mal mechanism of mucus removal from the respiratorysystem.

The C-shaped cartilages are deficient posteriorlywhere the trachea is related to the oesophagus – theirends joined by trachealis (15) muscle to control tra-cheal diameter. It is narrowed in coughing and todecrease respiratory dead space, but opens to facilitateimproved airflow. The elasticity of the trachea allowsstretching during swallowing or inhalation, followedby elastic recoil.

Tracheostomy (16) is carried out electively by remov-ing parts of the second and third tracheal cartilages. Caremust be taken to avoid the inferior thyroid veins that passinferiorly in the midline.

Tracheal blood supply is via inferior thyroid andbronchial vessels. Lymph drains to tracheobronchialand paratracheal nodes. Sensory and secretomotorsupply is via the recurrent laryngeal nerves.

50 Head and Neck

A B C

D

2

3

419

6 5

26

13

8

14

16

20

17

18

1717

13

22

183

25

26

4

19

5

20

8

14

18

25

4

5

9

11

23 7 24

121

22

14

15

3

218

25

4 2221

9

7

10

125

17

S

LR

I

S

RL

I

A

RL

P

S

PA

I

1 Piriform fossa (recess)2 Epiglottis3 Body of hyoid bone4 Superior horn of thyroid

cartilage5 Lamina of thyroid cartilage6 Thyroid notch

7 Lamina of cricoid cartilage8 Arch of cricoid cartilage9 Arytenoid cartilage

10 Vocal ligament (true vocal cord)11 Muscular process of arytenoid

cartilage12 Vestibular fold (false vocal cord)

13 Site of cricothyroidotomy14 First tracheal ring15 Trachealis16 Site of tracheostomy17 Lesser horn of hyoid bone18 Greater horn of hyoid bone19 Median thyrohyoid membrane

20 Inferior horn of thyroid cartilage21 Corniculate cartilage22 Cuneiform cartilage23 Cricothyroid joint24 Crico-arytenoid joint25 Lateral thyrohyoid ligament26 Laryngeal prominence

A Hyoid bone and cartilages ofthe larynx (from the front)

B Hyoid bone and cartilages ofthe larynx (from behind)

C Hyoid bone and cartilages ofthe larynx (from the left)

D Hyoid bone and cartilages ofthe larynx (from above andbehind)

Larynx, trachea 51

Location of numbers: 1B; 2ABCD; 3ACD; 4ABCD; 5ABCD; 6A; 7BD; 8AC; 9BD; 10D; 11B; 12D; 13AC; 14ABC; 15B; 16A; 17ABCD; 18ABCD; 19A; 20AC;21BD; 22BD; 23B; 24B; 25BCD; 26AC.

Laryngeal muscles

The extrinsic laryngeal muscles attach the larynx toneighbouring structures and are important laryngealelevators. The hyoid bone attaches to the larynx, andthe pharyngeal inferior constrictor (8) arises from thelaryngeal cartilages, so any muscles that elevate thehyoid and pharynx will elevate the larynx.

During swallowing the laryngeal inlet must close.The tongue is pulled upward and backward to tip thebolus into the pharynx. The pharynx and larynx areelevated. Geniohyoid pulls the larynx slightly forwardas well as upward, therefore, it is effectively pulledupward under the back of the tongue. This is the maincontributor to closure of the laryngeal inlet. Theintrinsic muscles alter the diameters within the larynx:open or close the inlet; open or close the vocal folds;lengthen or shorten the vocal folds.

The inlet is closed by laryngeal elevation, aided bythe oblique arytenoid (9) continuing as aryepiglotti-cus (10). This muscle arises from the muscular processof one arytenoid, passes upward and medially to windaround the apex of the other arytenoid, and pass in thearyepiglottic fold to the epiglottis. Contraction ofthese two muscles draws the arytenoids, epiglottis andaryepiglottic folds together in a ‘purse string’ mecha-nism to close the inlet. The inlet opens or widens byelastic recoil in the trachea, and gravity causing the lar-ynx to fall inferiorly after swallowing. Thyro-epiglotti-cus arises from inside the thyroid cartilage to passupward and medially into the quadrangular mem-brane. It pulls the aryepiglottic folds open.

Opening (abduction) of the vocal fold is by poste-rior crico-arytenoid (11), which arises from thecricoid cartilage and inserts into the muscular processof the arytenoid. It has two actions, to pull the ary-tenoid laterally down the shoulders of the cricoid, andto rotate the muscular process posteriorly so that thevocal process swivels laterally. The two actions openthe rima glottidis, the space between the vocal folds.Closure (adduction) of the vocal fold is by two mus-cles, to counteract the two actions of posterior crico-arytenoid. Transverse arytenoid (12) pulls the two

arytenoids medially. Lateral crico-arytenoid passesfrom the cricoid arch to the muscular process of thearytenoid. It pulls the process anteriorly, to swivel thevocal process medially.

Lengthening of the vocal fold is by cricothyroid(13), which lies between the cricoid arch and the thy-roid lamina. It rocks the thyroid forward to increasethe distance between it and the arytenoid, thereforeincreasing vocal fold length to raise the pitch of thevoice. Shortening the vocal fold to decrease the pitchis by thyro-arytenoid, which lies within the vocal foldand draws the thyroid and arytenoid toward eachother. Vocalis is a subsidiary muscle within the vocalfold and alters its thickness.

All the laryngeal muscles are supplied by the recur-rent laryngeal nerve (X), except cricothyroid (externalbranch of the superior laryngeal nerve (X)). Therecurrent laryngeal also supplies sensation to the vocalfolds and the larynx below them. It lies intimatelyrelated to, and often entwined with, branches of theinferior thyroid artery. Great care must be taken to pro-tect this nerve during thyroid surgery. Complete transec-tion of the recurrent laryngeal paralyses the vocal fold,which then lies in a semi-abducted (cadaveric) position.The other fold compensates and speech may be weak-ened. There is little other effect. Should both nerves betransected, both cords are paralysed and lie in the semi-abducted position. Speech, coughing and raising theintra-abdominal pressure become impossible. Shouldboth nerves be bruised or partially injured it is said thatthe vocal fold adductors take over and the cords adductto the midline, completely closing the airway, makingcricothyroidotomy essential. The superior laryngeal nerveis close to the superior thyroid artery and again careshould be taken during surgery. Damage to the externalbranch paralyses cricothyroid causing some hoarseness ofthe voice. Damage to the internal branch causes loss ofsensation above the vocal folds.

Laryngeal blood supply is by branches of the supe-rior and inferior thyroid arteries and veins. Lymphdrains to deep cervical and paratracheal nodes.Laryngeal carcinoma is not uncommon and any alter-ations to the voice must be investigated.

52 Head and Neck

A

B

C

28

2

14

36

8

134

36

36

30

32

31

35

511

812

9

1

33

1034

29

2123

2516

20

8

13

14

26

22

3 619

18

2417

7

27

15

S

PA

I

S

LR

I

S

RL

I

1 Aryepiglottic fold2 Body of hyoid bone3 Lamina of thyroid cartilage4 Arch of cricoid cartilage5 Lamina of cricoid cartilage6 Thyrohyoid7 Stylohyoid8 Inferior constrictor9 Oblique arytenoid

10 Aryepiglotticus

11 Posterior crico-arytenoid12 Transverse arytenoid13 Cricothyroid14 Laryngeal prominence15 Submandibular gland (reflected

superiorly)16 Hypoglossal nerve17 Nerve to thyrohyoid18 Superior thyroid artery19 Superior laryngeal artery

20 Bifurcation of common carotidartery

21 External carotid artery22 Internal carotid artery23 Facial artery24 Internal laryngeal nerve25 Lingual artery26 Vagus nerve27 Anterior belly of digastric28 Angle of mandible

29 Piriform fossa (recess)30 Inferior horn of thyroid cartilage31 Superior horn of thyroid

cartilage32 Greater horn of hyoid bone33 Epiglottis34 Vestibule of larynx35 Trachealis36 First tracheal cartilage

A Side of face, submandibular region and larynx (from theleft)

B Larynx (from the front)C Larynx (from behind)

Laryngeal muscles 53

Location of numbers: 1C; 2B; 3AB; 4B; 5C; 6AB; 7A; 8ABC; 9C; 10C; 11C; 12C; 13AB; 14AB; 15A; 16A; 17A; 18A; 19A; 20A; 21A; 22A; 23A; 24A; 25A;26A; 27A; 28A; 29C; 30C; 31C; 32C; 33C; 34C; 35C; 36BC.

Superficial anterolateral neck,muscles, fascia

The neck is filled with many important structures thatpass between two of three regions: head and neck;upper limb; thorax. The neck is described in triangles.The posterior triangle is between trapezius and sterno -cleidomastoid, with the clavicle as its base. The ante-rior triangle is upside down, between sterno -cleidomastoid and the midline, with the body of themandible as its base.

Trapezius (1), supplied by the accessory nerve (2),extends the neck, shrugs the shoulders, and helpsscapular rotation during abduction of the upper limb.Sternocleidomastoid (3) (accessory nerve) is aprominent feature of the lateral neck. It is relatedsuperficially to the external jugular vein (4) anddeeply to the internal jugular vein (5) in the carotidneurovascular bundle. The muscle arises by sternal (7)and clavicular (8) heads from the manubrium andfrom the medial part of the clav icle. These two headsand the intervening fossa may be clearly visible.Sternocleidomastoid attaches to the mastoid processand superior nuchal line on the skull. Acting alone, itlaterally flexes the neck to tilt the ear to the ipsilateralshoulder. But it rotates the face in the opposite direc-tion. Such a position (wry neck) may be seen followinginjury to sternocleido mastoid, or to its nerve supply.Acting together (and with other neck muscles) thetwo sternocleido mastoids extend the head on theflexed neck, e.g. when straining to look over the headsof a crowd.

The three scalene muscles, anterior, medius (9) andposterior (10), lie in the floor of the posterior triangle.They pass from the cervical transverse processes to thefirst and second ribs. Consequently, they support theupper thorax during respiration, aiding thoracic eleva-tion in forced inspiration, and they laterally flex theneck. Inferiorly and more deeply, the subclavianartery, surrounded by the trunks of the brachialplexus, emerges between scalenus anterior andscalenus medius.

Levator scapulae (11) passes from the transverseprocesses of the upper cervical vertebrae to the upperangle of the scapula and helps to elevate and steady

the scapula. It is supplied segmentally by cervicalventral rami and by the dorsal scapular nerve. Theaccessory nerve runs along it in the fascia that formsthe roof of the posterior triangle. Splenius capitis(12), arising from the lower cervical and upper tho-racic spines, and passing to the mastoid process andsuperior nuchal line, rotates the head and, as part oferector spinae, is supplied by the upper cervical dorsalrami.

Cervical fascia and spaces

Structures within the neck move in relation to eachother, and to the vertebral column, during swallowingand movement of the head. Therefore the structuresare surrounded by layers of fascia with potential spacesin between.

The superficial fascia contains subcutaneous fat.Posteriorly the fat is loculated and may be the site ofabscesses or carbuncles. Anteriorly it includes platysmamuscle. The deep fascia has a series of components.The investing layer of deep fascia forms a supportivecollar around the neck. It attaches to the skull,mandible, clavicle and scapular spine, and splits toenclose sternocleidomastoid and trapezius. The pre-vertebral fascia overlies the anterior vertebral muscles(longus capitis and longus colli) and covers the scalenemuscles before fading out laterally over levatorscapulae. It passes from the skull base into the thorax,to fuse with the vertebral column at T3–4.

The carotid sheath passes from the skull to the aor-tic arch and encloses the common and internal carotidarteries, the internal jugular vein and the vagus nerve.It is loose over the vein to allow its distension. Thepretracheal fascia passes from the hyoid bone and thy-roid cartilage, inferiorly as far as the aortic arch. Itsplits to enclose the thyroid gland.

The potential spaces between the layers of fascia mayform the ‘line of least resistance’ for the spread of infec-tion, particularly from facial or oral structures. Theretropharyngeal space, behind the pharynx andoesophagus extends throughout the neck and poste-rior thorax from skull to diaphragm. The pretrachealspace is in front of the pretracheal fascia and extendsfrom the neck, behind the manubrium to the anteriormediastinum and aortic arch.

54 Head and Neck

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1 Trapezius2 Accessory nerve (spinal part or

root)3 Sternocleidomastoid4 External jugular vein5 Interior jugular vein6 Clavicular part of pectoralis

major7 Sternal head of

sternocleidomastoid

8 Clavicular head ofsternocleidomastoid

9 Scalenus medius10 Scalenus posterior11 Levator scapulae12 Splenius capitis13 Cervical nerves to trapezius14 Parotid gland15 Submandibular gland (unusually

low)

16 Clavicle17 Great auricular nerve18 Transverse cervical nerve19 Lesser occipital nerve20 Sternocostal part of pectoralis

major21 Anterior belly of digastric22 Platysma (reflected superiorly)23 Common carotid artery24 Omohyoid

25 Sternothyroid26 Jugulodigastric lymph node27 Prevertebral fascia28 Body of mandible29 Supraclavicular nerves30 Facial artery31 Anterior jugular vein

A Anterior triangle of neck (from the front and left)B Posterior triangle of neck (from the left and above)

Superficial anterolateral neck, muscles, fascia 55

Location of numbers: 1B; 2B; 3AB; 4AB; 5AB; 6AB; 7AB; 8AB; 9B; 10B; 11B; 12B; 13B; 14A; 15A; 16A; 17A; 18AB; 19B; 20AB; 21A; 22A; 23A; 24A; 25A;26A; 27A; 28A; 29B; 30A; 31A.

Strap muscles, thyroid andparathyroid glands

Strap muscles

The hyoid bone (1) is U-shaped, lies anteriorly in theneck and is palpable just above the thyroid cartilage. Itgives origin to muscles that contribute to the pharynx,the tongue and the floor of the mouth. Fine controlover the position of the hyoid bone and larynx withconsequent control of the position of the tongue, floorof mouth and mandible are essential during speech,swallowing and chewing.

The suprahyoid muscles that connect the hyoid tothe mandible (mylohyoid, geniohyoid) and skull areessential to these mechanisms, as are the infrahyoidstrap muscles that connect the hyoid bone and thyroidcartilage to the manubrium of the sternum (2) andclavicle (3) (sternohyoid (4), sternothyroid (5)), tothe scapula (omohyoid (6)) and to each other (thyro-hyoid). The infrahyoid muscles are supplied by theansa cervicalis, a nerve loop derived from C1–3.

Digastric (8) passes from the mandible to the mas-toid process as two bellies connected by an intermedi-ate tendon that passes through a fascial sling attachedto the hyoid. The posterior belly is supplied by thefacial nerve (cranial nerve VII) and the anterior bellyby the nerve to mylohyoid, from the inferior alveolarbranch of the third (mandibular) division of thetrigeminal nerve (V3).

With the hyoid held down by the strap muscles infe-rior to it, digastric is important for pulling themandible downward to open the mouth. Stylohyoid(VII) is not one of the strap muscles but it lies along-side the posterior belly of digastric and helps controlthe position of the hyoid.

Thyroid and parathyroid glands

The thyroid gland (Illustration B, 12) lies anteriorly inthe lower neck, between the carotid neurovascularbundles, clasping the trachea and the inferior aspect ofthe larynx. It is a ductless endocrine gland that secretesthyroxin and thyrocalcitonin. The former maintainsbasal metabolic rate and the correct function anddevelopment of many of the body tissues. The latter

lowers serum calcium by inhibiting its mobilizationfrom bone.

The shape of the thyroid is variable, but it usuallyhas right and left lobes, united across the second, thirdand fourth tracheal rings by an isthmus (13).Occasionally a pyramidal lobe extends superiorly fromthe isthmus. The gland is surrounded by pretrachealfascia that effectively attaches it to the thyroid carti-lage. As a result, the thyroid gland moves with the lar-ynx on swallowing. This attachment also prevents thethyroid from enlarging upward; any enlargement mustbe lateral and inferior, possibly even into the anteriormediastinum.

The parathyroid glands (Illustration C, 15) liewithin the thyroid capsule and are variable in numberand in position. There are usually four glands, withtwo each applied to the posterior aspect of each thy-roid lobe, one near the upper and one near the lowerpole. They secrete parathormone, which mobilizescalcium from the bone to raise serum calcium.Consequently, the parathyroids are necessary for life.

The thyroid and parathyroids are highly vascular andsupplied by the superior thyroid branch (16) of theexternal carotid artery, and the inferior thyroid branchof the subclavian (thyrocervical trunk). There is con-siderable anastomosis between the left and right arter-ies and between the superior and inferior arteries. Ananastomotic channel between the latter two passesclose to the parathyroids and is a landmark for theirsurgical location. The arteries are related to the laryn-geal nerves. Close to the gland the recurrent laryngealnerve often passes between branches of the inferior thy-roid artery. Therefore the inferior thyroid artery must beligated away from the gland. The superior laryngeal nerveis initially close to the superior thyroid artery but separatesfrom it nearer the gland. Therefore the superior thyroidartery should be ligated close to the gland.

The glands are drained by three veins on each side.The superior and middle veins pass to the internaljugular vein. The inferior thyroid vein (17) may beplexiform and pass to the left brachiocephalic. Lymphdrainage is to the deep cervical lymph nodes. Nervesupply is sympathetic, vasomotor, carried on the arter-ies and derived mainly from the middle cervical gan-glion.

56 Head and Neck

1 Body of hyoid bone2 Manubrium of sternum3 Clavicle4 Sternohyoid5 Sternothyroid6 Omohyoid7 Internal jugular vein

8 Anterior belly of digastric9 Subclavian vein

10 Subclavian artery11 Brachial plexus12 Lateral lobe of thyroid gland13 Isthmus of thyroid gland14 Vagus nerve

15 Left superior parathyroid gland16 Superior thyroid artery and vein17 Inferior thyroid vein18 Common carotid artery19 Sternocleidomastoid20 Subclavius21 Deltoid

22 Parotid gland23 Submandibular gland24 Facial artery and vein25 Body of mandible26 First rib27 Left lung apical lobe

A Neck deep dissection (from the left and slightly below)B Thyroid gland (from above) with outline of the position

of the tracheaC Left superior parathyroid gland (from the right)

Strap muscles, thyroid and parathyroid glands 57

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Location of numbers: 1A; 2A; 3A; 4A; 5A; 6A; 7A; 8A; 9A; 10A; 11A; 12AB; 13B; 14A; 15BC; 16ABC; 17AB; 18A; 19A; 20A; 21A; 22A; 23A; 24A; 25A;26A; 27A.

Deep anterolateral neck, thoracicinlet, arteries, vagus nerves

Deep within the neck, neurovascular structures passbetween the neck and the thorax or between theupper limb and the thorax. The first thoracic vertebra,manubrium and first ribs form the thoracic inlet thatslopes antero-inferiorly, following the slope of the firstrib (1). Scalenus anterior (2) is an important land-mark. The apex of each lung (3) extends up to theneck of the first rib. Therefore, the apex is above theanterior end of the first rib, and the medial end of theclavicle (4). Structures in the root of the neck, or tho-racic inlet, are related to the apex of the lung andpleura.

The brachiocephalic trunk (5) ascends to the rightof the trachea (6) to divide into the right commoncarotid (7) and the right subclavian (8) artery. On theleft the equivalent arteries (9,10) arise directly fromthe aortic arch.

Subclavian artery and its branches

The subclavian passes upward, medial to the apex ofthe lung and pleura, then laterally, anterior to the api-cal pleura and suprapleural membrane (first part), pos-terior to scalenus anterior (second part) to curve overthe first rib (third part) and enter the axilla as the axil-lary artery (11). It has branches only from the first andsecond parts. The vertebral artery enters the transverseforamen of the sixth cervical vertebra. It ascends in thetransverse foramina, surrounded by a plexus of veins,and a sympathetic plexus from the inferior cervicalganglion, to emerge and pass behind the lateral mass ofthe atlas to enter the foramen magnum.

The thyrocervical trunk divides into three branches.The transverse cervical and suprascapular arteries passabove the clavicle and across the brachial plexus. Theybranch to supply the muscles of the neck and alsothose around the scapula. These latter branches con-tribute to the scapular anastomosis, which is com-pleted by branches derived from the axillary artery.The inferior thyroid artery (12) takes a tortuouscourse, deep to the carotid sheath, behind the middlecervical ganglion (from which it picks up sympathetic

fibres) to the lower pole of the thyroid gland, where itis related to the recurrent laryngeal nerve. The inferiorthyroid supplies the pharynx and larynx. It also givesoff the ascending cervical artery that runs parallel tothe phrenic nerve and sends branches to nearby mus-cles and through the intervertebral foramina to thespinal cord.

The internal thoracic (mammary) artery (13) passesinto the thorax to run behind the costal cartilages.

The costocervical trunk divides into two branches:the deep cervical supplies the posterior neck muscula-ture, whereas the highest intercostal descends anteriorto the neck of the first rib to provide the posteriorintercostal arteries to the first and second spaces.

Carotid arteries

The common carotid arteries lie in the carotid sheathand divide into the external and internal carotid arter-ies at the upper border of the thyroid cartilage, whichis at the lower border of C3 vertebra.

The internal carotid continues upward to enter theskull via the carotid canal and supplies the brain andorbit. The external carotid divides to supply the face,scalp, oral and nasal cavities.

The carotid sinus (a baroreceptor for the control ofblood pressure) is a dilatation at the bifurcation of thecommon carotid, extending to the root of the internalcarotid. The carotid body (a chemoreceptor sensitiveto low oxygen or high carbon dioxide concentrationsin the blood) lies adjacent to the sinus, often wedgedbetween the internal and external carotids. The glos-sopharyngeal and vagus nerves supply both the sinusand the body.

Vagus nerves

The left and right vagus nerves (X) pass inferiorly inthe carotid sheath. Both vagi pass behind the brachio-cephalic vein and anterior to the subclavian artery. Asthe right vagus passes the subclavian it gives the rightrecurrent laryngeal nerve that then passes behind thecarotid artery to the larynx. The left vagus (15) passeswith the left carotid and left subclavian to lie on thearch of the aorta. In the neck both vagus nerves giveoff cardiac branches, as well as pharyngeal andsuperior laryngeal branches.

58 Head and Neck

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1 First rib2 Scalenus anterior3 Apex of lung4 Clavicle5 Brachiocephalic trunk

(innominate artery)

6 Trachea7 Right common carotid artery8 Right subclavian artery9 Left common carotid artery

10 Left subclavian artery11 Axillary artery

12 Inferior thyroid artery13 Internal thoracic (mammary)

artery14 Lateral lobe of thyroid gland15 Left vagus nerve16 Right phrenic nerve

17 Brachial plexus18 Sternocleidomastoid

A Deep dissection of the neck and great vessels (from thefront)

Deep anterolateral neck, thoracic inlet, arteries, vagus nerves 59

Deep anterolateral neck, veins,nerves

Veins

The jugular venous system drains the head and neck,and is variable.

The external jugular (6) forms opposite the angle ofthe mandible (or ear lobe) from the posterior auricu-lar vein (draining scalp behind ear) and the posteriorbranch of the retromandibular vein (formed by themaxillary and superficial temporal veins). It may bevisible as it descends superficial to sternocleido -mastoid, toward the middle of the clavicle, to enterthe subclavian (7) and it has a valve at its terminationand one more proximally. It may be used for venousaccess, but care must be taken to avoid introducing airemboli. Structures in the posterior triangle, the neck,and the scapular muscles usually drain to the externaljugular via the variable posterior jugular, supra-scapular and transverse cervical veins (11).

Anterior jugulars may be present, one on each sideof the midline, superficially. When present, they uniteto form the jugular venous arch above the suprasternalnotch. The arch passes laterally deep to sternomastoidto enter the external jugular.

The internal jugular (12) receives venous drainagefrom the intracranial structures (including orbital,nasal and oral cavities), the pharynx, larynx, thyroidgland and face. It lies in the carotid sheath, anterolat-eral to the internal and then the common carotidartery (13) and commences as the superior jugularbulb in the jugular foramen. It ends at the inferiorbulb by joining the subclavian to become the brachio-cephalic vein. There is a valve at its termination. Thesurface marking is from lobe of ear to sternoclavicularjoint. A jugular venous pressure wave may be visible justabove the clavicle in a patient lying at 45 degrees, partic-ularly in cardiac failure.

The subclavian is the continuation of the axillaryvein from the upper limb. It lies parallel to the subcla-vian artery (14), but more anteriorly and medially,crossing the first rib in front of scalenus anterior (15).The vein may be used for the insertion of central venouslines. Its close proximity to the apex of the pleura andlung makes pneumothorax a common complication ofthis procedure.

The brachiocephalic vein (internal jugular and sub-clavian) is formed deep to the sternoclavicular joint.The left vein passes to the right, behind themanubrium and thymus, above the aortic arch, to jointhe right brachiocephalic and form the superior venacava deep to the first right costal cartilage. Theyreceive their respective vertebral, internal thoracic,inferior thyroid and highest intercostal veins. The leftalso receives the left superior intercostal vein, whichdrains the left second and third intercostal spaces. Ifthe left brachiocephalic lies in a high position it may be atrisk during tracheostomy.

Lymph trunks

On the right the jugular, subclavian and mediastinallymph trunks drain into the right brachiocephalicvein. On the left these trunks usually combine to enterthe thoracic duct that enters the junction of the leftinternal jugular and left subclavian veins. The trunksmay enter separately.

Nerves

The sympathetic trunks (17), one on each side, ascendfrom the thorax to lie on the prevertebral muscles(18), posterior and medial to the carotid artery. Eachtrunk has a superior ganglion that extends from theskull base to opposite the angle of the mandible, amiddle ganglion, and an inferior ganglion that usuallyfuses with the upper thoracic to lie on the neck of thefirst rib as the stellate ganglion.

Postganglionic grey rami communicantes leave theganglia to join the cervical spinal nerves. Other post-ganglionic branches pass to nearby arteries to be dis-tributed with them. The carotid nerve leaves the supe-rior ganglion to form a plexus on the internal carotidartery. Cardiac branches arise from the cervical sym-pathetic trunks and descend to supply the heart.

The phrenic nerve (C3,4,5, motor to thediaphragm) passes vertically downward on scalenusanterior, deep to the prevertebral fascia, and slightlylateral to the carotid sheath. Both phrenics pass poste-rior to the brachiocephalic or subclavian veins. Theright stays to the right of the right brachiocephalicvein to run on the superior vena cava. The left phrenicnerve (19) stays lateral to the vagus, the carotid arteryand then the aortic arch.

60 Head and Neck

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1 Clavicle2 Manubrium3 First rib4 Lateral lobe of thyroid gland5 Sternocleidomastoid6 External jugular vein7 Subclavian vein8 External carotid artery9 Internal carotid artery

10 Superior thyroid artery and vein

11 Suprascapular and transversecervical veins entering thesubclavian vein (a normalvariation)

12 Internal jugular vein13 Common carotid artery14 Subclavian artery15 Scalenus anterior16 Vagus nerve

17 Sympathetic trunk and cardiacbranches

18 Prevertebral muscles (longuscolli, longus capitis)

19 Left phrenic nerve20 Subclavius21 Upper trunk of brachial plexus22 Thyrocervical trunk23 Vertebral artery24 Splenius capitis

25 Trapezius26 Pectoralis major27 Pectoralis minor28 Scalenus medius29 Disc of sternoclavicular joint30 Sternal notch31 Body of sternum32 Deltoid

A Neck, deep dissection (from the left and slightlybelow)

B Neck, deep dissection with pharynx and larynxremoved (from the front and left)

Deep anterolateral neck, veins, nerves 61

Location of numbers: 1AB; 2A; 3A; 4A; 5A; 6A; 7AB; 8B; 9B; 10AB; 11A; 12A; 13AB; 14A; 15B; 16AB; 17B; 18B; 19B; 20B; 21B; 22B; 23B; 24B; 25B; 26B;27B; 28B; 29B; 30B; 31B; 32B.


The Thorax

Part IV

26 Mediastinum, from left 6427 Mediastinum, from right 6628 Thorax: thymus, pleural cavities,

thoracic skeleton, intercostal muscles 6829 Diaphragm 7030 Lungs: lobes, fissures, bronchi, hila,

relations 7231 Heart: in situ and removed 7432 Heart: chambers 7633 Heart valves and conducting system 7834 Heart: superior and external views,

major vessels, coronary arteries and veins 80

35 The breast, and the thoracic wall in respiration 82

Mediastinum, from left

The organs lying centrally in the thorax comprise themediastinum, which is divided into four parts:superior, anterior, middle and posterior. The latterthree may be grouped as the inferior mediastinum.

Contents

● Superior – great vessels, trachea and oesophagus● Anterior – thymus and internal thoracic vessels● Middle – heart and pericardium with the vagus and

phrenic nerves● Posterior – descending aorta, oesophagus, azygos

veins and thoracic ductThe thoracic vertebrae and ribs lie posterior to themediastinum. The manubrium, sternum and thecostal cartilages (2) lie anteriorly. The manubrioster-nal joint is a symphysis of fibrocartilage; it lies oppo-site T4–T5 and is palpable as the sternal angle ofLouis. The superior mediastinum is above T4–5 andbehind the manubrium.

The pericardium (3) on the left covers the left ven-tricle (4), and on the right, the right atrium. Each lunghilum (5–8) is a mirror image of the medial surface ofthe equivalent lung.

The internal thoracic (mammary) artery (9) sendsanterior intercostal arteries into each intercostal space,and is an important blood supply to the breast. Itdivides into the musculophrenic artery, which sup-plies the diaphragm, and the superior epigastric artery,which supplies the muscles of the anterior abdominalwall. The internal thoracic may be surgically re-routed toaugment or replace occluded coronary arteries. The anas-tomosis between the superior and inferior epigastricsmay open as a collateral circulation.

The thymus lies anteriorly in the mediastinum. Inthe adult it is largely replaced by fat. But it is impor-tant during childhood as a producer of T-lymphocytes,which have immunological function but have beenprogrammed to recognize and not destroy ‘self’.

The ascending aorta gives the left and right coronaryarteries, then ascends to the right of the trachea, tobecome the arch of the aorta at T4–5. The aortic arch(10) lies opposite T3 and T4, and has three branches:

the brachiocephalic trunk, the left common carotid(11) and the left subclavian (12) arteries. Thedescending aorta (15) continues from the arch atT4/5, and gives bronchial, oesophageal and posteriorintercostal (16) branches. The latter anastomose withthe anterior intercostals. The descending aorta lies onthe vertebral column, just to the left of the midline,but then moves to the midline to pass behind thediaphragm at T12.

The phrenic and vagus nerves on each side enter thethorax between the subclavian vein and subclavianartery, the vagus being more medial. The courses arethen asymmetrical. The left phrenic nerve (18) passesinferiorly, on the pericardium of the left ventricle,before passing through the central tendon of thediaphragm. Both phrenics give motor supply to thediaphragm, as well as sensory supply to the peri-cardium, mediastinal and diaphragmatic pleura, andperitoneum underlying the diaphragm.

The left vagus (19) runs with the left commoncarotid to reach the arch of the aorta, which it crossesbefore giving the recurrent laryngeal nerve (RLN). Theleft RLN is at risk of compression by tumours andaneurysms at the left lung hilum. The left vagus passesposteriorly, the left phrenic stays anterior, thereforethe two nerves cross each other on the aortic arch withthe left superior intercostal vein (20) between them.Both vagi pass posterior to the lung hilum. They sup-ply the pulmonary plexuses (bronchoconstriction) andthen combine to form an oesophageal plexus, whichcoalesces to pass through the diaphragm (with theoesophagus) as the anterior (mainly left) and posterior(mainly right) vagal trunks.

The thoracic duct, the main lymph trunk of thebody, is the continuation of the abdominal cisternachyli, and carries lymph from the whole body exceptthe right thorax, right upper limb and right half of thehead and neck. It passes behind the diaphragm withthe aorta and azygos vein. Aortic pulsation promotesthe return flow of both lymph and venous blood. Theduct ascends in the midline, or just to the right, untilT5, where it crosses to the left, behind the oesopha-gus. It passes upward in the superior mediastinum andthen arches over the apex of the left lung and pleurato enter the formation of the left brachiocephalic vein.

64 The Thorax

1 First rib2 Second costal cartilage3 Pericardium4 Left ventricle5 Left pulmonary artery6 Left superior pulmonary vein

(divided)7 Left inferior pulmonary vein

8 Left main bronchus9 Internal thoracic (mammary)

artery and vein10 Arch of aorta11 Left common carotid artery12 Left subclavian artery13 Left subclavian vein14 Left brachiocephalic vein

15 Descending thoracic aorta16 Posterior intercostal artery, vein

and nerve17 Sixth rib18 Left phrenic nerve19 Left vagus nerve20 Left superior intercostal vein21 Sympathetic trunk and ganglion

22 Cervicothoracic (stellate)ganglion

23 Greater splanchnic nerve24 Oesophagus25 Clavicle

A Left lung root and mediastinum (from the left)

Mediastinum, from left 65

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Mediastinum, from right

The trachea (11) is visible from the right but is over-laid by the aortic arch on the left. It divides into theleft and right main bronchi at T4/5, in the concavity ofthe arch of the aorta, adjacent to the bifurcation of thepulmonary artery (trunk). The right vagus nerve (12)lies on it.

The superior vena cava (13), formed behind the firstcostal cartilage by the fusion of the right (14) and left(15) brachiocephalic veins, enters the right atriumopposite the third costal cartilage. The inferior venacava (IVC) pierces the diaphragm and immediatelyenters the right atrium. The right phrenic nerve (16)lies immediately lateral to the right brachiocephalicvein, superior vena cava and pericardium of the rightatrium. It passes through the diaphragm with the IVCat the level of T8.

The azygos vein (17) commences in the abdomenand passes behind the diaphragm to enter the thorax.The posterior intercostal veins drain into the azygossystem, which also receives bronchial and oesophagealveins. The azygos lies on the vertebral column beforepassing superior to the right lung hilum to enter thesuperior vena cava. On the left, upper and lowerhemiazygos veins cross the midline to enter theazygos.

Sympathetic innervation

Primary preganglionic sympathetic nerves emergefrom the cord in the ventral roots of T1–L2 spinalnerves, but leave as white rami communicantes toenter the sympathetic trunk, where they usuallysynapse. The sympathetic trunk (18) lies parallel tothe vertebral column, from atlas to coccyx and distrib-utes sympathetic innervation throughout the body.The trunk is studded with ganglia, clusters of cell bod-ies of the secondary, postganglionic sympatheticnerves.

White rami enter the trunk and synapse in adjacentganglia or pass up or down the trunk to synapse in dis-tant ganglia. Wherever the synapse, the secondarypostganglionic sympathetic nerves leave the trunkeither as the grey rami communicantes that join all thespinal nerves or they join blood vessels to be distrib-

uted accordingly. The stellate ganglion (20) of thesympathetic trunk lies on the neck of the first rib as itpasses into the neck. Tumours at the lung apex maycompress the trunk and interrupt sympathetic supply tothat side of the head – Horner’s syndrome (constrictedpupil (myosis), drooping eyelid (ptosis), dry face).

Splanchnic nerves to the intestinal tract are anexception. The primary preganglionic sympatheticnerves pass through the trunk without synapsing. Thegreater splanchnic (21), the lesser, and the leastsplanchnic nerves leave their origins in the T5–9,T10–11 and T12 segments of the cord, respectively.Having branched from the appropriate spinal nervesto enter the sympathetic trunks, they leave the trunksand pass into the abdomen. They synapse in ganglia onthe aorta, associated with, and distributed with, thearteries to the intestine. These nerves also contain affer-ent fibres that are important when considering referredpain in the abdomen. The nerves are surgically divided inpatients with chronic pain (e.g. chronic pancreatitis).

The oesophagus (22) transports food and fluid fromthe pharynx to the stomach. It commences at C6 andlies in the midline, immediately anterior to the verte-bral column but deep to the trachea and then the leftatrium. Inferiorly it lies to the right of the descendingaorta, but passes anterior to the aorta (itself moving tothe midline) to pierce the diaphragm just to the left ofthe midline (but through the right crus) at T10, andalmost immediately enters the stomach.

The oesophagus is supplied by the recurrent laryn-geal and vagus nerves. Arteries are from the inferiorthyroid, and the aorta, except the lower end, which issupplied by the left gastric artery. The veins form arich submucosal anastomosis that drains to the azygossystem, or to the portal system via the left gastric vein.Therefore, the oesophagus is an important site ofportosystemic venous anastomosis. Lymphatic drainagefollows the arteries.

Cricopharyngeus forms a sphincter at the upper endof the oesophagus and only opens during swallowingor vomiting. Occasionally the sphincter does not openquickly enough during vomiting, causing pressure torise within the oesophagus and tear the mucous mem-brane. The resultant blood is visible in the vomit (hae-matemesis).

66 The Thorax

1 Pericardium over right atrium2 Internal thoracic (mammary)

artery and vein3 Third costal cartilage4 Right subclavian vein5 Right subclavian artery6 Right pulmonary artery (divided)7 Superior right pulmonary vein

(divided)

8 Inferior right pulmonary vein(divided)

9 Right main bronchus (divided)10 Ascending aorta covered by

pericardium11 Trachea12 Right vagus nerve13 Superior vena cava14 Right brachiocephalic vein

15 Left brachiocephalic vein16 Right phrenic nerve17 Azygos vein18 Sympathetic trunk and ganglion19 Posterior intercostal artery, vein

and nerve20 Cervicothoracic (stellate)

ganglion21 Greater splanchnic nerve

22 Oesophagus23 First rib24 Clavicle25 Diaphragm

A Right lung root and mediastinum (from the right)

Mediastinum, from right 67

A

3

110

13 16

15

2

14234

5

24

19

18

21

98

7

611

2022

12

17

25

A

IS

P

Thorax: thymus, pleural cavities,thoracic skeleton, intercostalmuscles

Pleural cavities

On each side the thoracic cavity appears as if filledwith a ‘balloon’ of serous membrane, the pleura. Theparietal layer covers the mediastinum, costal carti-lages, ribs and diaphragm. It extends up to the neck ofthe first rib and down into the costodiaphragmaticrecess where the diaphragm attaches inferiorly to thetwelfth rib. Each lung invaginates the pleura from itsmedial side. Therefore, the visceral layer covers thelung and at the hilum (where the vessels and nervesenter and leave) it reflects to become the parietallayer. The visceral pleura dips into the fissuresbetween the lung lobes. The pleural cavity, betweenthe visceral and parietal layers, is a potential spacewith a minuscule amount of lubricating pleural fluid.

Surface markings

The pleural reflections are mapped on to the thoracicwall in relation to the ribs. The apex is about 2 cmabove the medial one-third of the clavicle (2). Thepleural cavities lie beside each other in the midline atthe level of the second costal cartilage. They continueinferiorly in the midline, but the left deviates to theleft at the level of the fourth costal cartilage to makeway for the heart, whereas the right cavity continuesto the sixth costal cartilage. Laterally, they extend fur-ther to reach the eight rib in the midclavicular line,tenth rib in the midaxillary line and twelfth rib poste-riorly. The inferior edges of the lungs are two ribspaces higher: the sixth rib in the midclavicular line,eighth rib in the midaxillary line and tenth rib posteri-orly.

Ribs, costal cartilages

With the exception of the first, eleventh and twelfthribs, the head of each rib (3) articulates with its ownvertebra, the one above, and the disc between. Thetubercle (4) articulates with the transverse process ofits own vertebra. Consequently, the neck (5) of eachrib slopes downward and laterally. Rib movement islargely by rotation around the axis of that downward-sloping rib neck.

The shaft (6) of each rib also slopes downward as itcurves around the chest. The hyaline costal cartilage(7) passes from the end of the rib to the sternum, orto the costal cartilage above, forming the costal mar-gin. The first four costal cartilages are short and hori-zontal; the others are longer and slope upward. Thefirst rib has a horizontal neck. The eleventh andtwelfth ribs have horizontal necks and do not articu-late with the sternum or costal margin.

Intercostal muscles

Muscles form three layers within the intercostalspaces. The external intercostal muscle passes down-ward and forward from one rib to the next, becomingthe external intercostal membrane between the costalcartilages. The internal intercostal muscle (8) passesdownward and backward from one costal cartilage andrib to the next. It becomes the internal intercostalmembrane posteriorly. The innermost layer is incom-plete but present anteriorly as transversus thoracis andposteriorly as subcostalis. These innermost musclescross more than one intercostal space.

The intercostal neurovascular bundle (vein, artery,nerve) lies in the groove inferior to each rib. Their col-lateral branches runs along the upper border of the ribbelow. They supply the intercostal muscles, overlyingskin and underlying parietal pleura.

Pleural effusion is a collection of excess pleural fluid.Rupture of lung tissue, or of the overlying chest wall, mayallow air to enter the pleural cavity (pneumothorax).Associated bleeding will cause a haemopneumothorax.Such collections of air or blood in the pleural cavity areremoved by inserting a chest drain into the fifth intercostalspace, mid-axillary line. The skin is anaesthetized andincised, and then blunt dissection is used to pass throughthe intercostal muscles and avoid damage to the neu-rovascular bundles.

If air enters into the pleural cavity continually, with noroute of escape, pressure builds within the cavity to col-lapse the lung. This is a tension pneumothorax, and thepressure may be high enough to push the heart and tra-chea off the midline, severely embarrassing respirationand venous return to the heart. The situation is potentiallylife-threatening, and the pressure must be relievedurgently by a needle in the second intercostal space, mid-clavicular line.

68 The Thorax

A B

C D

26 210

918

19

22

21

2016

13

14

167

6 1

11

12

17

2

23

2710

13

15

2

17

2931

35

10

11

13

1432

33 30

34

3

5

4

6

28

24825

9

S

LR

I

S

LR

I

S

LR

I

P

Lat(L)

M

A

1 Internal thoracic (mammary)artery and vein

2 Clavicle3 Head of rib4 Tubercle of rib5 Neck of rib6 Body (shaft) of rib7 Costal cartilage8 Internal intercostal muscle9 Sternoclavicular joint

10 Jugular (suprasternal) notch11 Manubrium of sternum12 Manubriosternal joint (angle of

Louis)13 Body of sternum14 Xiphoid process15 Serratus anterior16 Pleura over lung17 First rib18 Second rib

19 Third rib20 Fourth rib21 Fifth rib22 Sixth rib23 Clavicular part of pectoralis

major24 Sternocostal part of pectoralis

major25 Pectoralis minor26 Deltoid

27 Sternocleidomastoid28 Rectus abdominis29 Superior lobe of left lung30 Inferior lobe of left lung31 Superior lobe of right lung32 Middle lobe of right lung33 Inferior lobe of right lung34 Oblique fissure of left lung35 Transverse fissure of right lung

A Muscles of the thoracic wall (from the front)B Thoracic cavity with ribs, pleural covering and lungs in

situ (from the front)C Thoracic cavity with ribs and lungs in situ (from the

front)D A left typical rib (from above)

Thorax: thymus, pleural cavities, thoracic skeleton, intercostal muscles 69

Location of numbers: 1B; 2ABC; 3D; 4D; 5D; 6BD; 7B; 8A; 9AB; 10ABC; 11BC; 12B; 13ABC; 14BC; 15A; 16B; 17BC; 18B; 19B; 20B; 21B; 22B; 23A; 24A;25A; 26A; 27A; 28A; 29C; 30C; 31C; 32C; 33C; 34C; 35C.

Diaphragm

The diaphragm is the primary muscle of inspiration. Itarises from the vertebral column, arcuate ligaments,ribs and sternum to form left (1) and right (2) muscu-lar domes that ascend into the thorax and insert intothe central tendon (3) of the diaphragm. The nervesupply to each half is by the left and right phrenic(C3,4,5), respectively.● Diaphragmatic crura – posteriorly a right muscular

crus (4) arises from the first three lumbar vertebrae,and a left crus (5) from the first two. The crura bothascend to the central tendon, but the right crusmoves to the left to sweep around the loweroesophagus (6) and contribute to its physiologicalcardiac sphincter.

● Arcuate ligaments – the median arcuate ligamentlies at T12 between the two crura. The medial arcu-ate ligament is formed from the fascia over psoasmajor (7) and passes from the body to the trans-verse process of L1. The lateral arcuate ligament isformed from the fascia over quadratus lumborum(8) and runs from the transverse process of L1 tothe tip of the twelfth rib. Muscular fibres ascendfrom the arcuate ligaments to the central tendon.Should the fibres that arise from the medial or lateralligaments be absent at birth, the abdominal contentswill move into the thorax – congenital diaphragmatichernia (hernias of Bochdalek and Morgagni).

The remaining diaphragm muscle arises from the inneraspects of the lower six ribs and costal cartilages (inter-digitating with transversus abdominis) around to thexiphisternum, which also sends muscle fibres to thecentral tendon.

Structures passing through (or behind) thediaphragm

The aorta (9), thoracic duct (10) and azygos vein (11)pass behind the median arcuate ligament. The oesoph-agus and the two vagal trunks pass through the rightcrus, just to the left of the midline at T10.

The splanchnic nerves pierce the crura on their wayto the coeliac plexus, which forms around the coeliac

trunk (12). The coeliac trunk arises from the aortabetween the crura. The sympathetic chain passesbehind the medial arcuate ligament, and the subcostalneurovascular bundle behind the lateral.

The inferior vena cava (13) and right phrenic nervepass through the central tendon at T8, i.e. behind theright sixth costal cartilage, just to the right of the mid-line. The left phrenic nerve sends its branches throughthe left diaphragmatic dome.

Relations

The underlying abdominal relations differ on each sideand may be in danger during the insertion of a chestdrain or following rib fracture. The liver (14) is on theright, the stomach (16) and spleen (18) on the left.On each side, the kidney (19,20) lies posteriorly in theabdomen, partially on the diaphragm and thereforerelated to the costodiaphragmatic recess (21).

Diaphragmatic movements

On inspiration the domes flatten to increase the verti-cal thoracic diameter. With increased respiratoryeffort the central tendon descends too. But its descentis limited by its attachment to the pericardium (22)and by the underlying abdominal viscera. Furtherdiaphragmatic contraction, in forced inspiration, pullson the ribs and costal cartilages to evert the seventh totenth ribs. This ‘bucket handle’ movement increasesthe lateral thoracic diameter.

Expiration is by relaxation, elastic recoil and by pres-sure from the underlying abdominal viscera. The lattermay be increased by contraction of the abdominal wallmuscles.

The pleura superior to the diaphragm, and the peri-toneum inferior to it, both have sensory supply by thephrenic nerve (C3,4,5). Irritation of the undersurface ofthe diaphragm (cholecystitis, blood from a rupturedspleen) may refer pain to the respective shoulder tip, sup-plied by C3,4 via the lateral supraclavicular nerve.

Paralysis of one side of the diaphragm will result in par-adoxical movement. During inspiration the paralysed sideis forced upward (instead of the expected downwardmovement) by the raised intra-abdominal pressure that iscreated by descent of the healthy half of the diaphragm.

70 The Thorax

1 Left dome of diaphragm2 Right dome of diaphragm3 Central tendon of diaphragm4 Right crus of diaphragm5 Left crus of diaphragm6 Oesophagus7 Psoas major8 Quadratus lumborum

9 Aorta10 Thoracic duct11 Azygos vein12 Coeliac trunk13 Inferior vena cava14 Right lobe of liver15 Gall bladder16 Fundus of stomach

17 Left lobe of liver18 Spleen19 Left kidney20 Right kidney21 Costodiaphragmatic recess22 Fibrous pericardium23 Lower lobe left lung24 Right atrium

25 Hemi-azygos vein26 Left greater splanchnic nerve27 Body (lower end) of sternum28 Falciform ligament29 Inferior phrenic vessels

A Diaphragm (from above)B Diaphragm (from below)C Upper abdomen, contents (from the front)

Diaphragm 71

A B

C

27

3

2916

197

8

20

17

14

15

16

6 23

21

18

1920

139

41229 6

5

1

22

9

6

13

243

2

11

26 25

10

28

S

LR

I

A

RL

P

A

LR

P

Location of numbers: 1A; 2A; 3AB; 4B; 5B; 6ABC; 7B; 8B; 9AB; 10A; 11A; 12B; 13AB; 14C; 15C; 16BC; 17C; 18C; 19BC; 20BC; 21C; 22A; 23C; 24A;25A; 26A; 27A; 28C; 29B.

Lungs: lobes, fissures, bronchi,hila, relations

The lungs are for respiration, the exchange of oxygenand carbon dioxide between the blood and the atmos-phere. Respiration ensures oxygenation of the bloodand also maintains its correct pH.

Lung surface projections are the same as the pleura,except inferiorly where they are two rib spaces higher(p. 68). On full or forced inspiration the lungs descendinto the costodiaphragmatic recesses.

Lobes and fissures

Both lungs are divided into an upper and a lower lobeby the oblique fissure (1). The transverse fissure (2)further subdivides the right upper lobe. So the leftlung has two lobes (3,4) and the right lung three lobes(5,6,7). Surface projection of each oblique fissure is tothe spines of T3/T4 (palpable on examination) or thebody of T5 (visible on a radiograph) and then aroundthe chest to the sixth rib. The transverse fissure is deepto the right fourth costal cartilage and rib, meeting theoblique fissure at the fifth rib. Surface projection ofthe fissures allows approximate location of the lunglobes and segments during examination of the thorax.Essentially, the upper lobe is anterior, the lower lobe pos-terior, and the middle lobe lateral.

Bronchi and bronchopulmonary segments

The trachea and bronchi are fibro-elastic tubes, heldopen by cartilage, but with muscle in their walls tocontrol diameter. The muscle contracts underparasympathetic stimulation in quiet respiration,reducing the dead space. The muscle relaxes, undersympathetic control, to allow increased airflow asrespiratory demand rises. Asthma is the excessiveconstriction of the bronchioles. One therapy uses drugsthat have a sympathetic effect of dilating the bronchi.

The right main bronchus (8) is shorter, wider andmore vertical than the left, therefore more likely to receiveforeign bodies. The left lung is displaced to the left bythe heart, so looks longer and narrower than the rightlung, but this also means that the left bronchus (9) islonger and more horizontal.

Within the lung, or just outside it, the bronchidivide into lobar (secondary bronchi) and then bron-

chopulmonary segments (tertiary bronchi). These seg-ments may be surgically removed or be the location of apneumonia. Each upper lobe has an apical, an anteriorand a posterior segment. Each lower lobe has an apicalsegment and four basal segments, medial, lateral, ante-rior and posterior. The middle lobe (6) on the righthas medial and lateral segments. The lingula (10) isthe equivalent on the left, with upper and lowersegments. On each side, there are ten segments in all,but the heart causes some on the left to be small.

The first tertiary bronchus to arise from the bronchialtree posteriorly is to the apical segment of the lower lobe(11), which is therefore prone to pneumonia. It lies highin the thorax adjacent to the T4 spine.

The hilum contains lymph nodes, and bronchialarteries and veins to supply the bronchi and lung tis-sue. The bronchial arteries arise from the aorta or pos-terior intercostal arteries. The bronchial veins drain tothe azygos system. Each hilum receives air via itsbronchus, and de-oxygenated blood via its pulmonaryartery. The left bronchus and the left pulmonaryartery (12) are single. But the right bronchus and theright pulmonary artery (13) bifurcate just before thehilum so the right hilum has two bronchi and twoarteries. Both hila have two main (superior (14) andinferior (15)) pulmonary veins to carry oxygenatedblood back to the left atrium. The bronchi tend to beposterior, the pulmonary arteries anterosuperior, andthe pulmonary veins antero-inferior.

Lymph drainage

The lung is drained by plexuses of lymph vessels thatlie on the bronchi and under the pleura. They con-verge on the hilar lymph nodes (16), which send affer-ents to the tracheobronchial nodes and then to themediastinal nodes. Lung tumour may spread to thesenodes and be seen on radiographs as a slight widening ofthe mediastinum.

Relations

Apart from the phrenic and vagus nerves, the medi-astinal relations are different for each lung. The left isrelated to the left ventricle, aortic arch, descendingaorta and oesophagus inferiorly. The right lung isrelated to the superior vena cava, trachea, azygos veinand right atrium.

72 The Thorax

1 Oblique fissure2 Transverse fissure3 Superior lobe of left lung4 Inferior lobe of left lung

5 Superior lobe of right lung6 Middle lobe of right lung7 Inferior lobe of right lung8 Right main bronchus (divided)

9 Left main bronchus10 Lingula of left lung11 Apical segment of lower lobe12 Left pulmonary artery

13 Right pulmonary artery (divided)14 Superior pulmonary veins (divided)15 Inferior pulmonary veins16 Hilar lymph nodes

A Left lung, medial aspect (from the right)B Left lung, lateral aspect (from the left)C Right lung, medial aspect (from the left)D Right lung, lateral aspect (from the right)

Lungs: lobes, fissures, bronchi, hila, relations 73

A B

C

D

1

11

15

9

12 11

1

5

11

11 1

5

2

6

7

138

14

1415

7

6

16

4

10

14

16

3

3

4

10

S

AP

I

S

PA

I

S

AP

I

S

PA

I

Location of numbers: 1ABD; 2D; 3AB; 4AB; 5CD; 6CD; 7CD; 8C; 9A; 10AB; 11ABCD; 12A; 13C; 14AC; 15AC; 16AC.

Heart: in situ and removed

The heart lies centrally within the thorax and is themuscular pump that receives, on its right side, de-oxy-genated blood, which is pumped to the lungs for oxy-genation. The oxygenated blood returns from thelungs to the left side of the heart to be pumped intothe systemic circulation. Consequently, there are rightand left receiving chambers, the atria, and right andleft pumping chambers, the ventricles.

Pericardium

The heart is enclosed in the pericardial sac (1) in themiddle mediastinum. The external layer of fibrouspericardium is lined by serous parietal pericardium.Where the major vessels pierce the pericardium toenter or leave the heart, the parietal layer reflects ontothe vessels and continues around the heart as the vis-ceral pericardium (epicardium). The resultant, lubri-cated potential space between the parietal and viscerallayers allows cardiac movement and contraction.

Within the pericardial sac, between the visceral andparietal layers there are the oblique and transversesinuses. The former is a potential space behind the leftatrium (2) to allow its expansion. The latter has theascending aorta (3) and pulmonary trunk (4) anteri-orly, the superior vena cava (5) and the upper aspectof the left atrium posteriorly. During cardiac surgeryslings and clamps are passed through the transverse sinusto control blood flow in the great vessels.

The fibrous pericardium fuses with the great vesselssuperiorly and the central tendon of the diaphragm(10) inferiorly. This latter attachment limits thedescent of the central tendon.

Nerve supply and referred pain

The fibrous and parietal pericardia both receive sensa-tion via the phrenic nerves. The visceral pericardium,

like the heart itself, receives sensation via the sympa-thetics. Although the cardiac branches descend intothe thorax from the cervical parts of the sympathetictrunks, their origin in the spinal cord is from T1–5segments. Therefore pain from the heart and visceralpericardium usually refers to the anterior chest wall.But it may also extend into the T1 and T2 dermatomesdown the inner aspect of the left arm. Blood and fluidmay collect within the pericardial sac, which can reducevenous return and cardiac contraction – cardiac tampon-ade.

The heart lies behind the sternum but extends to theleft. In the sagittal plane it lies obliquely so that theapex (12) is anterior and the base posterior. The rightborder is the right atrium (13). The anterior (ster-nocostal) surface is mainly right ventricle (14). Theleft border and apex is left ventricle. The inferiorsurface lies on the diaphragm and is formed mainly byleft ventricle and partially right ventricle. The base,which is left atrium, lies posteriorly, related to theoesophagus and descending aorta opposite T5–7.

Surface projections of the four corners of theheart (Illustration B)

● Upper left – at the left second costal cartilage,parasternally (P)

● Upper right – at the right third costal cartilageparasternally (A)

● Lower right – at the right sixth costal cartilage,parasternally (or T8 where the inferior vena cavapierces the diaphragm and immediately enters theright atrium) (T)

● Lower left – or apex (palpable) at the left fifth inter-costal space, mid-clavicular line (M)

74 The Thorax

1 Pericardium2 Left atrium3 Ascending aorta4 Pulmonary artery (trunk)5 Superior vena cava6 Left superior pulmonary vein7 Left inferior pulmonary vein8 Left auricle

9 Left ventricle10 Central tendon of diaphragm11 Right auricle12 Apex of heart13 Right atrium14 Right ventricle15 Left pulmonary artery16 Left and right main bronchi

17 Right pulmonary artery (divided)18 Right superior pulmonary vein19 Right inferior pulmonary vein20 Inferior vena cava21 Coronary sinus in atrioventricular

(coronary) groove22 Left brachiocephalic vein23 Right brachiocephalic vein

24 Trachea25 Arch of aorta26 Brachiocephalic trunk27 Left common carotid artery28 Internal thoracic (mammary)

artery29 Azygos vein

A Thorax with ribcage removed (from the front)B Ribs and heart, surface markings (from the front)C Heart (from the front)D Heart (from behind)

Heart: in situ and removed 75

B

C D

A

2326

27

24

2225

2828

1

10

3

67

43

22

23

5

13

11

14 12

16

15 16 29

17 5

18

19

2

6

7

12

14

20 13

21

9

8

S

LR

I

S

RL

I

S

LR

I

S

LR

I

Location of numbers: 1A; 2D; 3C; 4C; 5CD 6CD; 7CD; 8C; 9C; 10A; 11C; 12CD; 13CD; 14CD; 15D; 16D; 17D; 18D; 19D; 20D; 21D; 22AC; 23AC; 24A;25A; 26A; 27A; 28A; 29D.

Surface projections of the four corners of the heart

P

MT

A

Heart: chambers

During the cardiac cycle blood is ejected from the ven-tricles by their contraction during systole. During dias-tole the ventricles relax and are filled with blood byatrial contraction. The atrioventricular valves ensureunidirectional flow from atrium to ventricle.

The interventricular septum (1) separates the left(2) and right (3) ventricles. On the surface, that sep-aration is visible anteriorly and posteriorly as the inter-ventricular groove (4). Similarly, on both surfaces theatrioventricular groove, between the two atria and thetwo ventricles, is visible and represents the position ofthe figure-of-eight fibrous skeleton that separates theatria from the ventricles. The fibrous skeleton liesobliquely, just off the coronal plane. It houses theatrioventricular valves and it breaks the wave of con-duction from the atria to the ventricles. Congenital andpathologically acquired defects can occur in the interven-tricular septum allowing the shunting of blood from theleft to the right side of the heart (ventricular septal defector VSD).

The interatrial septum (5) separates the right atriumfrom the left atrium. As the right atrium is actuallyanterior to the left, the septum forms the posteriorwall of the right atrium. Both atria develop from orig-inal fetal atrium, and also from the incorporation oforiginal fetal vein. The auricles, ridged by musculipectinati are the remnants of fetal atrium, whereas thesmooth part of each atrium represents fetal vein. Theright atrium (6) receives both the superior (7) andinferior vena cavae (8) and the coronary sinus (9).The crista terminalis (10) is an internal ridge running

longitudinally between the vena cavae. Musculi pecti-nati (11) run from the crista terminalis into theauricle (12).

The interatrial septum, lying posteriorly, shows thefossa ovalis (13), which indicates the position of thefetal foramen ovale. In the fetus, blood bypasses thepulmonary circulation by flowing through the foramenovale from right to left atrium. The foramen closes atbirth, but many people have asymptomatic ‘probepatency’. That is, after death, a probe may be passedthrough a residual aperture in the interatrial septum.

During diastole blood passes through the tricuspidvalve (14) into the right ventricle, which appears cres-cent-shaped and wraps around the thicker, circular leftventricle. The right ventricle has muscular ridges, tra-beculae carneae (20) that smooth out and disappeartowards the infundibulum, which leads to the pul-monary trunk.

The atrial and ventricular muscular ridges givepower of contraction, without taking up space or mak-ing the heart walls excessively thick. Their disappear-ance and return to a smooth surface ensures laminarblood flow.

The left atrium (21) is quadrangular and on the baseof the heart, posteriorly. It has an auricle but is mainlysmooth and receives oxygenated blood via the left(27) and right (28) superior and inferior pulmonaryveins. During diastole blood passes through the bicus-pid mitral valve to the left ventricle. The left ventriclehas numerous fine trabeculae carneae, which decreasetowards the aortic vestibule, to ensure laminar flow.

In both ventricles there are papillary muscles associ-ated with valve function.

76 The Thorax

1 Muscular part of interventricularseptum

2 Left ventricle3 Right ventricle4 Position of interventricular

groove (posteriorly)5 Interatrial septum6 Right atrium7 Superior vena cava8 Inferior vena cava9 Coronary sinus

10 Crista terminalis11 Musculi pectinati12 Right auricle13 Fossa ovalis14 Tricuspid valve15 Posterior cusp of tricuspid

valve16 Septal cusp of tricuspid valve17 Anterior cusp of tricuspid valve18 Right ventricular wall19 Left ventricular wall

20 Trabeculae carneae in rightventricle

21 Left atrium22 Right pulmonary artery23 Position of atrioventricular node24 Limbus fossa ovalis25 Position of intravenous tubercle

of interatrial septum26 Ascending aorta27 Left pulmonary veins28 Right pulmonary veins

29 Marginal branch of rightcoronary artery

30 Septal papillary muscle31 Anterior interventricular

(descending) branch of leftcoronary artery ininterventricular groove

32 Great cardiac vein33 Apex of heart

A Open right atrium (from the front and right)B Axial section through the ventricles (from below)C Heart (from behind)

Heart: chambers 77

A B

C

11

11 10

7

12

722

28

8

6

18433

19

9

27

21

26

12

18

29

17 320

1 2

19

32

31

306

5

25

1324

23

1614

17

15

18

4

19921

2822

S

LR

I

S

RL

I

A

LR

P

Location of numbers: 1B; 2B; 3B; 4AC; 5A; 6AC; 7AC; 8C; 9AC; 10A; 11A; 12AB; 13A; 14A; 15A; 16A; 17AB; 18ABC; 19ABC; 20B; 21AC; 22AC; 23A;24A; 25A; 26B; 27C; 28AC; 29B; 30B; 31B; 32B; 33C.

Heart valves and conductingsystem

The atrioventricular valves are both opened and closedby the pressure of blood. Flow of blood during atrialcontraction (diastole) pushes the cusps into the ventri-cle. During ventricular contraction (systole) the bloodpressure pushes the valves shut and the papillary mus-cles and chordae tendineae prevent the cusps fromeverting into the atrium.

The tricuspid valve (1) has posterior (or inferior)(2), septal (3) and anterior (4) cusps. There arerespective papillary muscles (5,6), but each of thesesends chordae tendineae (7) to two cusps.Consequently, the cusps are drawn together as well asbeing held shut.

The mitral valve has two cusps, the anterior (8) andposterior (9) cusps. There are equivalent papillarymuscles (10,11), although each sends chordaetendineae to both cusps. The anterior cusp is smoothon both surfaces as it lies between the ventricularinflow and its outflow, the aortic vestibule.

Auscultation

The atrioventricular and arterial valves lie in a line –pulmonary, aortic, mitral and tricuspid – behind thesternum. On auscultation their sounds are best heardby following the direction in which blood flows as itpasses through each valve:● Tricuspid – sixth right interspace or at the lower

end of the sternum● Mitral – at cardiac apex, left fifth interspace, mid-

clavicular line● Aortic – right second intercostal space● Pulmonary – left second intercostal spaceThe valves may be diseased and become narrowed(stenosed) or leak (incompetent). Additional abnormalmurmurs are heard on auscultation during the cardiaccycle.

The cardiac conducting system

The heart must beat continually and rhythmically.Heart rate is slowed by parasympathetic supply from

the cervical parts of the vagus nerves and their recur-rent laryngeal branches. Heart rate is raised by sympa-thetic supply that reaches the heart in branchesdescending from the cervical parts of the left and rightsympathetic trunks. The parasympathetic and sympa-thetic branches converge on superficial and deep car-diac plexuses that lie together at the ligamentumarteriosum and bifurcations of the pulmonary trunkand trachea. These three points are immediately adja-cent to each other. The plexuses send branches intothe heart with the coronary arteries. They also supplythe sinu-atrial node, or pacemaker of the heart.

The sinu-atrial node (24) lies at the upper end ofthe crista terminalis (25), which is just at the entry ofthe superior vena cave (26), where the auricle joinsthe atrium. Conduction and consequent contractionspread through the atria to propel blood toward andthrough the atrioventricular valves.

The conduction must not continue, unco-ordinated,straight into the ventricles. If it did so, the contractionmay be not only irregular but also in the wrong direc-tion, toward the inferior end of each ventricle.Consequently, the atrioventricular node (27), in theinferior aspect of the interatrial septum, ‘gathers’ theconduction and transmits it through the cardiacfibrous skeleton and into the bundle of His.

The bundle of His passes down the interventricularseptum (34), to divide into right and left bundles thatbranch out into each ventricle. The wave of conduc-tion and contraction is then synchronous, and fromthe lower aspect of each ventricle up toward its out-flow. In the right ventricle the moderator band (sep-tomarginal trabeculum) carries conduction from theright branch of the bundle of His to the base of theanterior papillary muscle. This ensures it is ready tocontract in synchrony with the other papillary muscles

Abnormalities of cardiac rhythm severely affect cardiacfunction. Excessive ventricular tachycardia or fibrillationrenders cardiac function as useless as if the heart hadstopped beating altogether. Both conditions can result incardiac arrest. The coronary arteries fill during diastole.Abnormal rhythm may prevent normal coronary arteryfilling and cause cardiac ischaemia.

78 The Thorax

1 Tricuspid valve2 Posterior cusp of tricuspid

valve3 Septal cusp of tricuspid valve4 Anterior cusp of tricuspid valve5 Anterior papillary muscle of right

ventricle6 Posterior papillary muscle of

right ventricle7 Chordae tendineae8 Anterior cusp of mitral valve9 Posterior cusp of mitral valve

10 Anterior papillary muscle of leftventricle

11 Posterior papillary muscle of leftventricle

12 Great cardiac vein13 Left coronary artery branches14 Musculi pectinati in left auricle15 Left auricle16 Ascending aorta17 Posterior cusp of aortic valve18 Left cusp of aortic valve19 Right cusp of aortic valve

20 Membranous part ofinterventricular septum

21 Right atrium22 Right auricle23 Musculi pectinati in right auricle24 Position of sinu-atrial node25 Crista terminalis26 Superior vena cava27 Position of atrioventricular node28 Right coronary artery in

atrioventricular groove29 Right ventricular wall

30 Trabeculae carneae in leftventricle

31 Left ventricle32 Left ventricular wall33 Left atrium34 Interventricular septum35 Right ventricle36 Right pulmonary veins37 Apex of heart38 Left pulmonary veins entering

left atrium

A Heart, coronal section – anterior portion (from behind)B Heart, coronal section – posterior portion (from the

front)C Opened right atrium (from the front and right)D Closed mitral valve (from behind)

Heart valves and conducting system 79

A B

C

D

9

8

S

RL

I

33

38

13

12

32

11

10

37

3130

34

6

22

23

2426

36

3332

29

231

27

21

25

4

29

357

228

21

3

25

26

36

16 18

2020

17 87

15

141312

3210

11

37

34

3131

305

29

35

428

23

2221

16

19

18

20

26

S

RL

I

S

LR

I

S

LR

I

Location of numbers: 1C; 2BC; 3BC; 4AC; 5A; 6B; 7B; 8BD; 9D; 10AB; 11AB; 12AB 13AB; 14A; 15A; 16AB; 17B; 18AB; 19A; 20AB; 21ABC; 22AC; 23AC;24C; 25BC; 26ABC; 27C; 28AB; 29ABC; 30AB; 31AB; 32ABC; 33BC; 34AB; 35AB; 36BC; 37AB; 38B.

Heart: superior and externalviews, major vessels, coronaryarteries and veins

Superior aspect of the heart

The superior vena cava (1), which carries de-oxy-genated blood from the head, neck, upper limbs andthoracic wall, enters the right atrium. The pulmonarytrunk (2) leaves the right ventricle and divides into theleft (3) and right (4) pulmonary arteries that carry de-oxygenated blood to each lung.

The aorta (5) leaves the left ventricle, ascends andthen arches backward over the pulmonary trunk andleft main bronchus (6), before becoming the descend-ing aorta at T4/5. It distributes oxygenated (arterial)blood to the systemic (body) circulation. As it emergesfrom the heart the aorta is slightly posterior and to theright of the pulmonary trunk, between it and the supe-rior vena cava.

The right (8) and left (9) auricles extend from theirrespective atria around the base of the aorta and pul-monary trunk.

Aortic and pulmonary valves

Blood is ejected from the ventricles by their contrac-tion during systole. The aorta and pulmonary trunk areelastic arteries and their elastic recoil during diastolepropels blood onward.

The pulmonary (14,15,16) and aortic (17,18,19)valves all have three semilunar cusps that are forcedoutward against the wall of each vessel during systole.Above each cusp there is a small dilation or sinus.During diastole, the elastic recoil not only forces bloodonward but also creates back pressure, which forcesblood into the sinuses between the cusps and the ves-sel wall. Therefore the cusps are forced to meet eachother in the middle of the arterial lumen to occlude itand prevent backflow into the ventricles.

Various diseases may cause the valves to become nar-rowed (stenosis), and/or allow leakage of blood back intothe ventricle during diastole (incompetent).

Cardiac blood supply

The coronary arteries arise from two of the sinuses inthe ascending aorta. The right coronary artery (20)

emerges from the sinus above the right cusp. It lies inthe atrioventricular groove and passes to the inferiorborder of the heart. It gives the marginal artery (21)before continuing on the postero-inferior surface, inthe atrioventricular groove, to give the posterior inter-ventricular artery (22) in the posterior interventricu-lar groove.

The left coronary artery (23) arises from the sinusabove the left cusp. It divides into the circumflexartery (24), which continues around the heart in theatrioventricular groove, and the anterior interventricu-lar (25) (left anterior descending), which lies in thegroove of the same name.

The right coronary usually supplies the sino-atrialnode (sixty per cent) and the atrioventricular node(ninety per cent). Branches of the coronary arteries doanastomose with each other, but not effectively enough toprevent myocardial ischaemia or infarction. The anteriorand posterior interventricular arteries send branchesinto the interventricular septum to supply the conduc-tive bundle of His and its branches. Arterial occlusionand consequent infarction may cause abnormalities ofcardiac rhythm. The posterior interventricular usuallycomes from the right coronary – right cardiac domi-nance. But it may be a continuation of the anteriorinterventricular, from the left coronary – left cardiacdominance. Narrowed (stenosed) coronary arteries,resulting in cardiac ischaemia, can be dilated with balloonangioplasty and metallic stents. Occluded coronary arter-ies may be surgically bypassed using grafts from the greatsaphenous vein, or from the internal thoracic artery.

The great cardiac vein (26) lies in the anterior inter-ventricular groove, but curves (with the circumflexartery) onto the posterior surface in the atrioventricu-lar groove. It becomes the coronary sinus (27) thatruns along the inferior surface of the left atrium toopen into the right atrium. Most cardiac veins are trib-utaries of the coronary sinus. But the anterior cardiacvein drains the wall of the right ventricle into the rightatrium. Many tiny veins are found within the cardiacmuscle, particularly on the right side. These are venaecordis minimae, and these drain directly into thechambers.

80 The Thorax

1 Superior vena cava2 Pulmonary trunk3 Left pulmonary artery4 Right pulmonary arteries5 Ascending aorta6 Left main bronchus7 Right main bronchus8 Right auricle9 Left auricle

10 Superior left pulmonary vein11 Inferior left pulmonary vein12 Right ventricle13 Small cardiac vein14 Posterior cusp of open

pulmonary valve

15 Left cusp of open pulmonaryvalve

16 Right cusp of open pulmonaryvalve

17 Left cusp of closed aortic valve18 Right cusp of closed aortic

valve19 Posterior (non-coronary) cusp of

closed aortic valve20 Right coronary artery in

atrioventricular groove21 Right marginal artery22 Posterior interventricular artery

in interventricular groove23 Left coronary artery

24 Circumflex branch of leftcoronary artery

25 Anterior interventricular branchof left coronary artery, ininterventricular groove

26 Great cardiac vein27 Coronary sinus in atrioventricular

(coronary) groove28 Left atrium29 Right atrium30 Inferior vena cava31 Left ventricle32 Apex of heart33 Left marginal artery

34 Middle cardiac vein in posteriorinterventricular groove

35 Left posterior ventricular vein36 Superior right pulmonary vein37 Azygos vein38 Tracheobronchial lymph nodes39 Inferior right pulmonary vein40 Anterior cusp of closed mitral

valve41 Posterior cusp of closed mitral

valve

A Heart, dissected (from the front)B Heart, dissected (from behind)C Pulmonary valve (open), aortic valve (closed) and mitral

valve (closed) (from behind)

D Aortic valve (closed) (from above)E Aortic valve (closed) (from below)

Heart: superior and exterior views 81

BA

C D

A

LR

P

3

10

11

2625

1

298

20

13

32

31

3

6

10

38

11 2836

41

3738

738

35 24

31 27

15

1214

22625

26

24

40

41 19

1817 5

20

23

16

1718

19

5

3422

1221

20

30

39 29

2525

26 33

9

1

12

S

LR

I

S

RL

I

A

LR

P

S

RL

I

E

19

18 17

Location of numbers: 1AB; 2AC; 3AB; 4B; 5ACD; 6B; 7B; 8A; 9A; 10AB; 11AB; 12ABC; 13A; 14C; 15C; 16C; 17CDE; 18CDE; 19CDE; 20ABC; 21B; 22B;23C; 24BC; 25AC; 26AC; 27B; 28B; 29AB; 30B; 31AB; 32A; 33A; 34B; 35B; 36B; 37B; 38B; 39B; 40C; 41C.

The breast, and the thoracic wallin respiration

Breast

The breast, for nutrition of the newborn, is a modifiedsweat gland, with fifteen to twenty lobes embedded infat (1), emptying into lactiferous ducts (2) and viaampullae under the areola (3) into the nipple (4).During pregnancy the lobes enlarge (like bunches ofgrapes). Males have rudimentary breast tissue.

The breast lies on the second to sixth ribs in themidclavicular line, on the deep fascia overlying pec-toralis major (5), serratus anterior (6), and the upperend of external oblique (7). An axillary tail may curveunder pectoralis major, pierce the deep fascia andenter the axilla. The submammary space, between thedeep fascia and the breast, allows it some movementin relation to the underlying muscle. Suspensory liga-ments (8) between the deep fascia and breast dermissupport the breast. These may shorten with tumourinvolvement and cause skin puckering. Similarly,advanced tumour may invade the submammary spaceand anchor the breast.

The position of the nipple and areola varies but usu-ally they are at the level of the fourth intercostal spacein the young female. They are pink (depending onrace) in the nulliparous female, but darken to palebrown after pregnancy. The areola has many seba-ceous glands, which have a lubricating, protectivefunction during suckling.

Branches of the internal thoracic and anterior inter-costal arteries (especially the third and fourth) supplythe breast medially, and superior thoracic, thoraco-acromial and lateral thoracic (9) branches of axillaryartery laterally. The arteries have equivalent veins.Lymph drainage usually follows the arteries. Mediallyit is to parasternal nodes alongside the internal tho-racic artery. Most lymph, seventy-five per cent, passeslaterally to the nodes of the axilla. However, breast can-cer, which is not uncommon (one in ten women), maydisrupt this. and direction may be altered, promotingspread across the midline, into the abdomen, into the ver-tebrae, up to the cervical nodes or down to the inguinalnodes. Lymph flow may be affected in the axillary nodescausing oedema of the upper limb (lymphoedema).

Respiration

The thorax is for respiration. Its expansion causes low-ering of the intrathoracic pressure (creating negativeintrapleural pressure), in turn causing air to flow downthe only opening into the thorax, the trachea. Thediaphragm bulges upward from the abdomen, and itsdescent increases the vertical diameter of the thorax.Elevation of the ribs increases the anteroposterior(AP) and lateral diameters.

There is dispute over the actions of the intercostalmuscles during respiration. It is generally acceptedthat they prevent indrawing of the chest wall duringinspiration and that the external intercostals elevatethe ribs for inspiration. The internal intercostal (11)and innermost layers seem to contribute in expiration.

During inspiration the ribs rotate around the axis oftheir necks (see p. 68). The downward-sloping ribbodies move upward, pushing the sternum upwardand forward to increase the AP diameter (pumphandle). Those ribs with sloping necks and costal car-tilages also splay outward to increase the lateral thoracicdiameter. The first four ribs are only able to moveupward due to their short, horizontal costal cartilagesand, in the case of the first rib, its horizontal neck.

During forced inspiration there is additional ever-sion of the seventh to tenth ribs, to add a furtherincrease in lateral diameter (bucket handle). This addi-tional movement is carried out by the diaphragm andis only possible in ribs seven to ten, in which the cos-totransverse facets are flat and permit gliding in addi-tion to the rotation of the neck described above. Anymuscle that can aid expansion of the thorax is anaccessory muscle of inspiration, for example sterno -cleidomastoid and pectoralis major. Excessive use ofthese muscles is most pronounced in disease states, suchas asthma.

Expiration, in its quiet phase is passive. It occurs byrelaxation and elastic recoil. Forced expirationrequires contraction of accessory muscles to compressthe thorax, or to compress the abdomen to force thediaphragm upward.

Rib fractures painfully limit respiration. Severe trauma,resulting in fracture of the ribs in more than one placemeans that the intervening segment ‘floats’. It is paradox-ically drawn inward on inspiration and forced outward onexpiration.

82 The Thorax

A B

C

D

1210

9

20

16 11

15

18 6

521

1917

22

1 34

7

613

3

5

1

8

8

4

214

4

D

S

PA

I

S

LR

I

S

PA

I

S

Lat(L)

M

I

1 Fat of breast2 Lactiferous duct3 Areola of breast4 Nipple of breast5 Pectoralis major6 Serratus anterior

7 External oblique8 Fibrous septae (suspensory

ligaments)9 Branches of lateral thoracic artery

10 Supraclavicular nerves11 Internal intercostal muscles

12 Fascia over pectoralis major13 Latissimus dorsi14 Condensed glandular tissue15 Xiphoid process16 Pectoralis minor17 Deltoid

18 Rectus abdominis19 Clavicle20 Jugular notch21 Body of sternum22 Cephalic vein in deltopectoral

groove

A Superficial dissection of the left breast (from the frontand left)

B Muscles of the thoracic wall (from the front)C Left breast (from the front)D Sagittal section through the left breast (from the left)

The breast, and the thoracic wall in respiration 83

Location of numbers: 1AD; 2D; 3AC; 4ACD; 5BD; 6AB; 7A; 8D; 9A; 10A; 11B; 12A; 13A; 14D; 15B; 16B; 17B; 18B; 19B; 20B; 21B; 22B.


The Abdomen

Part V

36 Full abdomen, peritoneum, position oforgans 86

37 Lower oesophagus and stomach 8838 Intestine 9039 The (vermiform) appendix, pancreas,

spleen 9240 Liver: lobes, surrounding peritoneum

and spaces 9441 Gall bladder, biliary tree, porta hepatis 9642 Kidneys 9843 Ureter, suprarenal (adrenal) gland 10044 Posterior abdominal wall muscles,

mesentery 10245 Anterior abdominal wall 104

Full abdomen, peritoneum,position of organs

The abdominal cavity extends upward, inferior to thediaphragm, under the lower ribs and costal margin. Itextends inferiorly into the pelvis, and the iliac bones(covered by iliacus and psoas) form the lower aspect ofthe posterior abdominal wall. The important bonylandmarks are: tip of the ninth costal cartilage, partic-ularly the right; anterior superior iliac spine; pubictubercle; pubic crest; pubic symphysis. The nineregions described during clinical examination of theabdomen are: left and right hypochondrium (A);epigastrium (B); left and right loin (lumbar) (C):umbilical (D); left and right iliac fossa (inguinal) (E);and suprapubic (F).

Peritoneum

Most of the gastro-intestinal tract and associatedorgans must be able to move and distend. They invagi-nate a ‘balloon’ of peritoneum (mesothelium) so thatthey are covered by visceral peritoneum, but hang ona mesentery (1) arising from the posterior abdominalwall.

The parietal peritoneum extends under thediaphragm, around the abdominal walls and into thepelvis. There is a layer of transversalis fascia betweenthe muscles and the peritoneum. The parietal peri-toneum receives sensory supply from the cutaneousnerves of the overlying skin. The phrenic nerves sup-ply the diaphragmatic peritoneum.

The peritoneal cavity is a potential, lubricated space intowhich blood, fluid and infection may spread rapidly:haemoperitoneum, ascites, peritonitis. Embryonic devel-opment of the peritoneal cavity and mesenteries ishighly complex. Most organs retain a mesentery poste-riorly but some appear to drop out of their mesenteryto lie on the posterior abdominal wall retroperi-toneally. Those suspended on a mesentery are describedas intraperitoneal and any rupture of the viscus will allowits contents to escape into the peritoneal cavity.

During the embryonic stage the lower oesophagus,stomach and first half of the duodenum also have ananterior, ventral mesentery. The liver (2,3) developsin this ventral mesentery, which transmits the umbili-cal vessels and has a free edge inferiorly. In the adult,

the ventral mesentery is the falciform ligament (4),from liver to diaphragm and anterior abdominal wall,and the lesser omentum from liver to stomach (5).

At the epiploic foramen the lesser sac of peritoneumextends behind the stomach and lesser omentum as adiverticulum from the greater sac. It provides a lubri-cated, potential space for movement and distension ofthe stomach. It may also be the site of abscess formationor of pancreatic pseudocysts. The epiploic foramen liesbehind the free edge of the lesser omentum, in frontof the inferior vena cava, above the first part of theduodenum (6) and below the caudate lobe of theliver.

The greater omentum (7) is a fat-filled fold of peri-toneum (derived from the embryonic dorsal mesen-tery of the stomach) that hangs off the inferior edge(greater curvature) of the stomach. It is often called the‘policeman of the abdomen’ as it appears to migratetoward, stick to, and seal off diseased organs to preventtheir rupture and consequent generalized peritonitis.

Organ positions

The liver and gall bladder (8) lie under the ribs andcostal margin above the right hypochondrium. Thespleen is high, on the left. The stomach is in theepigastrium. The small intestine lies centrally withmuch of the duodenum hidden retroperitoneally. Thejejunum (9) tends to lie to the upper left and theileum (10) to the lower right. The ileum may dropinto the pelvis.

The first part of the colon, the caecum (11) (withthe appendix), is in the right iliac fossa, usually havinglittle or no mesentery. The ascending colon ascends upthe right flank, retroperitoneally, in the paravertebralgutter. It turns to become the transverse colon at thehepatic flexure. The transverse colon (12) has its ownmesentery that attaches across the abdomen just infe-rior to the pancreas and duodenum. They both fuse tothe undersurface of the greater omentum. In the lefthypochondrium, the transverse colon turns as thesplenic flexure to become the descending colon thatruns in the left flank or paravertebral gutter, behindthe peritoneum. It continues as the sigmoid colon, inthe left iliac fossa, with a mesentery. The sigmoidcolon is mobile on its mesentery, often descendinginto the pelvis. It becomes the rectum.

86 The Abdomen

The ‘nine regions’ of the abdomenA Hypochondrium (left and right)B EpigastriumC Lumbar region or loin (left and

right)D Umbilical region

E Iliac fossa or inguinal region (leftand right)

F Hypogastrium or suprapubicregion

1 Mesentery

2 Left lobe of liver3 Right lobe of liver4 Falciform ligament5 Stomach6 Superior (first) part of

duodenum

7 Greater omentum8 Gall bladder9 Jejunum

10 Ileum11 Caecum12 Transverse colon

A Abdominal contents (from the front) with grididentifying the nine regions of the abdomen

B Abdominal contents with omentum reflected (from thefront)

Full abdomen, peritoneum, position of organs 87

A B

1110

27

12

9

10

1

7

7

7

5

42

3

AA B A

C D C

E F E

8

6

S

LR

I

S

LR

I

Location of numbers: 1B; 2AB; 3A; 4A; 5A; 6A; 7AB; 8A; 9B; 10AB; 11A; 12B.

Lower oesophagus and stomach

Masticated food and fluid pass via the oesophagus tothe stomach, a distensible sac that holds and digestsfood. At its distal end the pyloric sphincter is closedwhile acid and digestive enzymes are secreted to mixwith the food. Muscular action mechanically helps tofurther mix and digest the food. The pyloric sphincteropens periodically and the resultant chyme is passedinto the duodenum.

Lower oesophagus and cardio-oesophagealjunction

Having passed through the diaphragm (1), the oesoph-agus (2) enters the stomach. There is no dissectible,anatomical sphincter at the cardio-oesophageal junc-tion to maintain its closure and prevent reflux of gastriccontents into the oesophagus. The right crus of thediaphragm sweeps around the lower end of the oesoph-agus. There is a resting tone in the circular muscle layerat the lower end of the oesophagus to keep it closed,except during swallowing. The oblique angle at whichthe oesophagus enters the stomach creates a flap valve,which is elongated and augmented by the extra,oblique layer of muscle in the cardiac region of thestomach wall. All the above contribute to the physio-logical cardiac sphincter.

A hiatus hernia is where the stomach moves upthrough the oesophageal diaphragmatic opening (slid-ing), or a pouch of stomach may pass through the open-ing to lie alongside the oesophagus (rolling). In the firstcase, the cardiac sphincter is rendered ineffective.Oesophageal reflux of acidic gastric contents can thenoccur resulting in pain (heartburn). Erosion of the mucousmembrane of the lower oesophagus may follow, whichresults in oesophagitis.

The oesophageal plexus, formed by the left and rightvagus nerves, coalesces into anterior and posteriorvagal trunks. These pass through the diaphragm withthe oesophagus and continue along the upper lessercurvature (3) of the stomach to supply it, the acid-secreting glands and the pyloric sphincter. Surgically,the oesophagus can be pulled into the abdomen so thevagal trunks may be identified and resected (vagotomy) tocontrol excess acidity or overcome tight closure of thepyloric sphincter.

Portosystemic anastomosis

The gastro-intestinal tract drains to the liver via theportal vein, as does the lower end of the oesophagus(via the left gastric vein). The mid-oesophagus drainsto the azygos, part of the systemic circulation. Theportal and systemic circulations anastomose via veinsin the submucosa of the lower end of the oesophagus.Liver disease may cause portal hypertension, with portalblood escaping via portosystemic anastomoses into thesystemic circulation. The submucosal veins involvedbecome dilated to create oesophageal varices, which mayrupture and bleed.

Stomach

When empty the stomach is flattened and has a cardia(4), fundus (5), body (6), antrum (7), pylorus (8)and two curvatures, the short upper lesser curvatureand the much longer and lower greater curvature (9).The fundus lies posteriorly, to the left of the midline,against the spleen (10) and the diaphragm. On a plain,upright abdominal radiograph a bubble of gas is usuallyvisible in the fundus.

The oesophagus enters obliquely at the cardia. Thebody curves anteriorly as it passes to the right acrossthe epigastrium. To the right of the midline the bodyleads to the antrum (the site of greatest acidity) thatleads to the pyloric canal, through the pyloric sphinc-ter, close to the tip of the ninth right costal cartilage.The pyloric sphincter is a thickening of the circularmuscle layer. It is controlled by vagal (closure) andsympathetic (opening) nerve fibres. Some babies (usu-ally male) are born with hypertrophy of the pyloric sphinc-ter, causing the stomach to overfill and then empty byprojectile vomiting (pyloric stenosis).

Arterial supply

An anastomotic ring of blood vessels derived from thecoeliac trunk (axis), and its splenic and common hepaticbranches, surrounds the stomach. The right and left(12) gastric arteries supply the lesser curvature. The leftand right gastro-epiploics supply the greater curvatureand the short gastrics supply the fundus and pass fromthe splenic artery (28) in a double fold of peritoneumthat passes from the spleen to the stomach, the gastro -splenic ligament. There are equivalent veins (tributariesof the portal vein). Lymph drainage follows the arteriesto the para-aortic nodes around the coeliac trunk.

88 The Abdomen

1 Diaphragm2 Oesophagus3 Lesser curvature of stomach4 Cardiac region of stomach5 Fundus of stomach6 Body of stomach7 Pyloric antrum of stomach8 Pyloric canal of stomach

9 Greater curvature of stomach10 Spleen11 Inferior lobe of left lung12 Left gastric artery13 Gall bladder14 Aorta15 Left kidney16 Cystic duct

17 Bile duct18 Falciform ligament19 Head of pancreas20 Body of pancreas21 Tail of pancreas22 Superior (first) part of duodenum23 Descending (second) part of

duodenum

24 Horizontal (third) part ofduodenum

25 Left lobe of liver26 Caudate lobe of liver27 Right lobe of liver28 Splenic artery

A Upper abdominal contents (from the front)B Stomach, internal aspect (from the front)

Lower oesophagus and stomach 89

A

B

118

27

25

16 17

26

1319

22

8 14

724

23

25

10

11

21

159

3 6

20

28

12

1

9

8 73

4

5

62

9

S

LR

I

S

LR

I

Location of numbers: 1A; 2AB; 3AB; 4B; 5AB; 6AB; 7AB; 8AB; 9AB; 10A; 11A; 12A; 13A; 14A; 15A; 16A; 17A; 18A; 19A; 20A; 21A; 22A; 23A; 24A; 25A;26A; 27A; 28A.

Intestine

Chyme passes from the stomach (1) into the duode-num (2), where gastric acid is neutralized and furtherdigestive enzymes are added, particularly from thepancreas (3,4,5,6), and bile enters to aid the digestionof fat. Absorption commences in the duodenum, but isthe main function of the jejunum and ileum(Illustration B). The mucous membrane of the smallintestine is thrown into villi, and the submucosa isthrown into folds (9), all to create a huge, absorptivesurface area. The jejunal wall feels thicker than the ilealwall. There are lacteals in the centre of each villus.Digested fats are absorbed via the lacteals and carriedin the lymph channels of the mesentery (13) to the cis-terna chyli. Other nutrients are absorbed into theblood and carried to the portal vein (14).

The ileum enters the caecum with a valvular effectto prevent reflux from caecum to ileum (ileocaecalvalve). The stomach and small intestine secrete largeamounts of fluid to mix with the chyme. The colon(large bowel or intestine) is essentially for the reab-sorption of that fluid, to dry out what is now waste,and create faeces. Failure to reabsorb the fluid resultsin diarrhoea. The colonic wall (Illustration D) has novilli and only a few submucosal folds. The epitheliumis absorptive, and has many mucus-secreting cells tolubricate the faeces.

The external muscle layer of the large bowel con-denses into three strips (taenia coli (17)). The bowelwall tends to bulge between these strips as haustra-tions or sacculations (18). Tags of fat, appendices epi-ploicae, hang off the large bowel. These three featureshelp the surgeon differentiate the large from the smallbowel. Small pockets or diverticula may develop andextend from the wall of the large bowel, particularly fromthe sigmoid colon. Such diverticula may becomeobstructed, inflamed, and even perforate.

Blood supply to most of the intestine is by branchesof the superior mesenteric artery (19) until two-thirdsof the way around the transverse colon (20). At thatpoint, which is the transition from midgut to hindgut,branches of the inferior mesenteric take over.

Lymphocytes are scattered abundantly throughout theintestinal wall. In the ileum they aggregate as Peyer’spatches. The lymphoid tissue has a protective func-tion, and the lymph passes through the mesentericnodes on its way to the cisterna chyli.

The duodenum has four parts, which form a C-shaped curve around the head of the pancreas. Thefirst part is initially on a short mesentery, but curves tothe right and posteriorly (the ‘duodenal cap’ seen onbarium studies) to become retroperitoneal. It lies infe-rior to the epiploic foramen. The bile duct passes pos-teromedial to the first part, as does the gastroduodenalartery. Ulcers in the posterior wall of the duodenum mayerode into this artery and cause severe bleeding, or erodeinto the pancreas. Anterior ulcers may perforate into theperitoneal cavity.

The second part of the duodenum (25) is just to theright of the vertebral column (27) and inferior venacava (28). It overlies the hilum of the right kidney(35). The pancreatic and bile ducts (40) combine toopen on its posteromedial wall, as the major duodenalpapilla, about two-thirds of the way down. The firstpart, on its short mesentery is mobile. The secondpart, retroperitoneal, is fixed. Acceleration and deceler-ation accidents may cause duodenal rupture at this point.The third part curves over L3, anterior to the inferiorvena cava and aorta (41), just inferior to the pancreasand posterior to the superior mesenteric vessels.

The fourth part, just to the left of L2, lifts off theposterior abdominal wall, gains a short mesentery andturns to continue as the jejunum. As it gains a mesen-tery it may lift folds of peritoneum off the posteriorabdominal wall and create peritoneal pockets that may bethe sites of internal hernias.

Blood supply

The duodenum is supplied by the superior and inferiorpancreaticoduodenal arteries, derived from the coeliacaxis and superior mesenteric artery, respectively.Therefore, these latter arteries anastomose in the duo-denum. Equivalent veins drain to the portal vein.Lymph drainage follows the arteries to nodes on theaorta around the coeliac axis and superior mesentericartery.

90 The Abdomen

1 Body of stomach2 Superior (first) part of

duodenum3 Head of pancreas4 Body of pancreas5 Tail of pancreas6 Uncinate process of pancreas7 Right lobe of liver8 Gall bladder9 Submucosal folds, plicae

circulares10 Horizontal (third) part of

duodenum

11 Left lobe of liver12 Hepatic artery13 Mesentery of small bowel14 Portal vein15 Spleen16 Left kidney17 Taenia coli18 Haustration/sacculation of

colon19 Superior mesenteric artery20 Transverse colon21 Left gastric artery22 Greater omentum

23 Ascending colon and right colic(hepatic) flexure

24 Right gastro-epiploic artery25 Descending (second) part of

duodenum26 Jejunum27 Intervertebral disc between

second and third lumbarvertebrae

28 Inferior vena cava29 Descending colon30 Linea alba31 Rectus abdominis

32 External oblique33 Internal oblique34 Transversus abdominis35 Right kidney lower pole36 Cauda equina37 Psoas major38 Quadratus lumborum39 Erector spinae40 Bile duct41 Aorta42 Mesentery of sigmoid colon43 Falciform ligament

A Upper abdominal contents (from the front)B Small intestine, external and internal aspect (from the

front)

C Axial section through the abdomen (from below)D Large intestine, external and internal aspect (from the

front)

Intestine 91

A

B

D

C

28 4122

5

15

1

21

11 43

12 7

83

625

2

10 19

24

4

4014

16

9

19

13

18

42

17

30

22 2018

3122

13

23

284141

2737

38

3936

35 25

710

2726

29

32

3334

S

LR

I

S

LR

I

S

LR

I

L

IR

R

1926

29

32

Location of numbers: 1A; 2A; 3A; 4A; 5A; 6A; 7AC; 8A; 9B; 10AC; 11A; 12A; 13BC; 14A; 15A; 16A; 17D; 18CD; 19ABC; 20C; 21A; 22AC; 23C; 24A;25AC; 26C; 27C; 28AC; 29C; 30C; 31C; 32C; 33C; 34C; 35C; 36C; 37C; 38C; 39C; 40A; 41AC; 42D; 43A.

The (vermiform) appendix,pancreas, spleen

Appendix (vermiform) (Illustration C)

The appendix (1,2) hangs off the caecum (3), belowthe entry of the ileum (4), at the convergence of thethree taenia coli. It is a blind-ended tube of indetermi-nate function. The appendix is variable in its mesen-tery (5), its length and its position. It may lie behindor in front of the caecum or the distal end of theileum, or in the pelvis. The root of the appendix lies atMcBurney’s point – one-third of the way up a linefrom the anterior superior iliac spine to the umbilicus.

The lining of the appendix is the same as that of thecolon with the addition of nodules of lymphatic tissue.The lumen may become obstructed, and its wall swollenand inflamed. In turn, this inflammation may obstruct theappendicular artery as it runs along the length of theappendix causing gangrene and eventual perforation ofthe appendix. The variable position may make diagnosisdifficult. The early pain of appendicitis usually refers to themidline, in the umbilical region. It then becomes localizedin the right iliac fossa as progression of the disease affectsthe overlying parietal peritoneum. Pus, and/or the con-tents of a perforated appendix may spread throughoutthe peritoneal cavity.

Pancreas (Illustration D)

The pancreas secretes digestive enzymes into the duo-denum (exocrine). The cells in the islets of Langerhansalso have the endocrine function of secreting insulinand glucagon, which control blood sugar. The bile andpancreatic ducts combine to form the hepatopancre-atic ampulla (of Vater), which opens in the secondpart of the duodenum as the major duodenal papilla.There may also be an accessory pancreatic duct thatopens at a minor papilla just proximally.

The pancreas is retroperitoneal within the C-shapedcurve of the duodenum, and itself curves over the infe-rior vena cava and aorta before passing toward thehilum of the spleen. It has a head (7), neck (8), body(9) and tail (10). The uncinate process (11) extendsfrom the head and lies posterior to the superior

mesenteric vessels. Although most of the pancreas isretroperitoneal, the tail passes into a double fold ofperitoneum, which passes between the left kidney andthe spleen, the lienorenal ligament.

Blood supply

The splenic artery takes a tortuous course just poste-rior to the upper edge of the pancreas. It sends manysmall arteries, as well as the greater pancreatic arteryto supply the pancreas, along with the pancreatico-duodenal arteries. The splenic vein is posterior to thepancreas. It meets the superior mesenteric vein toform the portal vein behind the neck of the pancreas.

Pancreatitis is commonly caused by alcohol excess andgallstones. It results in the leakage of pancreatic digestiveenzymes into the overlying lesser sac.

Spleen (Illustration A,B)

The spleen has immunological functions. It is a ‘bloodfilter’ for old red cells and it stores white blood cells,especially lymphocytes. It lies posteriorly, high in theleft upper abdomen, under the diaphragm and abovethe stomach and left kidney. It is surrounded by peri-toneum, and the gastrosplenic and lienorenal ligamentsof peritoneum attach it to the stomach and to the pos-terior abdominal wall, adjacent to the left kidney.

As it lies against the diaphragm the spleen is relatedto the left ninth, tenth and eleventh ribs. This isextremely significant as fracture of these ribs may rupturethe spleen and cause considerable intraperitoneal bleed-ing. Blood from such a rupture may irritate the left hemi-diaphragm and refer pain to the left shoulder tip.

The splenic artery (12) and vein (13) and tail of pan-creas reach the hilum of the spleen in the lienorenal liga-ment. The vessels must be ligated during splenectomy, anoperation that may leave the patient susceptible to infec-tion, particularly from Pneumococcus and Haemophilusinfluenzae.

The spleen extends anteriorly if it enlarges (congestivecardiac failure, malaria, lymphomas) and it may be palpa-ble at the left costal margin when it is twice its normal size.This superior edge may have a palpable splenic notch(14).

92 The Abdomen

1 Base of (vermiform) appendix2 Tip of (vermiform) appendix3 Caecum4 Terminal ileum

5 Mesentery of appendix6 Ascending colon7 Head of pancreas8 Neck of pancreas

9 Body of pancreas10 Tail of pancreas11 Uncinate process of pancreas12 Splenic artery

13 Splenic vein14 Notch of spleen15 Inferior border of spleen16 Superior border of spleen

A Spleen (from the front)B Spleen (from below)

C Caecum and (vermiform) appendix (from the front)D Pancreas (from the front)

The (vermiform) appendix, pancreas, spleen 93

A B

D

C

16

12

13

14 14

16 14

16

14

12

1315

6

15

11

78 9

102

4

3

15

S

LR

I

A

LR

P

S

LR

I

S

LR

I

Location of numbers: 1C; 2C; 3C; 4C; 5C; 6C; 7D; 8D; 9D; 10D; 11D; 12AB; 13AB; 14AB; 15B; 16AB.

Liver: lobes, surroundingperitoneum and spaces

The liver is the largest gland in the body and has thefollowing functions: produce and secrete bile;metabolise, monitor and maintain blood glucose (glu-costat); metabolise and synthesise proteins, aminoacids and lipids; store minerals; store and synthesisesome vitamins; metabolise and detoxify drugs, toxinsand hormones; and – only in the fetus – haemopoiesis.

The liver is a soft, vascular organ that lies high in theabdomen, usually extending across the epigastriumand under the medial edge of the left costal margin. Itis a rounded wedge with the base lying posterosuperi-orly against the diaphragm and posterior abdominalwall. The ‘thin edge’ points antero-inferiorly towardthe costal margin but should not be palpable below thecostal margin in the healthy adult. It is divided into right(1) and left (6) lobes. Anatomically, the right lobealso has caudate (7) (posterior) and quadrate (8)(anterior) lobes. But these are functionally part of theleft lobe as they receive blood from the left branchesof the portal vein and hepatic artery.

To carry out its functions the liver receives venousblood from the spleen and gastro-intestinal tract viathe portal vein. As it is the first organ to receive toxinsingested from the digestive tract it may be particularlysusceptible to damage from those toxins. Damage tothe liver and/or obstruction to the biliary tree will causebile pigments to escape from the liver into the blood,causing jaundice, a yellow discoloration of the skin andsclera. Protein synthesis, particularly of plasma proteinsand clotting factors, may be disrupted in liver disease,causing such patients to bleed easily. The liver itself is sur-rounded by a thin fascial capsule, which is not substantial.As a result, it is susceptible to laceration and tearing indeceleration accidents and following fractures of the over-lying ribs.

Relations

The gall bladder (9) lies on the undersurface of theliver, between the right and quadrate lobes. The inferiorsurface of the right lobe is related to the right kidneyand suprarenal gland (10), the duodenum (11) and thehepatic flexure of the colon (12). The inferior surface

of the left lobe is related to the oesophagus (13) andstomach (14). The quadrate lobe and gall bladder relateto the pylorus and first part of the duodenum.

Peritoneum

In the embryo, the liver forms in the ventral mesen-tery, but the eventual adult position is as if the liverhad invaginated the peritoneum from above andbehind. The visceral peritoneum covers the liver andgall bladder and becomes parietal peritoneum as itreflects onto the diaphragm and posterior abdominalwall. The reflections form upper and lower (15) coro-nary ligaments both on the right and left sides. Theleft (16) and right (17) triangular ligaments areformed where the respective upper and lower coro-nary ligaments meet. On the left, the coronary liga-ments are so short that the reflections are usuallyreferred to as the left triangular ligament.

The coronary and triangular ligaments surround thebare area of the liver (18) that is related to the inferiorvena cava (19), right suprarenal gland and upper poleof the right kidney, lying on the diaphragm as it formsthe posterior wall of the upper abdomen.

The falciform ligament (20) separates the liver intoits anatomical right and left lobes. The ligamentumteres (21) is the obliterated left umbilical vein, lying inthe free edge of the falciform ligament.

Subhepatic and subphrenic potential peritonealspaces (Illustration A)

The left (A) and right (B) subphrenic spaces are oneither side of the falciform ligament, between the liverand the diaphragm. The right subhepatic space (C) isunder the right lobe of the liver, between it and thekidney. It communicates with the lesser sac via theepiploic foramen. The left subhepatic space (D) isunder the left lobe of the liver, between it and thelesser omentum. The lesser sac, behind the lesseromentum and caudate lobe may also be considered asa subhepatic space.

Theoretically, blood or pus from generalized peritonitismay collect in any of these potential spaces. The right sub-hepatic space is the most common (as patients are usuallyrecumbent) with the possible consequence of abscess for-mation.

94 The Abdomen

A

B C

1

2022

6

22 B

A

D

C

9

9

112

7

82120

6

1

12

11

15

1718

10

197

13

14

6

16

23

45

8

9

S

LR

I

S

LR

I

A

LR

P

Abdominal spacesA Left subphrenic spaceB Right subphrenic spaceC Right subhepatic or hepatorenal

space (pouch of RutherfordMorison)

D Left subhepatic space

1 Right lobe of liver2 Portal vein3 Hepatic artery4 Common hepatic duct5 Cystic duct6 Left lobe of liver7 Caudate lobe of liver8 Quadrate lobe of liver9 Gall bladder

10 Position of right kidney andsuprarenal gland in relation tothe undersurface of the liver

11 Position of duodenum in relationto the undersurface of the liver

12 Position of colon in relation tothe undersurface of the liver

13 Position of oesophagus inrelation to the undersurface ofthe liver

14 Position of stomach in relation tothe undersurface of the liver

15 Lower right coronary ligament16 Left triangular ligament17 Right triangular ligament18 Bare area of liver19 Inferior vena cava20 Falciform ligament21 Position of ligamentum teres22 Diaphragm

A Upper abdominal contents (from the front)B Liver (from the front)C Liver (from below)

Liver: lobes, surrounding peritoneum and spaces 95

Location of numbers: 1ABC; 2C; 3C; 4C; 5C; 6ABC; 7BC; 8BC; 9ABC; 10C; 11C; 12BC; 13C; 14C; 15C; 16C; 17C; 18C; 19C; 20AB; 21B; 22A.

Gall bladder, biliary tree, portahepatis

Biliary system

Bile is formed continually in the liver. It is stored andconcentrated in the gall bladder that then releases bilewhen necessary in response to a fatty meal, usuallymediated by the release of cholecystokinin.

The gall bladder (2), covered by peritoneum, lies ina fossa (bare of peritoneum) between the right (3) andquadrate (4) lobes of the liver. It has a fundus (5),body (6) and neck (7). The cystic duct (8) passesfrom the neck of the gall bladder to join the commonhepatic duct (9). As the two ducts join, they continueas the bile duct. The mucous membrane at the gallbladder neck folds and overlaps to form the spiralvalve. The cystic artery (12), which is usually a branchof the right hepatic, supplies the gall bladder, but vari-ations are common. Venous drainage is to the portalvein. Arterial anomalies are not uncommon in thisarea, e.g. the common hepatic artery, usually from thecoeliac, may occasionally arise from the superiormesenteric.

The bile duct lies in front of the portal vein and tothe right of the hepatic artery in the free edge of thelesser omentum. Just behind and to the left of the firstpart of the duodenum it is related to the gastroduode-nal artery. But the duct then runs through the head ofthe pancreas, to join the pancreatic duct and enter thesecond part of the duodenum at the major duodenalpapilla. The sphincter of Oddi has three parts, onearound the lower bile duct, one around the pancreaticduct (to prevent bile entering the pancreas), and onearound the combined duct just before the ampulla. Ifbile is not required the sphincter closes and bile can-not escape down the bile duct. Instead is passes via thecystic duct to the gall bladder. When the sphincter isopen flow reverses down the cystic duct and into thebile duct, to the duodenum.

The gall bladder is susceptible to stone formation andconsequent inflammation – cholecystitis. Pain may refer tothe epigastrium, in the midline. However, if the inflamma-

tion reaches the peritoneum on the undersurface of thediaphragm, it is detected by the phrenic nerve (C3,4,5)and may refer to the right shoulder tip. Pain may beelicited directly from an inflamed gall bladder by asking apatient to inhale while palpating beneath the costal mar-gin at the tip of the ninth right costal cartilage. Pain is apositive Murphy’s sign.

Jaundice has a number of causes. Pre-hepatic jaundiceis an overload of bilirubin (despite a normal liver) usuallybecause of excessive blood breakdown (haemolytic jaun-dice). Hepatic jaundice is a result of damage to the liver’scellular structure (hepatitis, cirrhosis). Post-hepatic jaun-dice is due to obstruction of the hepatic and/or bile ductscausing biliary back pressure into the liver and the leak-age of conjugated bilirubin into the blood.

Gallstones that migrate from the gall bladder and intothe bile duct may cause painful, intermittent jaundice.Carcinoma of the head of the pancreas, obstructing thebile duct from its outside, may cause painless, continuousjaundice. A stone obstructing the major duodenal papillamay cause bile to flow back into the pancreas via the pan-creatic duct to cause pancreatitis.

Porta hepatis and neurovascular supply

At the porta hepatis the portal vein (13) and hepaticartery (14) divide into left and right branches to enterthe liver. The left (15) and right (16) hepatic ductscarry bile from the liver and converge to form the(common) hepatic duct. The artery also brings auto-nomic innervation and has parallel lymph drainage,which eventually returns to nodes around the coeliactrunk. Lymph nodes at the porta may enlarge andobstruct biliary flow.

Blood from the portal vein (full of nutrients but de-oxygenated) and the hepatic artery (oxygenated) filterthrough the liver to converge on a variable number(two to four) of hepatic veins that drain directly intothe inferior vena cava. The (hepatic) portal vein isformed by the splenic and superior mesenteric veins.The inferior mesenteric usually joins the splenic, butmay join the superior mesenteric or join the portalvein just as it is formed.

96 The Abdomen

1 Inferior vena cava2 Gall bladder3 Right lobe of liver4 Quadrate lobe of liver5 Fundus of gall bladder

6 Body of gall bladder7 Neck of gall bladder8 Cystic duct9 Common hepatic duct

10 Left lobe of liver

11 Caudate lobe of liver12 Cystic artery13 Portal vein14 Hepatic artery15 Left hepatic duct

16 Right hepatic duct17 Falciform ligament18 Diaphragm

A Upper abdominal contents (from the front)B Liver, with gall bladder in coronal section (from below)

Gall bladder, biliary tree, porta hepatis 97

A

B

18

17

10

43

5 6

78 9

32

16 1512

1413

11

1

10

4

S

LR

I

A

LR

P

Location of numbers: 1B; 2B; 3AB; 4AB; 5A; 6A; 7A; 8A; 9A; 10AB; 11B; 12B; 13B; 14B; 15B; 16B; 17A; 18A.

Kidneys

The kidneys lie retroperitoneally, high on the posteriorabdominal wall. They filter the blood to produceurine. They are vital to the control of plasma sodiumlevel and of blood pressure via the secretion of renin.Renal disease often leads to hypertension. The kidneysalso synthesize erythropoietin, which stimulates thebone marrow to produce red blood cells and hydroxy-cholecalciferol (a derivative of vitamin D), which isimportant for maintaining serum calcium levels.

Renal fat (Illustration A) is the term often used toinclude the perirenal fat, renal fascia and pararenal fat.A thin, tough capsule (2) immediately surrounds thekidney, which is a delicate organ and therefore sur-rounded, and protected, by further layers of fat andfascia.

Perirenal fat is immediately outside the kidney cap-sule. Renal fascia encloses the kidney, suprarenal(adrenal) gland (3) and perirenal fat (4). It is derivedfrom, and is continuous with the transversalis fascia.The renal fascia is closely applied to the upper andlateral aspects of the kidney. But perirenal effusionsmay extend into its potential space inferiorly andmedially. Pararenal fat surrounds the kidney andadrenal, outside the renal fascia. It usually has a firmerconsistency than fat elsewhere in the body.

Relations

The hilum of the left kidney is at L1, and the right atL2. They cause an indentation or sinus on the medialborder of the kidney (Illustration B). The right kidneyis slightly lower than the left, being displaced by theliver. From its hilum, which is anteromedial, the kid-ney falls backward and laterally into the paravertebralgutter alongside psoas major. The upper aspects of thekidneys are related to the eleventh and twelfth ribs,and therefore lie on the diaphragm, moving on respi-ration. When attempting to palpate an enlarged kidney itis necessary to ask the patient to inhale. When operating

on the kidney care must be taken not to incise thediaphragm and possibly create a pneumothorax.Occasionally the diaphragm may be deficient posteriorly.The kidney is then directly related to the pleura.

As the kidney is retroperitoneal most of its anteriorrelations are separated from it by the peritoneum. Butstructures that are also retroperitoneal are directlyrelated the kidney and its renal fat. On the right theliver is anterior to the kidney, with the peritonealpouch of Rutherford Morison between. The upperpole of the kidney is directly related to the bare areaof the liver. Medially the duodenum (second part) isdirectly related to the kidney and its hilum, whereasthe ascending colon is similarly related to the lowerpole.

On the left the tail of the pancreas and the splenicvessels (5) directly cross the hilum of the kidney. Thedescending colon (6) is directly related to the lowerlateral pole. The stomach (7), spleen (8) and jejunum(9) are anterior relations, but with peritoneum inbetween. The lesser sac extends between the stomachand left kidney.

Internally, the kidney shows a peripheral cortex (10)around a medulla (11). The latter has pyramids (12),which become renal papillae that push into minorcalyces (13), the first part of the urinarycollecting/conducting system. The minor calyces con-verge into two or three major calyces (14), whichthemselves converge to form the renal pelvis (15).

Neurovascular supply

The hilum of the kidney has the renal vein (16) (or itsbranches) anteriorly, the renal pelvis becoming ureter(17) posteriorly, and the renal artery (18), with itsvariable branches in the middle. The inferior vena cava(IVC) is to the right of the midline, therefore the rightrenal vein is much shorter than the left. When operat-ing on the right kidney it is possible to tear the short renalvein from the IVC.

Nerves are derived from the coeliac plexus. Lymphdrains to para-aortic nodes.

98 The Abdomen

A B C

4 3

7 8

19

13

11

1012

19

15

14

1816

17

132

5

9 6

16

18

1

17

20

1618

3

4

21

17

S

LR

I

S

LR

I

S

LR

I

1 Suprarenal vessels2 Cut border of fibrous capsule

(inferior portion removed)3 Suprarenal (adrenal) gland4 Perinephric (perirenal) fat5 Position of tail of pancreas and

splenic vessels in relation to theanterior surface of the kidney

6 Position of descending colon inrelation to the anterior surface ofthe kidney

7 Position of stomach in relation tothe anterior surface of the kidney

8 Position of spleen in relation tothe anterior surface of thekidney

9 Position of jejunum in relation tothe anterior surface of thekidney

10 Renal cortex11 Renal medulla12 Medullary pyramid13 Minor calyx14 Major calyx

15 Renal pelvis16 Renal vein17 Ureter18 Renal artery19 Renal papilla20 Position of upper pole of kidney21 Position of lower pole of kidney

A Left kidney, encapsulated in fat (from the front)B The left kidney from the frontC The left kidney in coronal section from the front

Kidneys 99

Location of numbers: 1B; 2B; 3AB; 4A; 5B; 6B; 7B; 8B; 9B; 10C; 11C; 12C; 13C; 14C; 15C; 16ABC; 17ABC; 18ABC; 19C; 20A; 21A.

Ureter, suprarenal (adrenal)gland

Ureter

The ureter leaves the renal pelvis to run retroperi-toneally down the posterior abdominal wall. It is amuscular tube lined by urinary transitional epitheliumand peristaltic waves propel the urine to the bladder.If touched during surgery, the ureter will contract andappear to ‘worm’ on the posterior abdominal wall.

The ureter (1) lies on psoas major (3), posterior toall other structures except the genitofemoral nerve(4). It crosses the bifurcation of the common iliacartery (5) to enter the pelvis, then down and forwardto the bladder, which it enters obliquely to preventreflux. The right ureter passes behind the second partof the duodenum (6), the right colic and iliac vessels,the gonadal vessels, and the root of the mesentery.The left ureter also lies behind the gonadal vessels, aswell as the left colic vessels and the root of the sigmoidmesentery. The ureter is visualized on a plain abdominalradiograph as lateral to the tips of the lumbar transverseprocesses, anterior to the sacro-iliac joint and medial tothe ischial spine.

The ureter is supplied by the vessels that are adja-cent to it, and they also carry its nerve supply: renal,gonadal, iliac, and vesical or uterine.

Ureteric stones are not uncommon and may pass downthe ureter, referring severe pain to the loin and groin aswell as to the tip of the penis in the male. There are sup-posedly three narrowings where stones may be delayed,the pelvi-ureteric junction, the pelvic brim, and the pas-sage of the ureter through the bladder wall, but these nar-rowings are debatable.

Suprarenal (adrenal) glands (Illustration B)

The suprarenal glands lie at the upper, medial pole ofeach kidney, within the renal fascia. They areendocrine glands with a peripheral cortex and an inter-nal medulla.

The suprarenal medulla is like a modified sympa-thetic ganglion in that under the stimulation of pre-

ganglionic sympathetic nerves it secretes adrenalineand noradrenaline. The resultant sudden rise of thesehormones, usually in response to danger or stress givesthe typical ‘fight or flight’ response: increased cardiacrate and output; widely staring eyes with dilatedpupils; an inhibition of gastro-intestinal activity; andmany other sympathetic responses associated with asudden fright.

The suprarenal cortex is essential to life and involvedin the body’s reaction to stress. It has three layers thatsecrete different hormones. Aldosterone acts on thekidney for the maintenance of sodium and potassiumlevels. Cortisol and corticosterone affect carbohydratemetabolism, the body’s connective tissues and theimmune system. Sex hormones, particularly the maleandrogens, are secreted, but normally in insignificantamounts.

Both glands lie retroperitoneally on the crura of thediaphragm. The lesser sac and stomach are anterior tothe left suprarenal, while the bare area of the liver andinferior vena cava (IVC) are related to the right.

Each gland is supplied by branches from three arter-ies, but drained by one large vein. On the right thevein is short and enters the IVC, whereas on the left,the suprarenal vein enters the left renal vein. Thesuprarenals receive an abundant nerve supply from thesplanchnic nerves and coeliac plexus, which liesbetween them.

Tumours may be found in both the cortex and medulla.If the medulla is affected the symptoms are those of mas-sive stimulation of the sympathetic system (phaeochromo-cytoma). Should the glands fail, or require surgicalremoval the patient must regularly take corticosteroiddrugs.

The IVC (7) is to the right of the midline, therefore,the right suprarenal and right gonadal veins drain intoit. The left suprarenal and gonadal veins (8) drain intothe left renal vein (9), which passes anterior to theaorta, but behind the superior mesenteric artery,behind the pancreas, above the third part of the duo-denum. The IVC lies to the right of the aorta, the leftcommon iliac vein passes behind the right commoniliac artery.

100 The Abdomen

1 Ureter2 Renal artery3 Psoas major4 Genitofemoral nerve

5 Common iliac artery and vein6 Descending (second part) of

duodenum reflected superiorly7 Inferior vena cava

8 Gonadal vein9 Renal vein

10 Inferior mesenteric vein11 Aorta

12 Upper pole of kidney13 Lower pole of kidney14 Left suprarenal (adrenal) gland

A Posterior abdominal wall (from the front)B Left suprarenal gland (from the front)

Ureter, suprarenal (adrenal) gland 101

A B

6

12

13

9

2

10

7 8

1

3

5

4

11

14

S

LR

I

S

LR

I

Location of numbers: 1A; 2A; 3A; 4A; 5A; 6A; 7A; 8A; 9A; 10A; 11A; 12A; 13A; 14B.

Posterior abdominal wallmuscles, mesentery

The posterior abdominal wall includes the diaphragm,psoas major and iliacus, quadratus lumborum andtransversus abdominis. The individual muscles are sur-rounded by their fascial sheaths (epimysium) and theyare all overlain internally by variable, often indistin-guishable, transversalis fascia.

The vertebral column (T12–L5) is prominent in themidline, with the aorta and inferior vena cava on itsanterior surface. On either side are two paravertebralgutters. The convexity of the lumbar vertebrae pushesinto the abdomen, therefore, structures passing trans-versely across the posterior abdominal wall must curveover the vertebrae.

Muscles and nerves

Psoas major (1) lies on each side of the vertebral col-umn, arising from the five lumbar vertebrae, theirintervening discs and the transverse processes. It passesinferiorly to join iliacus (2), arising from the internalaspect of the iliac bone, and form the iliopsoas tendonthat inserts onto the lesser trochanter of the femur.Iliopsoas is a hip flexor. Psoas is supplied segmentallyby L1–4 and iliacus by the femoral nerve.

The lumbar plexus is formed within psoas by theventral rami of T12–L5. The resultant nerves emergeonto the posterior abdominal (and pelvic) walls in anextremely variable pattern but usually described as:subcostal T12; ilio-inguinal (3) and iliohypogastricL1; lateral cutaneous nerve of thigh (lateral femoralcutaneous) (4) L2,3; genitofemoral L1,2; femoralL2,3,4; obturator L2,3,4; and lumbosacral trunk L4,5.The subcostal, ilio-inguinal and iliohypogastric nervessupply the lower parts of the abdominal wall muscles,and the skin of the lower abdomen and anterior aspectof the genitalia. The others pass to the skin and mus-cles of the thigh and leg.

Quadratus lumborum (5) attaches to the posterioriliac crest, the twelfth rib and the lumbar transverseprocesses. It stabilizes and laterally flexes the vertebralcolumn. It fixes the twelfth rib during deep inspira-

tion. With its neighbour, quadratus lumborumextends the vertebral column. The nerve supply is seg-mental, T12–L3.

Transversus abdominis (6) arises from: the internalaspect of the lower six costal cartilages; the thora-columbar fascia (which is a strong fascia around erec-tor spinae and quadratus lumborum); the iliac crest;and the inguinal ligament. It runs horizontally aroundthe abdomen to insert into the rectus sheath and lineaalba. It acts with the other abdominal wall muscles tosupport and compress the abdominal viscera. Thenerve supply is segmental, T7–L1.

Mesentery

The mesentery (7) is a fan-shaped double fold of peri-toneum that contains a variable amount of fat alongwith the superior mesenteric artery, vein and associ-ated nerves, lymph vessels and lymph nodes.

The root (origin) of the mesentery is 15 cm long. Itstarts to the left of L2 and passes obliquely downwardand to the right, to end opposite the right sacro-iliacjoint. It crosses: the fourth and third parts of the duo-denum; the aorta, where the superior mesentericartery enters it; the inferior vena cava; and the rightureter. The distal end is approximately 6 m long toaccommodate the length of the jejunum and ileum.

Within the mesentery the superior mesenteric arterysplays into jejunal, ileal and caecal branches. It hasalready sent the middle colic artery into the mesenteryof the transverse colon, and will send the right colicartery, retroperitoneally to the ascending colon. Thejejunal and ileal branches anastomose with each otherin a series of arterial arcades. The jejunum has fewarcades, with long vessels passing to it. The ileum hasmultiple arcades, with short vessels passing to it. Thispattern, along with the fact that the jejunal mesentery hasless fat than the ileal, may help the surgeon identify theparts of the bowel. Equivalent veins converge on thesuperior mesenteric vein.

The lymph nodes within the mesentery may becomeinfected and enlarged. The blood vessels may becomeoccluded and in spite of the anastomotic arcades, part ofthe bowel may become ischaemic.

102 The Abdomen

1 Psoas major2 Iliacus3 Ilio-inguinal nerve4 Lateral cutaneous nerve of thigh5 Quadratus lumborum

6 Transversus abdominis7 Mesentery8 Kidney9 Stomach

10 Body of pancreas

11 Gall bladder12 Left lobe of liver13 Promontory of sacrum14 Ureter15 Femoral nerve

16 Common iliac artery and vein17 Aorta18 External iliac artery and vein

A Posterior abdominal wall (from the front)

Posterior abdominal wall muscles, mesentery 103

A

12

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9 8

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Anterior abdominal wall

On each side, the anterior abdominal wall has one lon-gitudinal muscle, rectus abdominis (1), and three thatsweep around it, become aponeurotic and contributeto the rectus sheath (2) before fusing in the linea alba(3). They pass from the thoracic cage to the pelvis,and have the following functions: abdominal compres-sion to raise the intra-abdominal pressure during defe-cation, micturition, parturition and forced expiration,including coughing and sneezing; support of theabdominal contents; and support, flexion and lateralflexion of the lumbar vertebral column.

External to the muscular layers the superficial fasciahas a distinct membranous layer that thickens inferi-orly as Scarpa’s fascia to support the weight of the vis-cera. Internally, a layer of transversalis fascia liesbetween the musculature and the parietal peritoneum.

Surgical incisions are frequently made through theabdominal wall. It is important to know the directions ofthe muscle fibres, and the positions and directions of theneurovascular bundles to understand why some incisionsare used. Inferiorly, the inguinal canal is a potential site ofhernias (see pp. 168 and 169).

External oblique (4) (T7–12) arises from the lowereight ribs (interdigitating with serratus anterior andlatissimus dorsi). It passes inferomedially, with a freeposterior margin, to the outer lip of the anterior halfof the iliac crest. At the anterior superior iliac spine(ASIS) (5) it forms an aponeurosis that in rollsbetween the ASIS and the pubic tubercle (6) as theinguinal ligament (7). At the pubic tubercle, theinguinal ligament curves back upon itself as the lacu-nar ligament, to reach the pectineal line and end as thepectineal ligament. The superficial inguinal ring (8) isan opening in the aponeurosis, immediately above thepubic crest. The muscle fibres become aponeurotic ata line between the ASIS and the umbilicus (9). One-third of the way up this line is ‘McBurney’s point’(10), the site of incision for appendicectomy.

Internal oblique (11) (T7–L1) is deep to externaloblique and the muscle fibres are at right angles to it,

running superomedially. Internal oblique attaches tothe costal margin, the lumbar fascia, the iliac crest andthe lateral two-thirds of the inguinal ligament. Thefibres arising from the ligament arch over the inguinalcanal and fuse with similarly arching fibres of transver-sus abdominis to form the conjoint tendon.

Transversus abdominis (12) (T7–L1) forms thedeepest muscle layer. The fibres run transversely andattach to the lower six ribs and costal cartilages (inter-digitating with the diaphragm), the lumbar fascia, theiliac crest and the lateral half or one-third of theinguinal ligament. These lower fibres arch over theinguinal canal to form the conjoint tendon. The con-joint tendon is continuous with the anterior rectussheath and attaches to the pubic crest and medial endof the pectineal line, behind the superficial inguinalring.

The inferior epigastric artery, with accompanyingveins (13) arises from the external iliac at the mid-inguinal point, which is just medial to the mid point ofthe inguinal ligament. It ascends towards the umbili-cus and enters the rectus sheath (14) where it anasto-moses with the superior epigastric artery. The inferiorepigastric is at risk during the insertion of instruments forlaparoscopy.

The neurovascular bundles in the seventh toeleventh intercostal spaces, the subcostal bundle infe-rior to the twelfth rib, and branches of the L1 spinalnerve, curve inferomedially around the abdominalwall between internal oblique and transversus abdo-minis. They send cutaneous branches, segmentally, tothe skin, parietal peritoneum, and the muscles. At avariable distance anterior to the ASIS they pierceinternal oblique to run posterior to the aponeurosis ofexternal oblique. The ilio-inguinal branch of L1 is at alower level, just above the inguinal ligament. As itpasses to lie deep to external oblique it is in theinguinal canal and emerges from the superficial ring tosupply adjacent skin.

Surgical incisions should avoid cutting the nerves, andany reflection of rectus abdominis should be done in a lat-eral direction – towards the nerves that are entering andsupplying it (see pp. 167 and 169).

104 The Abdomen

1 Rectus abdominis2 Rectus sheath3 Linea alba4 External oblique5 Anterior superior iliac spine

6 Pubic tubercle7 Position of inguinal ligament8 Superficial inguinal ring9 Umbilicus

10 McBurney’s point

11 Internal oblique12 Transversus abdominis13 Inferior epigastric artery and vein14 Arcuate line, free edge of

posterior rectus sheath

15 Mons pubis16 Pyramidalis

A Muscles of the anterior abdominal wall, external (fromthe front)

B Muscles of the anterior abdominal wall, internal (frombelow)

Anterior abdominal wall 105

A B

31

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15

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7

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41

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Location of numbers: 1AB; 2AB; 3A; 4A; 5A; 6A; 7A; 8A; 9A; 10A; 11B; 12B; 13B; 14B; 15A; 16A.


The Male andFemale Pelvis

Part VI

46 Pelvic floor, ischio-anal fossa 10847 Urogenital triangle, external genitalia 11048 Penis, clitoris 11249 Testes, seminal vesicles, prostate gland 11450 Bladder, female urethra, vagina 11651 Pelvic ureter, male urethra 11852 Rectum, anal canal 12053 Ovary, uterine tubes 12254 Uterus, cervix 124

Pelvic floor, ischio-anal fossa

The pelvic cavity is superior to the muscular pelvicfloor (or diaphragm), and the perineum is inferior toit. The sacrospinous ligament (1) gives origin to someof the pelvic floor muscles. The lesser sciatic foramen(2) lies inferior to the ligament, therefore inferior tothe pelvic floor. Nerves and vessels passing throughthe lesser sciatic foramen enter the perineum, as dostructures that pass through the pelvic floor.

Pelvic floor muscles

The lateral wall of the true pelvis gives origin to obtu-rator internus (3), a lateral rotator of the hip. Themuscle is covered by obturator fascia that has a thick-ened ‘white line’ (4) running from the ischial spine tothe pubic body. The pelvic floor supports the pelvicorgans. The floor must not only expand, but also con-tract, as it contributes to the sphincteric control ofsome of the emerging organs, and therefore, it must bemuscular.

Coccygeus and levator ani arise in continuity witheach other; coccygeus (5) from the sacrum, coccyxand sacrospinous ligament; levator ani (6) from theischial spine, white line of obturator fascia and poste-rior aspect of the body of the pubis. Both muscles passdownward and medially to form a midline raphe thatpasses from the coccyx (7) to the pubic symphysis (8).The raphe is thickened between the coccyx and analcanal as the anococcygeal ligament (9) and anterior tothe anal canal as the perineal body, or central tendonof the perineum. The raphe is pierced by the analcanal (10), urethra (11) and, in the female, thevagina.

Levator ani is subdivided into iliac and pubic parts.Iliococcygeus and pubococcygeus insert into the coc-cyx and anococcygeal ligament. Puborectalis loopsaround the anorectal junction to fuse with its neigh-bour from the other side and draw the anorectal junc-tion up and forward. Pubovaginalis loops around thevagina to create a sphincteric effect around both it and

the urethra. In the male pubovaginalis is replaced bylevator prostatae that supports the prostate gland.

The perineal branches of S3 and S4 supply levatorani, along with branches from the pudendal nerve(S2,3,4). Branches of S5 supply coccygeus.

During childbirth the pelvic floor and/or perineal bodymay be damaged. Tears may need to be sutured, andpelvic floor exercises become necessary to rebuild sup-portive muscle tone. Laxity of the pelvic floor may allowthe pelvic organs to slip from their normal anatomicalpositions, possibly compromising urinary control, leadingto incontinence. In extreme cases the pelvic organs mayprolapse into and even right out of the vagina.

Perineum

The diamond-shaped perineum is bounded by: theischial tuberosities (12), covered by obturator inter-nus and obturator fascia; the sacrotuberous ligaments(13); the ischiopubic rami (14); and the inferior endof the pubic symphysis. It is divided into a posterioranal triangle and an anterior urogenital triangle. Theischio-anal fossa (15) is a pyramid with its base cov-ered by skin, its lateral aspect formed by obturator fas-cia, and its medial aspect formed by levator ani andthe anal canal surrounded by its external sphincter. Itis filled with fat to allow distension of the anal canalduring defecation.

The pudendal neurovascular bundle (16) of internalpudendal artery and vein, and the pudendal nerve(S2,3,4), leaves the pelvis to enter the buttock bypassing between piriformis (17) and coccygeus. It thencurves around the ischial spine and sacrospinous liga-ment to enter the ischio-anal fossa, lying on its lateralwall in a fascial (Alcock’s) canal on obturator internus.It passes forward to supply the perineal structures. Theinferior rectal neurovascular bundle (18) arises highup in the fossa and runs on levator ani to supply theanal sphincter and sensation to the anal canal.

The fat in the fossa is prone to infection and abscess for-mation. Such an abscess may extend forward into a recessbetween the pelvic floor and the deep perineal pouch, theanterior recess of the ischio-anal fossa.

108 The Male and Female Pelvis

1 Sacrospinous ligament2 Lesser sciatic foramen3 Obturator internus4 Obturator fascia, white line,

origin of levator ani5 Coccygeus6 Levator ani7 Coccyx

8 Pubic symphysis9 Anococcygeal ligament

10 Anal canal11 Urethra12 Ischial tuberosity13 Sacrotuberous ligament14 Ischiopubic ramus15 Ischio-anal fossa

16 Pudendal artery, vein and nerve17 Piriformis18 Inferior rectal artery, vein and

nerve19 Obturator nerve20 Lumbosacral trunk21 Ventral ramus of first sacral

nerve

22 Ventral ramus of second sacralnerve

23 Ventral ramus of third sacralnerve

24 Left sciatic nerve25 Promontory of sacrum26 Gluteus maximus27 Gluteus medius

A Left pelvic floor (from the right)B Bones and ligaments of the pelvis (from the front)C Male perineum (from below)D Female ischio-anal region (from behind)

Pelvic floor, ischio-anal fossa 109

B

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A

A

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1920

2124

2223

25

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11

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126

10

26

315

10

96

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1412

27

17

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18

27

24

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7 14

12

113

2

17

56

83

4

Location of numbers: 1B; 2B; 3AD; 4A; 5A; 6ACD; 7BD; 8AB; 9D; 10CD; 11C; 12BCD; 13BD; 14BCD; 15CD; 16D; 17AD; 18D; 19A; 20A; 21A; 22A; 23A;24AD; 25B; 26D; 27D.

Urogenital triangle, externalgenitalia

The urogenital triangle has deep and superficial per-ineal pouches, above and below the perineal mem-brane, a triangular sheet of fascia (stronger in the maleto support the penis) that attaches to the ischiopubicrami to span the sub-pubic angle. In the midline thebase of the membrane attaches to the perineal body(1).

The deep perineal pouch or urogenital diaphragm isa ‘sandwich’ of fascia and muscle. The perineal mem-brane is the outer, inferior layer. The external urethralsphincter and the deep transverse perineal musclesthat help fix and stabilize the structures within theregion, lie above it. The fascia on the superior surfaceof these muscles forms the deeper, superior layer ofthe pouch. The superficial perineal pouch is inferior orsuperficial to the perineal membrane and contains theexternal genitalia.

The scrotum houses both testes, so that they lie out-side the body cavity, at a slightly lower temperature.The skin is rugose (2), darker than skin elsewhere andis covered with pubic hair. There is a midline raphe,which stops at the anus (3), but continues with theraphe on the ventral surface of the penis. The superfi-cial fascia (Colles’) is fat free, continuous with thesimilar layer in the penis, abdominal wall and upperthigh, but it fuses with the perineal body. It containsdartos muscle (4) that contracts during cold or exer-cise to raise the testes closer to the body (see p. 168).

The labia majus (5) are thick folds of skin that meetanteriorly over the pubic symphysis as the mons pubis(6). Posteriorly they narrow and meet in the posteriorcommissure (7). Externally the mons and labia arecovered by pubic hair. Internally the skin becomesthinner and is pink and moist. The thickness of eachlabium is created by fibro-fatty tissue, into which theround ligament of the uterus inserts.

Vascular supply is via the external pudendal arteriesand veins anteriorly, and the posterior scrotal or labialbranches of the internal pudendal arteries and veinsposteriorly. Lymph drainage is to the superficialinguinal nodes.

Scrotal and labial nerve supply is also divided intothe anterior third and posterior two-thirds. In the scro-tum these sensory nerves carry sympathetic fibres todartos. The ilio-inguinal and genital branch of gen-itofemoral are anterior (L1). The posterior scrotal orlabial branches of the pudendal (S2,3,4) and theperineal branches of the femoral cutaneous nerve ofthe thigh (S2,3) are posterior.

The labia minora are thin, fat-free folds of pink,moist skin that lie within, and hidden by the labiamajora. Posteriorly they fade by merging with thelabia majora. Anteriorly they split into lateral andmedial folds, which fuse with those from the oppositeside to form the prepuce of the clitoris (8).

The vaginal vestibule, between the labia minora, iscovered by similar pink, moist skin. The vaginal open-ing (9) is small in the young and incompletely closedby the hymen. Occasionally the hymen completelycloses the vagina. Such closure may only become appar-ent at puberty with the commencement of menstruation.Once the hymen has been ruptured it is visible only asa few folds of skin, the carunculae hymenales, at thevaginal opening. The slit-like urethral opening (10) isimmediately anterior to the vaginal opening.

The bulbs of the vestibule (11) are the equivalent ofthe penile bulb (p. 112), but are divided into twohalves by the vagina and urethra. Each bulb of erectiletissue is overlain by bulbospongiosus muscle. They areattached to the superficial surface of the perinealmembrane, meeting only in an anterior commissure infront of the urethra. Their function is uncertain.Hidden under the posterior end of each bulb is agreater vestibular (Bartholin) gland (13) that opensinto the vaginal opening or the immediately adjacentvestibule. These secrete lubricating mucus and areaided by para-urethral and lesser vestibular glands,whose secretions reach the vestibule via minute ducts.The greater vestibular glands may become infected andcause a painful abscess.

Branches of the internal pudendal artery and equiv-alent veins supply the structures between the labiamajora. Each bulb receives an artery to the bulb. Thebranches anastomose freely to supply the overlyingskin and labia minora. Lymph drainage is to iliacnodes.


A B

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1 Position of perineal body2 Rugose scrotal skin3 Anus4 Superficial scrotal (dartos)

fascia

5 Labium majus, internal surface6 Position of mons pubis overlying

pubic symphysis7 Posterior commissure8 Prepuce of clitoris

9 Vaginal opening10 Urethral opening11 Bulb of vestibule12 Crura of clitoris, fusing to form

clitoris

13 Left greater vestibular (Bartholin)gland (bulb of vestibule dis-sected away)

A Left testis, epididymisand penis from the left

B Female perineum frombelow

C Female perineum fromthe front

Urogenital triangle, external genitalia 111

Location of numbers: 1B; 2A; 3B; 4A; 5B; 6B; 7B; 8B; 9B; 10B; 11BC; 12C; 13C.

Penis, clitoris

The penis has three corpora that form its root proxi-mally and its body more distally. The penis transmitsthe urethra for the passage of urine or semen.Anatomically, the penis is described as if erect.

The corpora cavernosa (1) commence as the twocrura, each one attached to the ischiopubic ramus andsurrounded by ischiocavernosus muscle (2).Anteriorly, immediately below the pubic symphysisthe crura lie side by side, fuse with each other, andpass into the dorsal aspect of the penis. They aretubes, surrounded by thick fascia, the tunica albuginea(3), and full of cavernous tissue that fills with blood toproduce erection. Ischiocavernosus, supplied bybranches from the perineal branch of the pudendalnerve (S2,3,4) compresses the crus to maintainerection. Each crus receives a deep artery of the penis,from the internal pudendal. The corpora cavernosacommunicate with each other across the midline sep-tum (created by their fused fascial sheaths) to enablepressure equalization so that erection is straight.

The corpus spongiosum (4) commences as the bulbof the penis, which is in the midline and attached tothe perineal membrane. It receives the urethra (5) andis surrounded by bulbospongiosus muscle (6). Thecorpus spongiosum continues onto the ventral aspectof the penis and distally it forms the glans penis (7),which is a cap over the two corpora cavernosa. It is atube of cavernous tissue, but its surrounding fascia isthin, therefore, the internal pressure during erectiondoes not occlude the urethra. The three corpora aresurrounded together by a layer of deep fascia, which isitself surrounded by superficial fascia and skin.Proximally the deep fascia is connected to the pubicsymphysis by the suspensory ligament of the penis.

The clitoris, like the penis, commences as the cruraattached to the ischiopubic rami and covered byischiocavernosus muscle (8). The crura continue asthe corpora cavernosa that meet, fuse and communi-cate with each other but are only about 2.5 cm long.They are together surrounded by deep fascia and sup-ported by the suspensory ligament (9). But there is no

corpus spongiosum and distally the glans of the clitorisis a little isolated cap of erectile tissue, covered byhighly sensitive thin skin, and surrounded by the pre-puce.

Penile skin is fat free, loose and mobile. Distally itturns inward upon itself and fuses with the rim orcorona (10) of the glans to create the foreskin (pre-puce) (11). The skin surface inside the prepuce is con-tinuous with that of the glans and the stratifiedsquamous epithelium becomes a mucous membrane.The foreskin must be retractable, otherwise the smegmaformed by the desquamation of cells into the spacebetween the foreskin and glans may become infected. Anon-retractable prepuce is usually surgically removed (cir-cumcision).

Blood and nerve supply

Blood supply to the penis and clitoris is via branches ofthe internal pudendal arteries and equivalent veins. Adeep artery supplies each crus and corpus cavernosum.

The penis has arteries to the bulb, to supply it, thecorpus spongiosum and the glans. There are also dor-sal arteries (12), under the deep fascia on the dorsumof the penis to supply the skin, glans and corpora cav-ernosa. Equivalent veins drain into the prostaticplexus. There is usually a single deep dorsal vein lyingwithin the deep fascia between the dorsal arteries.There is often an additional single or paired superficialdorsal vein (13), outside the deep fascia, on the dor-sum of the penis and draining to the external puden-dal vein, which is a tributary of the great saphenous.

The clitoris has dorsal arteries that pass on its dorsalsurface to supply the glans and prepuce, with the dor-sal vein lying between them. (There are not the deepand dorsal veins as in the penis).

Lymph drainage is to the superficial inguinal nodes.Nerve supply to the skin of the proximal penis is viaL1, the ilio-inguinal nerve. But the rest is supplied bythe dorsal nerve of the penis (14), which is the con-tinuation of the pudendal nerve (S2,3,4). Clitoralnerve supply is via the dorsal nerve of the clitoris andperineal branches of the pudendal nerve. These alsocarry sympathetic fibres from the pelvic plexus.


A

B

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7

16

12

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1

2

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6

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1410

17

19

18

15

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1 Corpora cavernosa of penis2 Ischiocavernosus3 Tunica albuginea4 Corpus spongiosum5 Urethra

6 Bulbospongiosus7 Glans penis8 Crus of clitoris and ischio -

cavernosus9 Suspensory ligament of clitoris

10 Corona of glans11 Foreskin (prepuce) of penis12 Dorsal artery, vein and nerve13 Superficial dorsal vein14 Superficial dorsal nerve

15 External urethral orifice16 Lateral superficial vein17 Testis18 Pampiniform venous plexus19 Vas (ductus) deferens

A Left testis, epididymis and penis from the leftB Male perineum from the frontC Female perineum from the front

Penis, clitoris 113

Location of numbers: 1B; 2B; 3B; 4B; 5B; 6B; 7A; 8C; 9C; 10A; 11A; 12AB; 13A; 14A; 15A; 16A; 17A; 18A; 19A.

Testes, seminal vesicles, prostategland

The testes

The testes are the paired oval-shaped male gonads thatsecrete sex hormones as well as creating sperm. Eachtestis is surrounded by a tough white fascial coat, thetunica albuginea (1), which facilitates sperm transportby maintaining a slight positive pressure within thetestis.

The seminiferous tubules create and transportsperm. They converge into tubules, the rete testis thatleads to the head of the epididymis (2) that is appliedto the posterior aspect of the testis. The epididymis isa hugely coiled tube for transport and maturation ofsperm. It has a head, body (3) and tail (4). At the infe-rior pole of the testis the tail becomes the vas or duc-tus deferens that is also convoluted at itscommencement.

The vas (ductus) deferens (5) ascends medial to theepididymis, up the posterior aspect of the testis in thespermatic cord, and then through the inguinal canal. Itenters the abdomen at the deep inguinal ring, immedi-ately lateral to the inferior epigastric artery and vein(6). It passes inferiorly, onto the lateral pelvic wall andthen across the pelvic floor (above the ureter) to meetthe duct of the seminal vesicle. Just before doing so itdilates as the ampulla of the vas.

The seminal vesicles

The seminal vesicles (7) lie, one on each side, poste-rior to the base of the bladder (8), extending laterallyposterior to the ureter (9,10). The duct from eachvesicle fuses with the vas deferens to create an ejacu-latory duct that passes through the prostate gland(11) to enter the urethra. The vesicle is about 5 cmlong and secretes seminal fluid, which is slightly alka-line and rich in fructose for nourishment of sperm.

The artery to the vas, from the inferior vesical

branch of the internal iliac artery supplies the vas andseminal vesicles. Venous drainage is via the prostaticplexus. The seminal vesicles receive sympatheticinnervation from the pelvic plexus and lymph drainsto the iliac nodes.

The prostate gland

The prostate gland is normally the size of a chestnutand is conical in shape, with its base related to thetrigone of the bladder and its apex piercing the pelvicfloor (12). It secretes a watery, slightly acidic andenzyme-rich (acid phosphatase) fluid to facilitate thepassage of sperm.

The glandular element of the prostate is within afibromuscular stroma, and the whole is surrounded bythick pelvic fascia, anchoring the gland to the pelvicfloor, and becoming the puboprostatic ligaments thatfix the gland to the pubic bone. Posteriorly, the lowerrectum (13) is separated from the prostate by therectovesical fascia (14) (fascia of Denonvilliers) thatcontains the ampulla of the vas and the medial parts ofthe seminal vesicles.

The urethra (15) and ejaculatory ducts are said todivide the prostate into lobes, with a median lobe lyingbetween the ejaculatory ducts and the neck of thebladder (16). Prostatic hypertrophy is extremely com-mon with increasing age. The median lobe may pushupward into the bladder neck and urethra, possibly dis-turbing continence, and definitely obstructing urinaryflow. Although general prostatic enlargement is palpableby rectal examination, enlargement of this so-calledmedian lobe towards the bladder may not be.

Prostatic branches of the inferior vesical artery sup-ply the prostate. There is a large plexus of veins in itssurrounding fascia. These drain to the internal iliacvein. But they also anastomose with veins entering thevalveless plexus of internal vertebral veins, facilitating thespread of prostatic tumour to the vertebral column.Lymph drainage is to the iliac nodes. The pelvicplexus provides sympathetic supply.


1 Tunica albuginea around testis2 Head of epididymis3 Body of epididymis4 Tail of epididymis5 Left vas (ductus) deferens6 Inferior epigastric vessels

7 Left seminal vesicle8 Base of bladder9 Right ureter (distal end)

10 Left ureter11 Prostate gland12 Cut edge of levator ani

13 Rectum14 Rectovesical fascia15 Urethra16 Neck of bladder17 Pubic symphysis18 Superior vesical artery

19 Corpus cavernosum20 Bulb of penis21 Pampiniform venous plexus

A Left male pelvic viscera in sagittal section (from the right)B Left testicle (from the left)

Testes, seminal vesicles, prostate gland 115

A

B

20

19

5

21

3

41

2

17

618

10

10

9

5

87

12

13

14 11 16

15

S

AP

I

S

PA

I

Location of numbers: 1B; 2B; 3B; 4B; 5AB; 6A; 7A; 8A; 9A; 10A; 11A; 12A; 13A; 14A; 15A; 16A; 17A; 18A; 19A; 20A; 21B.

Bladder, female urethra, vagina

Bladder

The bladder (1) stores urine and lies anteriorly in thepelvis behind the pubic bones and symphysis (2). Ithas a triangular base or trigone (3), which in thefemale lies anterior to the upper vagina (4), uterinecervix (5) and pelvic floor (6). In the male, the trigonelies anterior to the seminal vesicles, rectum and pelvicfloor. The ureters (7,8) enter the posterolateral cor-ners of the trigone. The bladder wall is formed bydetrusor muscle and lined internally by transitionalepithelium, which allows distension. The tone in thedetrusor ‘pays out’ as the bladder fills.

The bladder base and neck (anterior end of trigone)– where the urethra (9) emerges – are fixed to theunderlying pelvic structures and pelvic fascia. The lat-ter thickens as pubovesical ligaments. The remainderof the bladder is free to ascend out of the pelvis andinto the abdomen (if it contains approximately500 mL), but always outside the peritoneum (10),immediately posterior to the anterior abdominal wall.The apex is continuous with the obliterated urachusthat may be visible as the median umbilical ligament.As the pelvis is a relatively small cavity the bladder isrelated to its lateral walls (levator ani and obturatorinternus), the branches of the internal iliac vessels, andthe pelvic plexus of nerves.

The bladder is supplied by the superior and inferiorvesical branches of the internal iliac artery (11) anddrains to the vesical plexus (around its base) thatdrains to the internal iliac veins. Lymph drainage is tothe iliac nodes. The nerve supply is derived from thelumbar splanchnic sympathetic nerves (L1,2) passingin the hypogastric nerves to the pelvic plexus, andfrom the parasympathetic sacral splanchnics (S2,3,4).Detrusor is controlled by the parasympathetics andthe smooth muscle of the trigone and bladder neck bythe sympathetics.

Female urethra

The female urethra transmits urine to the exterior. Itpasses through the pelvic floor to continue in the ante-

rior vaginal wall and is a closed slit, 4 cm long. Theshort urethra predisposes the female to urinary tract infec-tions, although the mucous membrane falls into folds thatcontact each other. Smooth muscle from the bladderneck descends longitudinally into the urethra to helppull it open during micturition. Other smooth musclefibres encircle the urethra providing a sphinctericeffect. But urinary continence is dependent on pres-sure from the surrounding pelvic organs on the blad-der neck and proximal urethra, before it passesthrough the pelvic floor. If the bladder drops and theurethra is below the pelvic floor, continence may becompromised.

Vagina

The vagina is a tube passing upward and backward,through the perineum and through the pubovaginalispart of levator ani, to receive the cervix just above thepelvic floor. The anterior and posterior walls areopposed to each other so the vagina is a narrow slit.The wall is of smooth muscle and the mucous mem-brane (stratified squamous epithelium) is folded sothat it may allow distension during intercourse andchildbirth.

As the cervix pushes into the vagina, the vaginal wallbulges around it causing small anterior and lateral for-nices and a larger posterior fornix. Care must be takenduring vaginal hysterectomy to avoid damage to theureters. The posterior fornix is distensible and may hideforeign bodies. It is also directly related to the peritoneumof the recto-uterine pouch (of Douglas) (17).

Within the urogenital diaphragm the urethra andthe vagina are encircled by the striated, external ure-thral sphincter, whose nerve supply is via perinealbranches of the pudendal nerve (S2,3,4). Sensorysupply of the urethra and vagina is also via thesenerves.

Blood supply to the vagina and urethra is by variablebranches from uterine, vaginal and internal pudendalbranches of the internal iliac artery. Venous drainageis via the vaginal plexus, draining to the internal iliacveins (20). Lymph drainage from the upper vaginaand urethra is to the iliac nodes and from the lower tothe superficial inguinal nodes.


1 Bladder2 Pubic symphysis3 Base of bladder4 Vagina5 Cervix of uterus

6 Cut edge of levator ani7 Left ureter (displaced anteriorly)8 Right ureter9 Urethra

10 Peritoneum

11 Internal iliac artery12 External iliac artery and vein13 Clitoris14 Anus15 Labium majus

16 Labium minus17 Recto-uterine pouch (of Douglas)18 Rectum19 Vesico-uterine pouch20 Internal iliac vein

A Left female pelvic viscera in sagittal section (from the right)

Bladder, female urethra, vagina 117

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Pelvic ureter, male urethra

The ureters

After entering the pelvis the ureters (1,2) lie antero-medial to branches of the internal iliac artery (3). Inthe female they lie posterior to the ovaries, beforepassing medially and anteriorly toward the bladderbase, inferior to the uterine arteries, just lateral to thevaginal lateral fornices. In the male the vas deferens(4) crosses above and anterior to the ureter. Theureters enter the posterolateral corners of the trigoneand pass obliquely through the bladder wall, creatinga flap-valve effect, to prevent urinary reflux.

The pelvic part of the ureter picks up its blood sup-ply and innervation from branches of the gonadal andvesical arteries. There is equivalent venous and lym-phatic drainage.

Male urethra

The urethra transports urine from the bladder (5) toits slit-like opening on the glans penis (6). As the neckof the bladder (7) opens into the urethra, it iscompletely surrounded by the prostate gland (8),and together they pass through the puboprostaticpart of levator ani (9). The prostate rests on the uro-genital diaphragm, but the urethra continues throughit.

The urethra is lubricated by mucous glands and alsoreceives the reproductive ducts, prostatic and ejacula-tory. It has prostatic (10), membranous (11) andpenile (12) parts that in total follow an S-shapedcourse: vertically downward through the prostate; for-ward through the membranous part; and eventuallydownward again in the penile part, when the penis isnot erect.

The prostatic urethra has a midline, longitudinalridge posteriorly, the urethral crest. The groove oneach side of this receives the opening of many prosta-tic ducts. Halfway down the crest there is a small

enlargement, the seminal colliculus or verumon-tanum. Here are the openings of the ejaculatory ductsand the utricle, a functionless embryological remnant.Normally the urethra is closed with its mucous mem-brane thrown into folds. The muscle of the bladderwall is continuous with the fibromuscular stroma ofthe prostate gland, and the muscle of the bladder neckcontinues into the prostatic urethra. Some fibres arelongitudinal, but most encircle the proximal urethra asthe internal (smooth muscle) urethral sphincter thatprevents the backflow of semen into the bladder dur-ing ejaculation (see p. 171).

The membranous urethra is the part passing throughthe urogenital diaphragm that contains the striatedmuscle of the external urethral sphincter (13), whichsurrounds the urethra and is supplied by perinealbranches of the pudendal nerve (S2,3,4). The urethrapasses through the bulb of the penis (14) and theninto its corpus spongiosum (15). In the bulb the ure-thra receives the bulbo-urethral ducts that carry lubri-cating mucus from the bulbo-urethral glands in theurogenital diaphragm. The bulb itself is surrounded bybulbospongiosus muscle that contracts to expel thelast drops of urine or semen.

The urethra reaches the glans, and dilates as the nav-icular fossa, before narrowing to its external opening.Small mucous glands open into the navicular fossa,and also appear as urethral lacunae along the penileurethra.

The same arteries that supply the prostate and penissupply the urethra (inferior vesical, artery to the bulb,dorsal artery of the penis). Its venous drainage is to theprostatic plexus and internal iliac vein (19). Lymphdrainage is to internal iliac nodes. Sensory nerve sup-ply is via the pudendal nerve (S2,3,4).

During urethral catheterization in the male, care mustbe taken to straighten the curves of the urethra manually.It is possible to rupture the urethra in its thinner mem -branous part, and also to create false passages throughthe prostate gland.


1 Left ureter2 Right ureter (distal end)3 Internal iliac artery4 Left vas (ductus) deferens5 Bladder6 Glans of penis

7 Neck of bladder8 Prostate gland9 Cut edge of levator ani

10 Prostatic urethra11 Membranous urethra12 Penile urethra

13 External urethral sphincter14 Bulb of penis15 Corpus spongiosum16 Corpus cavernosum17 Ureteric openings18 Pubic symphysis

19 Internal iliac vein20 External iliac artery and vein21 Inferior epigastric vessels

A Left male pelvic viscera in sagittal section (from the right)

Pelvic ureter, male urethra 119

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Rectum, anal canal

Rectum

The rectum (1) lies posteriorly within the pelvic cav-ity, following the concavity of the sacrum (2). It is thecontinuation of the sigmoid colon and holds faecesimmediately prior to evacuation. It is about 12 cmlong, starts at S3, and becomes wider inferiorly, dilat-ing as the rectal ampulla. It takes a sinuous course ofleft, right, left curves. The sigmoid enters it from theleft, creating a concavity to the left at the start of therectum. The middle concavity is on the opposite side,the right, and there is a smaller, less consistent concav-ity, again to the left, at the lower end of the rectalampulla, just above the anorectal junction. At the con-cavities the rectal wall tends to push into the lumen creat-ing three ‘shelves’ or rectal valves (of Houston) that maybe palpable on rectal examination and visible on proc-toscopy and sigmoidoscopy. The middle, right-sided‘shelf’ is the most prominent.

As it passes through the puborectalis part of levatorani (3) it turns sharply downward and backward as the4 cm long anal canal (4), which is for the evacuationof faeces.

Anal canal

The anal canal, which is entirely in the perineum, hasits mucous membrane raised into between five and tenanal columns (of Morgagni) by the underlying termi-nal branches of the superior rectal artery and vein.These columns end about half-way down the canal,and folds of epithelium, the anal valves, link theirlower ends. The lubricating, anal mucous glands openinto the anal sinuses between the columns, above andbehind the anal valves. Following years of wear andtear, these features may be difficult to distinguish inthe elderly.

The line of anal valves is the dentate or pectinateline, and it represents the change in embryologicaldevelopment from entoderm to ectoderm. There areother significant changes at the pectinate line. Above it,the mucous membrane is columnar and below it isstratified squamous. Above the line the innervation is

autonomic, sensitive to distension but not to pain, and ableto distinguish between flatus and faeces. Below the line theinnervation is somatic and the anal canal is sensitive topainful stimuli, such as ulceration, fissures or injections.

For about 1.5 cm below the pectinate line the thinstratified squamous epithelium covers the pecten thatends at an indistinct white line which overlies theintersphincteric groove, where the internal analsphincter ends. At the white line the stratified squa-mous epithelium begins to develop the features of skin(sweat glands, keratinization, hair follicles) and soonbecomes the anus. During defecation the anal canalopens and everts onto the surface as far as the pecten.

The mucous membrane of the anal canal is folded toallow distension during defecation. On proctoscopy itbulges into the proctoscope as anal cushions, usually atthe positions of three, seven and eleven on a clock face.In a similar way the mucous membrane may bulge (pos-sibly caused by distended submucosal veins) into anddown the anal canal, as piles or haemorrhoids, which mayremain outside the anus. Bleeding from the capillaries ofthis mucous membrane is known as bleeding haemor-rhoids.

Blood supply to the rectum and anal canal is via thesuperior rectal branches of the inferior mesentericartery, the variable middle rectal branch of the inter-nal iliac (8), and the inferior rectal branch of theinternal pudendal. There is free anastomosis betweenall these vessels. The venous drainage is via a similarroute, returning via the superior rectal veins, to infe-rior mesenteric and portal vein or via the internal iliacvein (10) (portosystemic anastomosis).

Lymph drainage is to the sacral and iliac nodes, butthe upper rectum drains to the inferior mesentericnodes, and the lower anal canal to the superficialinguinal nodes. Innervation is via the autonomic sys-tem or via the inferior rectal branch of the pudendalnerve. Parasympathetic afferents return to S2–S4,from which the pudendal nerve arises, allowing theimportant reflexes between the autonomic andsomatic systems (see p. 170).

During rectal (digital) examination in the male theprostate gland (11) can be assessed, but the seminalvesicles (15) are only palpable if they are abnormal.


1 Rectum2 Sacrum3 Cut edge of levator ani4 Anus (lower end of anal canal)5 External anal sphincter

6 Left ureter7 Right ureter (distal end)8 Internal iliac artery9 Left vas (ductus) deferens

10 Internal iliac vein

11 Prostate gland12 Obturator nerve13 Bladder14 Pubic symphysis15 Left seminal vesicle

16 Rectovesical fascia17 Neck of bladder18 Coccyx19 External iliac artery and vein

A Left male pelvic viscera in sagittal section (from the right)

Rectum, anal canal 121

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Ovary, uterine tubes

Ovary

During reproductive life, under the control of thepituitary gland, the ovary (1) secretes the female sexhormones, oestrogen and progesterone, as well asmonthly, the ovum.

In the adult female, the ovary is oval in shape andabout the size of the terminal phalanx of the thumb.It is suspended by a short mesovarium from the poste-rior leaf of the broad ligament (2), and lies in a fossaon the lateral pelvic wall with the ureter (4) posteri-orly and the obturator nerve laterally. Consequently,great care must be taken during ovarian surgery to avoiddamaging the ureter. Inflammatory conditions of theovary may irritate the obturator nerve and cause pain tobe referred to the medial thigh. In elderly women theovary is usually shrunken. During pregnancy it is liftedout of the pelvis and may return to lie in variable posi-tions within the pelvis.

The ovary brings its blood and nerve supply with itfrom its initial position on the posterior abdominalwall. The ovarian artery (5) leaves the aorta at thelevel of L2, passes down the posterior abdominal walland into the suspensory ligament of the ovary (6),before reaching the ovary in its mesovarium. Venousdrainage is via a plexus of veins that accompany theartery and eventually coalesce to form the ovarianvein. The right ovarian vein drains to the inferior venacava, the left ovarian vein to the left renal vein. Lymphdrainage is to the para-aortic nodes.

Sympathetic innervation, with its accompanyingafferents, is derived from the lesser splanchnic nerves(T10,11). Therefore, ovarian (visceral) pain may refer tothe T10,11 dermatomes, in the midline, the peri-umbili-cal region (as well as to the medial thigh via the obturatornerve).

During development, the peritoneum overlying theovary is said to become incorporated into its wall,therefore, the ovary is the only truly intraperitonealstructure. At ovulation the ovum is secreted into theperitoneal cavity, to be ‘picked up’ by the uterinetube. Rarely, but dangerously, it is possible for the ovumto be fertilized, and then implant and develop as anectopic pregnancy in the peritoneal cavity (see pp. 169and 170).

Uterine (Fallopian) tubes

The uterine tubes (7) emerge from each side of theuterus to lie in the upper free edge of the broad liga-ment. The part of the broad ligament that acts as amesentery for the tube is called the mesosalpinx.Sperm entering the vagina pass through the cavity ofthe uterus and into the uterine tube, where fertiliza-tion of the ovum occurs. The fertilized ovum is thentransported down the tube to implant and developwithin the uterus. Should such transport not occur thefertilized ovum might develop in the tube as an ectopic,tubal pregnancy.

Medially, the uterine tube has an intramural part,within the wall of the uterus. Moving laterally it has anisthmus, ampulla, infundibulum (8), and finally asplayed, fimbriated end (9). The infundibulumpierces the posterior leaf of the broad ligament so thatthe fimbriae overhang the ovary in the peritoneal cav-ity. One fimbria usually attaches to the ovary.

The tube receives blood supply via an anastomosisbetween the ovarian and uterine arteries. Venousdrainage is to the ovarian and uterine veins. Lymphdrainage is to the para-aortic nodes.

The afferent nerve supply returns to the T11,12 andL1 segments of the cord. Consequently, tubal pain islower abdominal but may extend to the iliac fossa and, ifon the right, may confuse the diagnosis of appendicitis.


1 Ovary2 Posterior leaf of broad ligament3 Anterior leaf of broad ligament4 Left ureter5 Ovarian artery

6 Suspensory ligament of ovary7 Uterine tube8 Infundibulum of uterine tube9 Fimbriated end of uterine tube

10 External iliac artery and vein

11 Internal iliac artery12 Psoas major13 Bladder14 Fundus of uterus15 Rectum

16 Vesico-uterine pouch17 Recto-uterine pouch (of Douglas)

A Female pelvic contents (from the front)B Left ovary (from behind)

Ovary, uterine tubes 123

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Location of numbers: 1AB; 2B; 3A; 4A; 5A; 6A; 7A; 8B; 9AB; 10A; 11A; 12A; 13A; 14A; 15A; 16A; 17A.

Uterus, cervix

Uterus

The uterus (1) is a single organ in the midline (orslightly deviated from it) of the female pelvis. Its cav-ity is for the implantation and development of theembryo and its placenta. Normally the uterus is aboutthe size and shape of a medium pear, but during preg-nancy it hugely increases in size. It has a fundus (abovethe entry of the uterine tubes), a body and a cervix.

The uterine wall is muscular so that it can relax andexpand during pregnancy but contract during labour.The mucous lining (endometrium) is controlled by thecyclical ovarian hormones, the mucosa being preparedeach month for implantation of the fertilized ovumbut shed at menstruation if that does not occur.

Cervix

The cervix (2) is a small cylinder with a very narrowlumen that is effectively occluded by its interdigitatingfolds of mucous membrane. Motile sperm swim theirway through. The cervix pushes into the anterior wallof the vagina, therefore has vaginal and supravaginalparts. Normally it meets the vagina (3) at right angles,the anteverted position. Where the body of the uterusand the cervix meet, the body is tilted forward in theanteflexed position. This combination of anteversionand anteflexion means the uterus has an antero-inferior surface related to the bladder and a postero -superior surface related to coils of intestine. The cervixand vagina meet each other low down in the pelviccavity, just superior to the pelvic floor (4) and in frontof the rectum (5). Cervical dilatation during the earlystages of labour may be assessed by rectal examination.

It is important that the uterus is maintained in itsnormal anatomical position and there are a multitudeof factors to uterine support. The surrounding organs,all closely fitted into the pelvic cavity, support each

other. The muscular pelvic floor and the integrity ofthe perineal body (6) are essential. The pelvic floorfascia thickens around the uterine arteries as lateralligaments. Other fascial thickenings pass from theuterus to the sacrum (uterosacral) and from the cervixto the pubis (pubocervical). The broad (8) and round(9) ligaments maintain anteversion and anteflexion.

Repeated pregnancy may weaken the supports allow-ing ‘slippage’ of the uterus and vagina. This may well alterthe position of the bladder to cause poor urinary control,stress or urge incontinence and urinary infections. Inmore extreme situations rectal continence may beaffected, and the uterus may prolapse into the vagina andeven descend to appear externally. Disruption of antever-sion and anteflexion may cause backache and difficulty inconception.

The uterus is supplied by the uterine arteries, whichare branches of the internal iliac arteries (10). Theseanastomose freely with each other and with theovarian arteries, which tend to supply the fundus.Consequently, venous drainage is mainly to the inter-nal iliac veins (13), but to the ovarian veins (14) aswell. As the uterine arteries pass along the pelvic floorto the lateral aspect of the uterus, they pass above theureter (15,16), just lateral to the cervix and the lateralvaginal fornices. During surgery great care must betaken not to damage the ureter.

Lymph drainage of the fundus tends to follow theovarian artery to the para-aortic nodes. But the bodyand cervix drain to sacral and iliac nodes, usually theexternal iliac. Some lymph drainage may follow theround ligament to the superficial inguinal nodes.

Nerve supply is via the pelvic plexus containing bothsympathetic (T10–12 and L1) and parasympathetic(S2–4) components. Afferents from the body and fun-dus are thought to pass with the sympathetics so that painis lower abdominal. But those of the cervix are thought topass with the parasympathetics giving rise to deep pelvicpain.


1 Body of uterus2 Cervix of uterus3 Vagina4 Cut edge of levator ani (pelvic

floor)5 Rectum6 Perineal body (central perineal

tendon)

7 Bladder8 Broad ligament9 Round ligament

10 Internal iliac artery11 Clitoris12 External iliac artery and vein13 Internal iliac vein14 Ovarian artery and vein

15 Right ureter16 Left ureter17 Ovary18 Uterine (Fallopian) tube19 Recto-uterine pouch (of Douglas)20 Vesico-uterine pouch21 Pubic symphysis22 Anus

23 External anal sphincter24 Labium majus25 Labium minus26 Urethra

A Left female pelvic viscera in sagittal section (from the right)

Uterus, cervix 125

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The Torso

Part VII

55 The torso 128

The torso

Upper body and thorax

Any movement at the shoulder joint is accompaniedby movements of the pectoral girdle (scapula and clav-icle). Muscles arise from the torso and skull to attachto the clavicle (1), scapula and humerus. The scapulamay be:● rotated upward during abduction by trapezius (2),

serratus anterior (3)● rotated downward during adduction by pectoralis

major (4,5) and minor (9), latissimus dorsi (10)● protracted by pectoralis major and minor, serratus

anterior● retracted by rhomboids (11), trapezius, levator

scapulae.The muscles combine to brace the scapula against thethoracic wall and hold its position to provide a plat-form for the upper limb when carrying weights orpushing. Many are accessory muscles of respiration.Anterior muscles that attach to the humerus flex theshoulder joint, posterior muscles extend it.● Trapezius (accessory (XI)) – from skull, cervical

spines via ligamentum nuchae and thoracic spinesto scapular spine, acromion process, and lateral one-third of clavicle (posterior aspect).

● Serratus anterior (long thoracic (C5,6,7)) – fromupper eight ribs to medial border and inferior angleof scapula. Injury to the long thoracic nerve allows‘winging’ of the scapula and full arm abduction as inbrushing one’s hair is difficult.

● Pectoralis major (pectoral (C5–8)) – frommanubrium, sternum, upper six costal cartilages,and medial clavicle to anterior lip of intertuberculargroove of humerus.

● Pectoralis minor (pectoral (C5–8)) – from the third,fourth and fifth ribs to coracoid process of scapula.

● Latissimus dorsi (thoracodorsal (C6,7,8)) – fromilium, thoracolumbar fascia (12), lower four ribsand inferior angle of scapula to floor of intertuber-cular groove, after winding around teres major (13).

● Rhomboid major and minor (dorsal scapular C 5) –from the spines of C7–T5 to medial border ofscapula.

● The triangle of auscultation (14) is between thescapula, trapezius and latissimus dorsi.

● Deltoid (15) (axillary (C5,6)) – from scapularspine, acromion process and lateral one-third clavi-cle (anterior aspect) to mid-shaft humerus, lateralaspect. Muscle fibres lie anterior to, posterior to,and over the shoulder joint. Therefore, deltoidflexes, extends and abducts.

Abdomen

Muscles of the abdominal wall support the abdominalcontents and the vertebral column.

Rectus abdominis (16) (segmental T7–12) flexesthe trunk. It lies on either side adjacent to the midline.It passes from the costal cartilages of the fifth to sev-enth ribs to the pubic crest (17) and symphysis (18).It is partially divided by three transverse tendinousintersections (19). On a slim subject the muscle inbetween the intersections may form visible bulges onthe anterior abdomen.

Each rectus abdominis lies within a rectus sheath(20) created by the aponeuroses of external oblique(21), internal oblique and transversus abdominis. Thetendinous intersections fuse with the anterior layer ofthe sheath, but not its posterior layer. External obliqueis superficial, therefore forms the anterior layer of thesheath. The aponeurosis of internal oblique (thedeeper muscle layer) splits to enclose rectus abdo-minis, contributing to both the anterior and posteriorlayers of the sheath. Transversus abdominis is thedeepest layer and its aponeurosis forms the posteriorlayer of the sheath.

At a variable distance, but usually just a few cen-timetres below the umbilicus, the posterior rectussheath stops and all the aponeuroses pass anterior torectus abdominis. The end of the posterior sheath isthe arcuate line (of Douglas) and the inferior epigas-tric artery and vein enter the sheath here.

In the midline these aponeuroses all fuse to form therelatively avascular linea alba (22). Its position is seen asthe vertical midline groove in the living abdomen. Thelateral edge of rectus abdominis is visible as the lineasemilunaris. The umbilicus (25), in the midline, liesopposite L3/L4 in a slim, fit subject, but indicates theT10,11 dermatomes.

128 The Torso

1 Clavicle2 Trapezius3 Serratus anterior4 Clavicular part of pectoralis

major5 Sternocostal part of pectoralis

major

6 Manubrium7 Body of sternum8 Xiphoid process9 Pectoralis minor

10 Latissimus dorsi11 Rhomboids (major and minor)12 Thoracolumbar fascia

13 Teres major14 Triangle of auscultation15 Deltoid16 Rectus abdominis17 Position of pubic crest18 Pubic symphysis19 Tendinous intersection

20 Rectus sheath21 External oblique22 Linea alba23 Erector spinae24 Gluteus maximus25 Umbilicus

A Anterior muscles of the torso (from the front)B Posterior muscles of the torso (from behind)

The torso 129

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Location of numbers: 1A; 2B; 3A; 4A; 5A; 6A; 7A; 8A; 9A; 10B; 11B; 12B; 13B; 14B; 15AB; 16A; 17A; 18A; 19A; 20A; 21A; 22A; 23B; 24B; 25A.


The UpperLimb

Part VIII

56 Axilla, upper limb fascia, veins, arteries 13257 Shoulder (glenohumeral) joint 13458 Elbow, superior radio-ulnar, inferior

radio-ulnar, wrist and mid-carpal joints 13659 Upper limb: anterior muscle groups 13860 Upper limb: posterior muscle groups 14061 Superficial palm of hand, median nerve 14262 Deep palm, ulnar nerve, arteries 14463 Axillary artery, brachial plexus, radial

nerve 146

Axilla, upper limb fascia, veins,arteries

Axilla

The axilla is inferior to the shoulder joint and filled withfat, lymph nodes and the neurovascular supply for theupper limb. Its apex is bounded by the first rib, scapulaand clavicle (1), and through it structures pass betweenthe root of the neck and the upper limb. Serratus ante-rior (5), the ribs and intercostal muscles lie medially.The intertubercular groove of the humerus lies laterally.Subscapularis forms the posterior wall. Immediatelyinferior to it, latissimus dorsi (6) and teres major arepalpable as the posterior axillary fold. Pectoralis major(7,8) and minor (9) form the anterior wall, with theinferior edge of major palpable as the anterior axillaryfold. The axillary lymph nodes (12) drain the upperlimb, but more importantly in the female, they drainmuch of the breast. The nodes are arranged as follows:● A – anterior (pectoral) behind pectoralis minor,

draining breast and anterior body wall aboveumbilicus

● P – posterior (subscapular) on subscapularis, drain-ing posterior body wall above umbilicus

● I – infraclavicular● C – central● A – apical● L – lateral, around axillary vein, draining upper limb.The anterior, posterior and lateral groups drain to thecentral group that, along with the infraclaviculargroup, drains to the apical nodes. Afferents from thelatter communicate with the deep cervical nodes anddrain to the subclavian lymph trunk. Individual groupsare usually indistinguishable in a normal cadaveric dis-section. But they are significant in staging the spread ofbreast tumours. The communication between axillary anddeep cervical lymph nodes means that breast tumoursmay spread to the latter.

Upper limb fascia

The upper limb has a thin sleeve of deep fascia (13)that attaches to palpable bony prominences (spine ofscapula, acromion, clavicle, humeral epicondyles andsubcutaneous border of ulna). It gives origin to mus-cles and sends septa between muscle groups to formcompartments in which the muscles move in relation

to each other and to the overlying skin. The compart-ments may limit swelling following crush injuries orfractures. The resultant pressure (compartment syn-drome) may compress the nerves and blood vesselswithin the compartments and cause muscle ischaemiawith consequent necrosis and (Volkmann’s) contracture.Distally the fascia specializes as extensor and flexorretinacula (14), and the palmar aponeurosis (15).

Veins

The veins have valves to prevent backflow. The deepveins commence as venae comitantes of the arteries,but converge on the axillary vein (16), as do the super-ficial veins. The veins draining the fingers and handpass dorsally to form the dorsal carpal plexus, whichlaterally becomes the cephalic vein (17) and mediallythe basilic vein. Both are visible under the skin, alongwith many other, variable veins.

The cephalic vein passes proximally up the radialborder of the forearm to the elbow, then lateral tobiceps (18) before running in the groove between pec-toralis major and deltoid (22). At the upper end ofthis groove it pierces the fascia to enter the axillaryvein. At the wrist, the cephalic is in a constant positionand may be used as a site of ‘cutting down’ through theskin to locate the vein for emergency, rapid access.

The basilic vein passes proximally on the ulnar bor-der of the forearm to the elbow, and then medial tobiceps before piercing the deep fascia half way up thearm to join the venae comitantes of the brachial arteryand become the axillary vein. Anterior to the elbowthe cephalic and basilic veins are connected by themedian cubital vein (23), passing medially and superi-orly. It usually receives the median vein of the forearmand lies anterior to the brachial artery (24) andmedian nerve (25), but separated from them by thebicipital aponeurosis (26).

Arteries

Arteries are palpable as pulses when they lie superfi-cially, but may also be compressed against bone.Medial to the tendon of biceps the brachial pulse ispalpable at the extended elbow. Proximal to the baseof the thumb, lateral to flexor carpi radialis (29), theradial pulse (30) is palpable at the wrist. Arterial vari-ation is common and the brachial artery or its branchesmay take a course superficial to the aponeurosis.

132 The Upper Limb

A

B

C

2

3

19

1 16 9 22

8

4

6 24

1825

17

27

13

29

30

25

28

14

15

23

26

7

22

17

7/8

6

18

5

21 12

9

8

11

10 20

4

S

LR

I

Prox

Lat(L)

M

D

Prox

Lat(Rad)

M(UL)

D

1 Clavicle2 Investing layer of deep cervical

fascia3 Platysma4 Sternal head of

sternocleidomastoid5 Serratus anterior6 Latissimus dorsi7 Clavicular part of pectoralis major

8 Sternocostal part of pectoralismajor

9 Pectoralis minor10 Manubrium11 Sternum12 Axillary lymph nodes13 Deep fascia of forearm14 Flexor retinaculum15 Palmar aponeurosis

16 Axillary vein17 Cephalic vein18 Biceps19 Acromioclavicular joint20 Sternoclavicular joint21 Thoraco-acromial vessels and

lateral pectoral nerve22 Deltoid23 Median cubital vein

24 Brachial artery25 Median nerve26 Bicipital aponeurosis27 Superficial subcutaneous tissue28 Ulnar artery29 Flexor carpi radialis30 Radial artery

A Left shoulder, superficial structures(from the left)

B Left upper limb, superficial structures(from the front)

C Left forearm and hand, superficialstructures (from the front)

Axilla, upper limb fascia, veins, arteries 133

Location of numbers: 1A; 2A; 3A; 4AB; 5A; 6AB; 7A; 8AB; 9AB; 10A; 11A; 12A; 13C; 14C; 15C; 16A; 17AB; 18AB; 19A; 20A; 21A; 22AB; 23B; 24B;25BC; 26B; 27C; 28C; 29C; 30C.

Shoulder (glenohumeral) joint

Any movement at the shoulder joint is accompaniedby movements of the pectoral girdle. (See section ontorso, p. 128).

The shoulder is a typical synovial, ball and socketjoint between the scapular glenoid fossa (2) and therelatively larger humeral head (3). The fibrocartilagi-nous glenoid labrum (4) deepens the fossa. The jointcapsule is lax, sacrificing stability for mobility. Itattaches to the scapula and glenoid labrum, and to theanatomical neck of the humerus. Medially the capsuledips down the shaft of the humerus to provide extraspace for the humeral head during abduction. Itmaybe minimally strengthened by glenohumeral liga-ments anteriorly and a coracohumeral ligament supe-riorly.

To provide support and stability, the acromial andcoracoid processes overhang the joint, as does thecoraco-acromial ligament that connects the twoprocesses. The tendon of the long head of biceps lieswithin the shoulder joint and attaches to the supragle-noid tubercle of the scapula, immediately above theglenoid fossa. The long head of triceps (6) attachesto the infraglenoid tubercle, immediately inferior tothe fossa, and provides some support for the joint infe-riorly. The bones are held in close apposition by sur-face tension within the joint. But most of the stabilityis dependent on the musculotendinous, rotator cuffformed by four muscles arising from the scapula andinserting into the humerus, very close to its head, andinto the shoulder joint capsule itself. By virtue of theirdual insertions they stabilize the shoulder joint, hold-ing the humeral head against the glenoid.

Shoulder movements

● Abduction – supraspinatus (7) (suprascapularnerve (C5,6)) passes from the supraspinous fossa ofthe scapula to the upper facet on the greatertuberosity of the humerus (8). Passing above thejoint it initiates abduction.

● External (lateral) rotation – infraspinatus (supras-capular nerve (C5,6)) arises from the posterioraspect of the scapula. Teres minor (9) (axillarynerve (10) (C5,6)) arises from the lateral border of

the scapula. Both muscles pass posterior to the joint(to the greater tuberosity) therefore must externallyrotate it.

● Internal (medial) rotation – subscapularis (12)(nerves to subscapularis (C5,6,7) from the posteriorcord of the brachial plexus) passes from the anterioraspect of the scapula to the lesser tuberosity of thehumerus. As it lies anterior to the joint it mustinternally rotate it.

● Adduction – teres major (13) (lower subscapularnerve (C6,7)) is not part of the musculotendinouscuff as it passes from the inferior angle of thescapula to the posterior lip of the intertuberculargroove. It adducts the humerus and as its insertionis in a plane anterior to the shoulder joint it alsointernally rotates it.The shoulder joint is a common cause of complaint.

Supraspinatus tendon passes in the coraco-acromialbursa, between the upper aspect of the joint capsule andthe coraco-acromial ligament. The tendon may becomeinflamed causing pain during the phase of abductionwhere it passes beneath the ligament. The tendon mayrupture. Subscapularis and infraspinatus also have bursaebetween their tendons and the joint capsule. All threebursae may communicate with the joint and all three maybecome painfully inflamed.

The shoulder is weakest at its inferior aspect. Excessive,forced abduction may cause the humeral head to dis -locate antero-inferiorly, where it may impinge on theaxillary nerve (C5,6) as it winds, with the posteriorcircumflex vessels (14), around the surgical neck of thehumerus, immediately inferior to the joint. Such damagemay cause paralysis of deltoid (15) and of teres minor.But the important test is for sensory loss over the skin ofthe lateral arm, the ‘regimental patch’. The axillary nerveis also at risk in fractures of the surgical neck of thehumerus. The brachial plexus passes from the neck to theupper limb, behind the clavicle. Shoulder dislocation maycause traction injury to the plexus.

To prevent vascular obstruction during joint move-ments, the arteries proximal to, and distal to jointssend branches that anastomose with each other andprovide collateral circulations. At the shoulder, thereis a rich scapular anastomosis between branches of thesubclavian and axillary arteries.

134 The Upper Limb

1 Scapula2 Glenoid fossa of scapula3 Head of humerus4 Glenoid labrum5 Clavicle

6 Long head of triceps7 Supraspinatus8 Greater tuberosity of humerus9 Teres minor

10 Axillary nerve

11 Shaft of humerus12 Subscapularis13 Teres major14 Posterior circumflex artery and

vein

15 Deltoid16 Tendon of latissimus dorsi17 Cavity of shoulder joint

A Coronal section through the left shoulder joint (from thefront)

Shoulder (glenohumeral) joint 135

A

155

7

17 32

8

15

1113

1

12

9 16

614

4

10

Prox

LatM

D

Line diagram adapted from Ellis H, Logan BM, Dixon AK (2001)Human Sectional Anatomy. London: Arnold.

Elbow, superior radio-ulnar,inferior radio-ulnar, wrist andmid-carpal joints

Elbow and superior radio-ulnar joint

The elbow and superior radio-ulnar joints may be con-sidered as one, as they share the same fibrous and syn-ovial joint capsules. Movements of the joint are flexionand extension, plus pronation and supination as theradius rotates around the ulna.

The radius and ulna are held together by theinterosseous membrane. The concave radial head (1)lies against the capitulum of the humerus (2), and isclasped to the ulna (3) by the anular ligament (4).The olecranon and coronoid processes of the ulnaform a hook that hangs onto the olecranon fossa,trochlear surface (5) and coronoid fossa of thehumerus.

The fibrous joint capsule is lax anteriorly and poste-riorly to allow flexion and extension, and it attaches atthe articular margins of the humerus and ulna. It doesnot attach to the radius but to the anular ligament.The olecranon, coronoid and radial fossae are includedwithin the capsule so that the equivalent processes ofthe ulna and radius may enter the fossae during appro-priate movements. Each fossa has a small pad of fatbetween the bone and the synovial membrane.

The capsule is thickened by collateral ligaments. Thelateral collateral ligament runs from the lateralhumeral epicondyle to the anular ligament and themedial collateral ligament is a triangular ligament withits apex at the medial epicondyle (6), and diverging tothe coronoid and olecranon processes of the ulna. Thecapsule may be pulled out of the way during elbowflexion by a few fibres of brachialis anteriorly, and dur-ing extension by triceps posteriorly. There is a subcu-taneous bursa over the olecranon as well as bursaesuperficial to, and deep to the triceps tendon. Thesebursae may become inflamed, as may the tendinous ori-gins at the medial and lateral epicondyles (the commonflexor and common extensor origins).

The median nerve and brachial artery lie anterior to

brachialis, itself anterior to the elbow. The ulnar nerve(7) lies posterior to the medial epicondyle. The radialnerve lies deep to brachioradialis (8), lateral to thejoint. All these structures are at risk of injury in fracturesand dislocations of the elbow. The radial head may acci-dentally be pulled out of the anular ligament, this usuallyoccurs when children are swung around by their arms.

Inferior radio-ulnar joint

The inferior radio-ulnar joint (13), is supported by theinterosseous membrane and by a triangular fibrocarti-lage disc (14) with its apex attached to the ulnar sty-loid, and its base attached to the radius (15).Consequently the disc, which moves with the radiusin pronation and supination, overlies the head of theulna (16), preventing the ulna from taking part in thewrist joint.

Wrist joint

The wrist joint itself is between the scaphoid (17),lunate (18) and radius. The hand is carried with theradius during pronation and supination. Forces passingthrough the hand are transmitted mainly via thescaphoid to the radius. The wrist may flex or extendand deviate in radial or ulnar directions. These move-ments involve adjunct movements at the mid-carpaljoint, between the proximal and distal rows of carpalbones. Although both joints are involved, extension isprimarily a wrist joint movement whereas flexion isprimarily at the mid-carpal joint.

Distally, the radius, ulna and carpal bones are boundtogether by a fibrous capsule, strengthened by manyligaments, named by their position and by the bones towhich they attach. A fall on the outstretched hand, in ayounger person usually causes fracture of the scaphoidwith tenderness in the anatomical snuffbox (26). Bloodsupply to the scaphoid passes from distal to proximal. Anundiagnosed/untreated scaphoid fracture may lead toavascular necrosis of the proximal fragment, and conse-quent early onset of wrist arthritis. A fall on the out-stretched hand in an elderly person is more likely to causea Colles’ fracture at the lower end of the radius.

136 The Upper Limb

A Coronal section through the left elbow joint (from thefront)

B Coronal section through the left hand and wrist joint(from behind)

C Sagittal section through the joints of the left wrist andmiddle finger (from the left)

1 Head of radius2 Capitulum of humerus3 Coronoid process of ulna4 Anular ligament5 Trochlea of humerus6 Medial epicondyle of humerus7 Ulnar nerve8 Brachioradialis9 Medial head of triceps

10 Extensor carpi radialis brevis11 Extensor carpi radialis longus12 Flexor carpi ulnaris

13 Inferior radio-ulnar joint14 Articular disc (triangular

fibrocartilaginous complex(TFCC))

15 Distal end of radius16 Head of ulna17 Scaphoid18 Lunate19 Triquetral20 Hamate21 Capitate22 Trapezoid

23 Trapezium24 Base of fifth metacarpal bone25 Third metacarpal bone26 Radial artery in anatomical

snuffbox27 Tendon of flexor digitorum

superficialis28 Tendon of flexor digitorum

profundus29 Adductor pollicis30 Abductor digiti minimi31 Second lumbrical

32 Pronator quadratus33 Flexor digitorum profundus34 Shaft of radius35 Shaft of ulna36 Flexor digiti minimi brevis37 Extensor digitorum38 Flexor retinaculum39 Palmar aponeurosis40 Capsule of wrist joint

Elbow and forearm joints 137

A B C

9

65

2 8

3036

24

20

29

2322 26 2729

28

25

21

18

15

37

34

32

33

40

38

39

17

1513

32

16

35

34

19

14 18

21

31

28

4

11

1034

33

127

3 1

9

D

LatM

Prox

D

PalDor

Prox

Prox

LatM

D

Location of numbers: 1A; 2A; 3A; 4A; 5A; 6A; 7A; 8A; 9A; 10A; 11A; 12A; 13B; 14B; 15BC; 16B; 17B; 18BC; 19B; 20B; 21BC; 22B; 23B; 24B; 25C; 26B;27C; 28BC; 29BC; 30B; 31B; 32BC; 33AC; 34ABC; 35B; 36B; 37C; 38C; 39C; 40C.

Line diagrams adapted from Ellis H, Logan BM, Dixon AK (2001) Human Sectional Anatomy. London: Arnold.

Upper limb: anterior musclegroups

Elbow flexion and supination

The anterior compartment of the arm has coraco-brachialis (4), a shoulder adductor, medially withbrachialis and biceps anteriorly. Brachialis passes fromthe humerus to the ulna and flexes the elbow. Biceps(5) has a short head (6) from the coracoid process anda long head (7) from the supraglenoid tubercle of thescapula. Both heads converge on a tendon (8) thatinserts into the radial (bicipital) tuberosity, and alsointo the bicipital aponeurosis (9), which merges withthe deep fascia to attach to the ulna. Biceps is a pow-erful flexor and supinator. The musculocutaneousnerve (11) (C5,6,7) supplies all three muscles beforebecoming the lateral cutaneous nerve of the forearm.

In the forearm, the muscles are divided into deepand superficial groups. Their actions are: pronation;wrist (carpal) flexion, including radial or ulnar devia-tion; finger flexion; thumb flexion. In general, thesuperficial group arise from the common flexor origin(CFO) on the anterior aspect of the medial epicondyleof the humerus, as well as from adjacent bone andfascia.

Pronation

Pronator teres arises by two heads (the median nerve(12)) passing between, and therefore supplying them)from the CFO and the ulna. It passes to the convexityof the mid-shaft of the radius to roll it over the ulna inpronation. Pronator quadratus (13) is deeply and dis-tally situated, passing between the anterior aspects ofradius and ulna. It pronates as well as holding theradius and ulna in pronation. The anterior interosseousbranch of the median nerve supplies them both, teres(C6,7) and quadratus (C8,T1).

Wrist flexion

Flexor carpi radialis (17) and flexor carpi ulnaris (18)arise from the CFO, but ulnaris also has a large ulnarhead (the ulnar nerve (19) passes between the twoheads of ulnaris and supplies them). Radialis passesposterior to the flexor retinaculum to attach to thebases of the second and third metacarpals, whereasulnaris attaches via the pisiform to the hamate and

fifth metacarpal. Both flex the wrist but add radial orulnar deviation, respectively. Palmaris longus (20)arises from the CFO and attaches to the flexor retinac-ulum and palmar aponeurosis to flex the wrist.

Flexor carpi ulnaris is supplied by the ulnar nerve(C8,T1), and the other two by the median nerve(C6,7,8). At the wrist the tendon of flexor carpi radi-alis has the median nerve medially and the radialartery (21) laterally.

Finger (digit) flexion

Flexor digitorum superficialis (22) arises from theCFO as well as the ulna, radius and overlying fascia.Flexor digitorum profundus (23) arises from the ulnaand interosseous membrane. The tendons pass, in asynovial sheath, posterior to the flexor retinaculum(carpal tunnel) and into fibrous sheaths (24) anteriorto the digits. Superficialis splits to attach to each sideof the middle phalanges. Profundus passes through thesplit to attach to the base of the distal phalanges and isthe only muscle to flex the distal interphalangealjoints. The muscles normally function together, to rollthe fingers into flexion. But they must be tested individ-ually when assessing injury. Holding three of a patient’sfingers in extension prevents movement by profundus.Active flexion of the remaining finger is then only possi-ble at the proximal interphalangeal joint and tests super-ficialis. Each finger must be assessed in turn. Active flexionof the distal interphalangeal joints individually tests pro-fundus.

Superficialis is supplied by the median nerve, andprofundus by the median for index and middle fingerand the ulnar for ring and little fingers, i.e. the ulnarside of hand (C7,8,T1).

Thumb flexion

Flexor pollicis longus (26) from the radius andinterosseous membrane passes posterior to the flexorretinaculum then, in fibrous and synovial sheaths, toinsert onto the base of the distal phalanx. Assisted byflexor pollicis brevis (27), it flexes the thumb and issupplied by the median nerve (anterior interosseousbranch) (C8,T1).

For the thumb and little finger the synovial sheathsin the digits are continuous with that in the carpal tun-nel. This communication facilitates the spread of infectioninto the hand.

138 The Upper Limb

A B

32

1

2

11

4

6

531

1910

26

13

17

25

2729

28

30

24

23

15

16

141720

22

1821

812

9

7

Prox

LatM

D

Prox

Lat(Rad)

M(UL)

D

1 Pectoralis major2 Pectoralis minor3 Deltoid4 Coracobrachialis5 Biceps6 Short head of biceps, fused with

coracobrachialis7 Long head of biceps8 Tendon of biceps9 Bicipital aponeurosis

10 Brachial artery11 Musculocutaneous nerve12 Median nerve13 Pronator quadratus14 Cephalic vein15 Brachioradialis16 Extensor carpi radialis longus17 Flexor carpi radialis18 Flexor carpi ulnaris19 Ulnar nerve

20 Palmaris longus21 Radial artery22 Flexor digitorum superficialis23 Tendons of flexor digitorum

profundus in carpal tunnel24 Fibrous flexor sheath of index

finger25 Abductor pollicis brevis26 Flexor pollicis longus27 Flexor pollicis brevis

28 Abductor digiti minimi29 Flexor digiti minimi brevis30 Opponens digiti minimi31 Triceps

A Muscles of the left upper limb (from the front)B Deep tendons, muscles of the left forearm and hand

(from the front)

Upper limb: anterior muscle groups 139

Location of numbers: 1A; 2A; 3A; 4A; 5A; 6A; 7A; 8A; 9A; 10A; 11A; 12A; 13B; 14A; 15A; 16A; 17AB; 18A; 19A; 20A; 21A; 22A; 23AB; 24B; 25B; 26B;27B; 28B; 29B; 30B; 31A.

Upper limb: posterior musclegroups

Elbow extension

Triceps (1) arises by two heads from the humerus andone from the scapula (infraglenoid tubercle) to insertinto the olecranon of the ulna. With a little help fromanconeus, triceps extends the elbow. It is supplied bybranches of the radial nerve (C6,7,8) that arise high inthe axilla. The triceps reflex tests C7 and C8.

Muscles in the posterior aspect of the forearm arefor: supination; wrist (carpal) extension, plus radial orulnar deviation; finger (digit) extension; and thumb(pollicis) extension and abduction. Most arise fromthe common extensor origin (CEO) on the anterioraspect of humeral lateral epicondyle, and surroundingfascia. Functionally, brachioradialis (6) is an excep-tion. It arises from the lateral supracondylar ridge ofthe humerus and passes to the lower end of the radius,just proximal to the styloid process. It is an elbowflexor, particularly when the forearm is in the mid-prone position. Nerve supply is from the radial (C5,6).

Supination

Supinator is a deeply situated muscle that arises fromthe CEO and the ulna. The posterior interosseous(deep) branch of the radial nerve passes between thesetwo heads and supplies them. Supinator wraps aroundthe posterior aspect of the radius to insert into its lat-eral surface. Its contraction ‘unwinds’ the pronatedradius into supination. Like biceps, the other musclethat supinates, its segmental supply is C5,6.

Wrist extension

Power grip (e.g. holding a racket) is dependent onwrist extension, usually with radial deviation to coun-teract gravity. Therefore there are two extensors onthe radial side and one on the ulnar. Extensor carpiradialis longus (7) arises from the CEO and the adja-cent supracondylar ridge. It inserts into the secondmetacarpal. Extensor carpi radialis brevis (8) arisesfrom the CEO to insert into the third metacarpal (thetwo extensor attachments mirror those of flexor carpiradialis). Extensor carpi ulnaris (9) arises from theCEO and ulna, to insert into the fifth metacarpal. All

the muscles extend the wrist, with radial or ulnar devi-ation as the name implies. The radial nerve, or its pos-terior interosseous branch (C6,7,8) supplies thesemuscles.

Finger extension

Extensor digitorum (10) arises from the CEO andadjacent fascia, along with extensor digiti minimi(11), which runs parallel with it. Extensor indicis (12)arises from the ulna and interosseous membrane. Themuscles form tendons that become the extensorexpansions (13) inserting into all three phalanges ofeach finger to extend the metacarpophalangeal andinterphalangeal joints. The index finger has two ten-dons, extensor digitorum and extensor indicis. Thelittle finger also has two tendons, but these are derivedfrom the divided tendon of extensor digiti minimi(14) with only a small contribution from extensor dig-itorum (15). Fibrous bands (intersections) (16) linkthe extensor tendons, making it difficult to extendindividual fingers, except for the index (pointing) fin-ger. The posterior interosseous nerve (C7,8) suppliesall these muscles.

Thumb abduction and extension

These muscles originate deeply, and all have fibresarising from the interosseous membrane. Abductorpollicis longus (17) also arises from the ulna andradius; extensor pollicis longus (18) from the ulna;and extensor pollicis brevis (19) from the radius. Themuscles become tendinous and pass to the thumb.Abductor longus runs with the extensor brevis butinserts into the base of the first metacarpal, while bre-vis inserts into the base of the proximal phalanx.Extensor longus glides around a tubercle on the poste-rior aspect of the radius, then inserts into the base ofthe distal phalanx of the thumb. The muscles abductand extend the thumb, as implied by their names. Theposterior interosseous nerve (C7,8) supplies them all.

The extensor retinaculum (20) arises from theradius and runs across the back of the wrist to the pisi-form and hamate. All the above tendons run in syn-ovial sheaths beneath the retinaculum. The sheathscommence proximal to the retinaculum but continueinto the hand distally. They may become inflamed dueto excess activity (tenosynovitis).

140 The Upper Limb

A B

2

13

5

6

7

8

19

12

16

20

911

107

17

19

4 18

8

13

1514 14

2018

4

19

1710

9

11

4

Prox

PA

D

Prox

M(UL)

Lat(Rad)

D

1 Triceps2 Deltoid3 Biceps4 Cephalic vein5 Coracobrachialis6 Brachioradialis

7 Extensor carpi radialis longus8 Extensor carpi radialis brevis9 Extensor carpi ulnaris

10 Extensor digitorum11 Extensor digiti minimi12 Tendon of extensor indicis

13 Extensor expansion14 Divided tendon of extensor digiti

minimi15 Contribution of extensor

digitorum to extensor digitiminimi

16 Fibrous intersections betweenextensor tendons

17 Abductor pollicis longus18 Extensor pollicis longus19 Extensor pollicis brevis20 Extensor retinaculum

A Muscles of the left upper limb (from behind)B Superficial dissection of the dorsum of the left hand

(from behind)

Upper limb: posterior muscle groups 141

Location of numbers: 1A; 2A; 3A; 4AB; 5A; 6A; 7AB; 8AB; 9AB; 10AB; 11AB; 12B; 13B; 14B; 15B; 16B; 17AB; 18AB; 19AB; 20AB.

Superficial palm of hand,median nerve

The hand is for reaching out, touching, feeling (evenidentifying), manipulating and gripping. The skin isadherent to the underlying palmar aponeurosis (1),which receives palmaris longus (2) and passes fromthe flexor retinaculum (3) to the fibrous flexorsheaths of the fingers (4). The skin is highly sensitive.The palm may be ‘cupped’ for grip, aided by palmarisbrevis (6) and the digits flex, extend, abduct andadduct. The thumb has the additional function ofopposition.

Skin sensory supply is from the ulnar nerve (7) tothe palmar and dorsal aspects of the medial (ulnar)side of the hand. It gives the dorsal and palmar digitalbranches (8) to both aspects of the medial (ulnar) oneand a half digits, including the nail beds. The tip of thelittle finger is the ulnar nerve autonomous area. Theremainder of the dorsum (except nail beds) is suppliedby the radial nerve, the first dorsal web space being theautonomous area. The median nerve (11) supplies thepalmar aspect of the lateral (radial) palm, and via itsdigital branches (12) the lateral three and half digits,including the nail beds. The tip of the index finger isthe autonomous area.

The thenar and hypothenar eminences are createdby the small muscles for the thumb and the equivalentones (in brackets) for the little finger. These are:abductor pollicis brevis (14) (digiti minimi (15));flexor pollicis brevis (16) (digiti minimi (17)); andmore deeply opponens pollicis (opponens digiti min-imi (18)). Objects may be held in the ‘cup’ of thepalm, between the eminences.

The actions of the muscles (although limited for thelittle finger) are implied by the name. Hypothenarmuscles (ulnar nerve) arise from the flexor retinacu-lum, pisiform and hamate. Thenar muscles (mediannerve) arise from the flexor retinaculum, scaphoid andtrapezium. Whatever the nerve supply, the root valueis T1 (like all other small muscles in the hand). Thumbopposition is a uniquely human movement anddependent on the saddle-shaped first carpometacarpal

joint. Opponens pollicis attaches to the length of thefirst metacarpal and swivels it to help carry the thumbinto opposition. Flexor and abductor pollicis brevisattach to the proximal phalanx.

Median nerve

The median nerve (C5,6,7,8,T1) in the arm lies lateralto the brachial artery, but then crosses it to lie medialto the artery in the antecubital fossa. It then passesbetween the two heads of pronator teres to lie deep toflexor digitorum superficialis (19) in the forearmbefore passing through the carpal tunnel and into thehand.

The median nerve may be injured at the elbow. Thethumb flexors are lost, as well as flexor digitorumsuperficialis to all fingers, and flexor profundus to theindex and middle fingers. When asked to make a fist thepatient can only flex the ring and little fingers, ‘the handof benediction’. Sensory loss may be variable due to nerveoverlap, but there is always loss to the skin of the pulpover the distal phalanx of the index finger, i.e. theautonomous area of the median nerve. An extensivesensory loss to the hand following median nerve injury isparticularly debilitating as patients injure (e.g. burn) them-selves without realizing it, and manual dexterity isdependent on accurate sensation.

The long flexor tendons, in their common synovialsheath, pass into the palm behind the flexor retinacu-lum, a band of fibrous tissue from the pisiform andhook of hamate, across to the trapezium and scaphoid.Its proximal edge lies at the distal skin crease of thewrist. The ulnar nerve, and accompanying artery passin a small canal of their own, anterior to the flexor reti-naculum.

The median nerve runs with the tendons in the carpaltunnel (behind the retinaculum) where it may be com-pressed causing carpal tunnel syndrome. Signs and symp-toms may include weakness and wasting of the thenarmuscles with sensory disturbance over the radial threeand half digits but not over the palm and thenar emi-nence. The latter skin areas are supplied by a superficialbranch of the median nerve that arises proximal to, andpasses into the palm, superficial to the flexor retinaculum.

142 The Upper Limb

A B

1015

314

16

12

121212

18

6

17

8

88

9115

7

10

19

13

19

135

7 11

9

2

3

146

17 116

4

Prox

Lat(Rad)

M(UL)

D

Prox

Lat(Rad)

M(UL)

D

1 Palmar aponeurosis2 Palmaris longus3 Flexor retinaculum4 Fibrous sheath of middle finger5 Ulnar artery

6 Palmaris brevis7 Ulnar nerve8 Digital branches of ulnar nerve9 Radial artery

10 Flexor carpi radialis

11 Median nerve12 Digital branches of median

nerve13 Flexor carpi ulnaris14 Abductor pollicis brevis

15 Abductor digiti minimi16 Flexor pollicis brevis17 Flexor digiti minimi brevis18 Opponens digiti minimi19 Flexor digitorum superficialis

A Superficial structures of the left forearm and palm (fromthe front)

B Palm of the left hand, arteries and nerves (from thefront)

Superficial palm of hand, median nerve 143

Location of numbers: 1A; 2A; 3AB; 4A; 5AB; 6AB; 7AB; 8B; 9AB; 10AB; 11AB; 12B; 13AB; 14AB; 15B; 16AB; 17AB; 18B; 19AB.

Deep palm, ulnar nerve, arteries

Muscles of the deep palm

Four lumbrical muscles (1) arise in the palm from thetendons of flexor digitorum profundus (2) and passdistally and posteriorly to attach to the radial aspect ofthe extensor tendon (expansion) of each finger. Themedial (ulnar) two are bicipital and supplied by theulnar nerve (5). The lateral (radial) two are unicipitaland supplied by the median nerve (6).

Two sets of interosseous muscles arise between themetacarpal bones. Whatever the name or origin, likethe lumbricals, they lie in the palm and pass anteriorto the metacarpophalangeal joints. They attach to theproximal phalanges and the extensor expansions ofthe fingers. Palmar interossei adduct (palmar: PAD)the fingers toward the middle finger whereas dorsalinterossei abduct (dorsal: DAB) the fingers away fromthat axis. The middle finger cannot adduct to itself,therefore does not have palmar interossei. As a result,there are three palmar interossei (8) passing one eachto the side (closer to the middle finger) of the index,ring and little fingers. The middle finger can beabducted from its own axis therefore it has two dorsalinterossei. So there are four dorsal interossei (9), onepassing to each side of the middle finger, and one eachto the side (away from the middle finger) of the indexand ring fingers. The thumb and little finger do notneed dorsal interossei as they have their own abduc-tors (10,11). Similarly, the thumb does not need a pal-mar interosseous as it has its own adductor pollicis(12) passing from the carpal bones and thirdmetacarpal to the base of the proximal phalanx. Whenthe lumbricals and interossei function together, whichis usual, they flex the metacarpophalangeal joints,because they pass anterior to them, and they extendthe interphalangeal joints because they insert into theextensor expansions.

The deep branch of the ulnar nerve (13) supplies allthe interossei and adductor pollicis. All small musclesof the hand are supplied by T1, via the ulnar nerve,except the lateral two lumbricals and the muscles ofthe thenar eminence (T1 via the median nerve).

Ulnar nerve

The ulnar nerve (C8,T1) lies medially in the arm, ontriceps. It passes behind the medial humeral epi-condyle and between the two heads of flexor carpiulnaris before passing distally, medial to the ulnarartery (14), into the hand. The ulnar nerve may beinjured as it passes posterior to the medial epicondyle,or at the wrist where it is superficial to the flexor reti-naculum in the canal of Guyon. Injury to the ulnarcauses loss of all interossei and the two medial lumbricals,as well as adductor pollicis. Therefore, the two medial fin-gers form an ‘ulnar claw’: extended at the metacarpopha-langeal joints and flexed at the interphalangeal joints as aresult of loss of interphalangeal extension and metacar-pophalangeal flexion (the combined actions of the lumbri-cals and interossei). This is less marked if the injury is atthe elbow as flexor digitorum profundus is also lost. Thefingers cannot be abducted from the axis of the middlefinger (dorsal interossei) or adducted toward it (palmarinterossei). Thumb adduction is lost and if patients areasked to hold a sheet of paper by adducting the thumbto the palm, they will use the thumb flexors, which aresupplied by the median nerve (Froment’s sign).

Palmar arteries

The ulnar and radial arteries (15) pass into the palm.The ulnar runs anteriorly, but the radial courses poste-riorly before it passes between the first twometacarpals to enter the palm in a deep position.Branches of the arteries anastomose to form superficialand deep palmar arches (16). The latter lies deep tothe long tendons, whereas the former is anterior. Thesuperficial arch lies opposite the cleft of the out-stretched thumb, the deep arch about one finger-breadth proximally.

The arches give metacarpal arteries (17) that divideto give both dorsal and palmar digital arteries (18) toeach side of the digit. Digital nerves (19,20) accom-pany these. Injury to the anastomotic palmar arches maycause profuse bleeding. The digital nerves may be anaes-thetized (ring block) to carry out minor operations on thedigits.

144 The Upper Limb

A

B

C

4

4

15

143

510

4

102

11

3

1 11

1216

98

17

98

18 18

63

5 7

13

20 20 19 19 19

Prox

Lat(Rad)

M(UL)

D

Prox

Lat(Rad)

M(UL)

D

Prox

Lat(Rad)

M(UL)

D

1 Lumbrical muscles2 Tendons of flexor digitorum

profundus in carpal tunnel3 Flexor carpi ulnaris4 Flexor carpi radialis5 Ulnar nerve

6 Median nerve7 Flexor retinaculum8 Palmar interossei9 Dorsal interossei

10 Abductor pollicis brevis11 Abductor digiti minimi

12 Adductor pollicis13 Deep branch of ulnar nerve14 Ulnar artery15 Radial artery16 Deep palmar arch17 Metacarpal artery

18 Palmar digital artery19 Digital branches of median

nerve20 Digital branches of ulnar nerve

A Deep dissection of left palm, nerve supply (from the front)B Deep dissection of left palm, arterial supply (from the front)C Deep dissection of left palm, muscles and tendons (from the front)

Deep palm, ulnar nerve, arteries 145

Location of numbers: 1C; 2C; 3ABC; 4ABC; 5AB; 6A; 7A; 8B; 9B; 10BC; 11C; 12B; 13A; 14B; 15B; 16B; 17B; 18B; 19A; 20A.

Axillary artery, brachial plexus,radial nerve

Axillary artery

The axillary artery with vein (1,2) medially, is the con-tinuation of the subclavian as it passes over the firstrib. It becomes the brachial artery (3) at the inferioredge of teres major (4). The axillary artery suppliesbranches to the muscles on the chest wall, the arm,and those that bound the axilla (5–11). Its branchesprovide important contributions to anastomosesaround the scapula and the elbow. In the female itslateral thoracic branch (12) is an important bloodsupply to the breast.

Brachial plexus

The plexus is formed by the ventral rami of spinalnerves C5–8 and T1. These are the roots of thebrachial plexus that supplies the upper limb. C5–8emerge into the neck between scalenus anterior andmedius. T1 emerges inferior to the neck of the first rib,but joins the plexus above the apex of the lung.

C5 and C6 form the upper trunk, C7 continues asthe middle trunk, while C8 and T1 form the lowertrunk. The trunks pass laterally and lie around the sub-clavian artery while passing over the first rib to enterthe axilla, between the clavicle and the scapula.Behind the clavicle, each trunk splits into anterior andposterior divisions. These recombine to form the pos-terior (13), lateral (14) and medial (15) cords aroundthe axillary artery. The upper roots (C5–7) tend tostay lateral, the lower roots (C8,T1) tend to staymedial. All roots contribute to the posterior cord, andtherefore also to the radial nerve. The median nerve isformed from both lateral and medial cords, thereforealso contains all roots. Proximal muscles tend to besupplied by nerve roots that emerge from higher seg-ments of the spinal cord. Distal muscles are suppliedby nerves arising from the lower segments. The fivemain branches of the brachial plexus are median (16),ulnar (17), radial (18), axillary (19) and musculocu-taneous (20) nerves.

Branches from both lateral and medial cords supplythe pectoral muscles. After supplying the pectorals

and contributing to the median nerve, the lateral cordbecomes the musculocutaneous nerve. Subscapularis,teres major and latissimus dorsi are supplied by theposterior cord, which also gives the axillary nerve todeltoid and teres minor before continuing as the radialnerve. The medial cord contributes to the mediannerve, and also gives cutaneous nerves to the medialarm and forearm before continuing as the ulnar nerve.

Upper trunk injury removes C5 and C6, which supplythe shoulder abductors and external rotators, and theelbow flexors and supinators. Consequently, the upperlimb lies at the side adducted and internally rotated. Theelbow is extended and pronated. The fingers may flexslightly and the condition, Erb’s palsy, is often called‘waiter’s tip’ palsy. Lower trunk injury (Klumpke’s paraly-sis) removes C8 and T1, therefore all the thenar andhypothenar muscles are affected, along with the lumbri-cals and interossei. The hand is flattened and the fingersclawed.

Radial nerve

The radial nerve (C5–8,T1) as well as sending cuta-neous branches to the posterior aspects of arm andforearm, supplies triceps, and its posteriorinterosseous branch supplies the wrist, finger andthumb extensors. The radial nerve may be injured as itwinds posteriorly around the midshaft of the humerus. Ifso, triceps will be spared as the nerve supply arises in theaxilla, but wrist and finger extension will be lost. The maindisability is the loss of power grip, as that depends onwrist extension. There will be sensory loss over the firstdorsal web space, the autonomous area of the radialnerve.

In the antecubital region the radial nerve lies deep tobrachioradialis. After giving the posterior interosseousbranch it continues into the forearm lying lateral tothe radial artery, to supply the skin of the dorsum ofthe hand and radial three and a half digits (but not thenail beds). The posterior interosseous passes betweenthe two heads of supinator (therefore supplies it) andcontinues to supply all the muscles in the extensoraspect of the forearm. It lies close to the radius and maybe injured in fractures of that bone or during surgical plat-ing of the fracture.

146 The Upper Limb

1 Axillary artery2 Axillary vein3 Brachial artery4 Teres major5 Pectoralis minor6 Pectoralis major

7 Deltoid8 Short head of biceps9 Subscapularis

10 Latissimus dorsi11 Serratus anterior12 Lateral thoracic artery

13 Posterior cord14 Lateral cord15 Medial cord16 Median nerve17 Ulnar nerve18 Radial nerve

19 Axillary nerve20 Musculocutaneous nerve21 Long thoracic nerve22 Thoracodorsal nerve

A Left axilla and brachial plexus (from the left and front)B Left axilla and brachial plexus with displacement of

nerves (from the left and front)

Axillary artery, brachial plexus, radial nerve 147

A

B

7

75

6

6

5

114

219 22

10

31615

12

2 113

141918

20

17

6

8

5

6

8

316

17

1022

9

21

411

6

6

5

12 12

15

14

20

S

Lat(L)

M

I

S

Lat(L)

M

I

Location of numbers: 1AB; 2AB; 3AB; 4AB; 5AB; 6AB; 7AB; 8AB; 9AB; 10AB; 11AB; 12AB; 13B; 14AB; 15AB; 16AB; 17AB; 18B; 19B; 20AB; 21AB; 22AB.


The LowerLimb

Part IX

64 Lower limb: fascia, superficial veins, sural nerve, lymph nodes 150

65 Hip joint, prevention of pelvic tilt 15266 Knee joint 15467 Tibiofibular, ankle and tarsal joints,

arches of foot 15668 Sole of foot: plantar aponeurosis,

muscle layers, neurovascular supply 15869 Lower limb: anterior muscle groups 16070 Lower limb: posterior muscle groups 16271 Buttock musculature, sciatic nerve 164

Lower limb: fascia, superficialveins, sural nerve, lymph nodes

Deep fascia

The deep fascia (1) is like a stocking encompassing thewhole lower limb. In the thigh it is named fascia lata,which attaches to the inguinal ligament (2) and also tothe bony prominences: iliac crest, ischium, pubic arch,femoral condyles. The fascia lata is continuous withthe deep fascia of the leg, attaching to the tibialcondyles, head of fibula and subcutaneous border ofthe tibia (3). At the ankle it is specialized to formflexor, extensor and fibular (peroneal) retinacula (4),before continuing with the fascia of the foot. In thethigh fascia lata is thinner medially and has an opening(cribriform fascia) to transmit the great saphenousvein (5). Laterally it is thickened to form the iliotibialtract (8), which runs from the ilium to the upper ante-rior part of the lateral tibial condyle. It receives twomuscles and is an important stabilizer of both hip andknee joints, therefore of the lower limb.

Intermuscular septa pass from the deep fascia to liebetween muscles and provide muscle origin as well asdefinite compartments. In the thigh septa separate thequadriceps and adductor muscles from the hamstrings.Sartorius (10) has a layer of fascia separating it fromthe underlying muscles and forming the subsartorialcanal, which transmits the femoral vessels on theirway to pierce adductor magnus and continue aspopliteal vessels. In the leg, particularly the calf, thefascial compartmentalization ensures that as musclescontract the deep veins are compressed, aiding venousreturn to the heart (the muscle pump). But muscledamage or bone fracture may cause swelling thatbecomes restricted within the compartment. In turn theraised pressure will constrict and obstruct neurovascularsupply. Such compartment syndrome often must bereleased surgically by cutting the fascia before muscleischaemia and necrosis occur.

Superficial veins of the lower limb

The veins are divided into superficial and deep groups.The superficial veins are variable but do consistently

show the great (long) and small (short) saphenousveins. All veins have valves and flow is from superfi-cial, via perforators to the deep system, which paral-lels the arteries, and then proximally. The superficialveins also freely communicate with each other.

The great saphenous vein starts on the dorsum of thefoot. It passes 2 cm anterior to the medial malleolus(11) where it is constant. It may be approached, by cut-ting down through the skin, for emergency venousaccess. The saphenous nerve, lying alongside, may besevered causing sensory deficit on the medial border ofthe foot. The vein ascends up the medial leg to lieimmediately posterior to the medial femoral condyle(one hand-breadth behind the patella). It then passesup the medial thigh and through the cribriform fascia,2.5 cm below and lateral to the pubic tubercle, toenter the femoral vein (12). It receives a number oftributaries just before passing through the fascia. Thesemust be identified during varicose vein surgery.

The great saphenous has perforators, with valves,around the ankle and knee. Should the valves becomeincompetent blood may flow from deep to superficial andthe superficial veins become tortuous and dilated (vari-cose veins). This slows venous return, leading ultimately toskin changes around the ankle (lipodermatosclerosis),which may ulcerate following injury. Varicose veins maybleed profusely if injured.

The small saphenous vein (13) passes behind thelateral malleolus (14) and ascends up the posterioraspect of the calf to enter the popliteal vein (15)behind the knee. The sural nerve (16) is derived fromboth the tibial (17) and common fibular (18) nerves.It lies with the small saphenous vein and supplies theskin of the posterior calf and lateral border of the foot.The sural may be harvested for nerve grafting.

Lymph nodes

These are found in the popliteal fossa and inguinalregion. The superficial inguinal are in two groups thatform a ‘T’ at the upper end of the great saphenousvein, and parallel with, but just inferior to the inguinalligament. They drain to the deep inguinal nodes justmedial to the femoral vein, and through the femoralcanal to the iliac nodes.

150 The Lower Limb

A

D

B

C

S (Dor)

P (Prox)A (D)

I (Plan)

20 8

21

19

10

5

9

19

20

17

15

18

2425

16

13

5

26

1411

8

21

10

22

3

5

25

23

1114

72

612

1

4

28

27

4

16

14

13

Prox

LatM

D

Prox

Lat(Fib)

M(Tib)

D

Prox

M(Tib)

Lat(Fib)

D

1 Deep fascia of the leg2 External oblique aponeurosis

becoming the inguinal ligament3 Shaft of tibia4 Retinacula5 Great saphenous vein6 Femoral artery7 Femoral nerve8 Cut edge of iliotibial tract

9 Tensor fasciae latae10 Sartorius11 Medial malleolus12 Femoral vein13 Small saphenous vein14 Lateral malleolus15 Popliteal vein16 Sural nerve17 Tibial nerve

18 Common fibular (peroneal)nerve

19 Rectus femoris20 Vastus lateralis21 Vastus medialis22 Tibialis anterior23 Soleus24 Lateral head of gastrocnemius25 Medial head of gastrocnemius

26 Calcaneal tendon (Achillestendon)

27 Medial branch of superficialfibular (peroneal) nerve

28 Lateral branch of superficialfibular (peroneal) nerve

A Left thigh (from the front)B Left lower limb superficial structures

(from the front)C Left lower limb superficial structures

(from behind)D Left foot (from the front and left)

Fascia, superficial veins, sural nerve, lymph nodes 151

Location of numbers: 1D; 2A; 3B; 4D; 5ABC; 6A; 7A; 8AB; 9A; 10AB; 11BC; 12A; 13C; 14BCD; 15C; 16CD; 17C; 18C; 19AB; 20AB; 21AB; 22B; 23B; 24C;25BC; 26C; 27D; 28D.

Hip joint, prevention of pelvic tilt

Hip joint

As the pelvic girdle is barely flexible, movement of thelower limb is largely at the hip joint, which also trans-mits the body weight. When compared with theshoulder, the synovial ball and socket hip hasincreased stability but reduced mobility. The head ofthe femur (1) lies within the deep socket of theacetabulum (2); itself deepened by the fibrocartilagelabrum (3). The femoral head is offset from thefemoral shaft (4) by the femoral neck (5), whichmeans all hip movements become rotation of the headwithin the acetabulum.

The fibrous capsule (6) arises from the acetabularmargins and the labrum. It passes laterally to enclosethe head and much of the neck of the femur.Anteriorly it attaches to the intertrochanteric line butposteriorly falls short of the intertrochanteric crest toleave space for the insertion of the lateral rotator mus-cles onto the femoral neck and the medial aspect ofthe greater trochanter (7). As the capsule attaches tothe femoral neck fibres pass medially up the necktoward the head. These retinacular fibres carry theblood supply to the femoral head.

Ligaments arising from the three elements of the hipbone strengthen the capsule. The ilio-, pubo- andischiofemoral ligaments arise adjacent to the acetabu-lum and pass, as part of the capsule, to insert into thefemoral neck and intertrochanteric line. As humanshave adapted to stand erect the hip joint is alreadyextended, and any further extension is limited. Theligaments tend to spiral around the joint and are par-ticularly supportive in this upright position. The liga-ment of the head of the femur (8) passes from theacetabulum to the femoral head and may carry someblood supply, particularly in the young.

Hip movements

Hip flexion. Iliopsoas (9,10,11) arises from the lum-bar vertebrae and intervening discs, and from the inneraspect of the ilium, to attach to the lesser trochanter.Psoas is supplied segmentally mainly by L1 and L2,and iliacus by L2 and L3 via the femoral nerve.

Hip adduction. Pectineus (12), adductor longus (13)and brevis (14), and magnus arise from the pubis andischium, and attach to the femur. Gracilis (15), alsofrom the pubis, passes to the tibia and has additionalfunctions of knee flexion and internal rotation of thetibia. The small, tendinous origin of adductor longus isthe site of ‘groin strain’.

The obturator nerve (L2–4 anterior divisions) emergesfrom the medial side of psoas major in the pelvis. Itpasses on the lateral pelvic wall, then through theobturator foramen and into the medial thigh. It splitsinto two branches, one on either side of adductorbrevis and supplies all the adductors (exceptpectineus, which is femoral) and the skin of the medialthigh. If it is injured some adduction remains via thesciatic supply to magnus. Branches of the femoral andobturator nerves supply both the hip and knee thereforethe two joints may refer pain to each other.

Prevention of pelvic tilt

During walking, or standing on one leg gravity makesthe body topple to the unsupported side. The adduc-tors act synergistically with the hip abductors (18,19)and the iliotibial tract to support the weight of thebody and hold the pelvis level. The neck of the femurgives mechanical advantage to the abductors.Shortening of the neck (congenital dislocation of the hip,prosthetic hip) will weaken the supportive effect of theabductors and the pelvis will dip to the opposite sidewhen walking (Trendelenburg gait).

Fractures of the neck of the femur, within the capsule,usually tear the retinacular fibres, cutting off the bloodsupply to the femoral head and causing avascular necro-sis. Iliopsoas pulls the lower limb upward and externallyrotates it, as the axis of movement following the fractureis through the femoral shaft. The limb appears shortenedand the foot laterally rotated. Severe trauma may cause aposterior dislocation of the hip that may fracture asmall piece of bone from the acetabulum. That bony frag-ment may damage the sciatic nerve, which lies immedi-ately behind the joint. A central dislocation occurs whensevere trauma pushes the femoral head through theacetabulum.

152 The Lower Limb

1 Head of femur2 Rim of acetabulum3 Acetabular labrum4 Shaft of femur5 Neck of femur6 Capsule of hip joint7 Greater trochanter

8 Ligament of the head of femur(ligamentum teres)

9 Psoas major10 Iliopsoas tendon11 Iliacus12 Pectineus13 Adductor longus

14 Adductor brevis15 Gracilis16 Femoral vein17 Femoral artery18 Gluteus minimus19 Gluteus medius20 Ilium

21 Articular cartilage22 Tensor fasciae latae23 Obturator externus24 Vastus medialis25 Vastus lateralis26 Sartorius27 Rectus femoris

A Coronal section through the left hip joint (from the front)B Left thigh (from the front)

Line diagram adapted from Ellis H, Logan BM, Dixon AK (2001)Human Sectional Anatomy. London: Arnold.

Hip joint, prevention of pelvic tilt 153

A

B9

20

18 19

1122

26

1716

1214

15

1327

25

3

6

21

1

8

2

5

7

23

36

10

13

244

25

Prox

LatM

D

S

LatM

I

Location of numbers: 1A; 2A; 3A; 4A; 5A; 6A; 7A; 8A; 9A; 10A; 11B; 12B; 13AB; 14B; 15B; 16B; 17B; 18A; 19A; 20A; 21A; 22B; 23A; 24A; 25AB; 26B; 27B.

Knee joint

The knee is a synovial, modified hinge joint betweenthe femur (1) and the tibia (2). Movements are essen-tially flexion and extension, but rotation is possiblewhen the knee is flexed. The patella (3) is a sesamoidbone in the tendon of quadriceps (4,5), and it articu-lates with the femur. The lateral articular surface ofthe patella is larger than the medial. The femoralcondyles (6) are rounded. Anteriorly the lateralcondyle is more prominent than the medial to coun-teract the natural tendency for quadriceps to draw thepatella in a lateral direction during knee extension.The upper end of the tibia (7) is a flat plateau with anintercondylar eminence.

The fibrous capsule attaches to the articular marginsof the femur and tibia. It is created from ligaments,from extensions of the tendons around the joint, andby the patella. Extensions of the quadriceps, the patel-lar retinacula, pass between the patella and the tibia.Laterally, fibres from the iliotibial tract similarlystrengthen the capsule. Posteromedially, it is strength-ened by the oblique popliteal ligament and semimem-branosus (8), and posterolaterally, the capsule isstrengthened by the arcuate popliteal ligament thatarises from the head of the fibula. These tendinousextensions ensure tension of the capsule. Many of thetendons around the joint have bursae between them,the capsule and its ligaments, or other tendons. Thereare subcutaneous bursae (9) over the patella and overthe ligamentum patella, as well as a deep bursabetween the tibia and the ligamentum patella. All thebursae may become inflamed, swollen and tender. Thejoint extends upward behind quadriceps as the supra-patellar bursa (11).

Ligaments

The knee, like all hinge joints, is supported by collat-eral ligaments. The medial collateral is a band that ispart of the capsule and runs from the medial femoralepicondyle to the tibia. The lateral collateral is cord-like and separate from the capsule. It passes from thelateral femoral epicondyle to the fibula (splitting thetendon of biceps femoris).

The cruciate ligaments are within the knee joint, butinvaginated into the synovium from behind, thereforeoutside the synovial sheath. The anterior cruciate (12)arises from the anterior aspect of the tibial intercondy-lar area and passes to the internal aspect of the lateralfemoral condyle. The posterior cruciate (13) arisesfrom the posterior tibial intercondylar area and passesto the inner aspect of the medial femoral condyle. Thetwo ligaments cross each other and are taut in exten-sion. The anterior prevents excessive forward move-ment of the tibia; the posterior prevents excessiveposterior movement. Lateral blows (car bumper) to theextended knee tend to damage the anterior cruciate liga-ment, the medial collateral ligament and with it the medialmeniscus. Injuries to the posterior cruciate ligament leavea patient with difficulty walking downstairs as the femurmay slide forward on the tibia.

The fibrocartilage menisci are between the femurand tibia, making the joint surfaces more congruentand acting as shock absorbers. They are crescentic-shaped wedges that attach to the tibial intercondylararea by their ‘horns’ but peripherally attach to thejoint capsule. They move during flexion and extensionof the knee, but the medial meniscus (14,15) isrestricted as it is, via its capsular attachment, alsoattached to the medial collateral ligament, which ispart of the capsule. The menisci, particularly the medial,may be injured when the femur is traumatically forced torotate on the femur with the knee extended.

As the knee moves normally into full extension, thefemur rotates medially around the axis of the cruciate(particularly anterior) ligaments. The knee is then‘close-packed’ so that the lower limb becomes a sup-portive strut with only minimal continued use ofquadriceps and of the iliotibial tract.

Popliteus (23) must laterally rotate the femur at thestart of knee flexion. It arises from the posterior aspectof the tibia. Its tendon passes through the joint cap-sule, sends a slip to the lateral meniscus (that movesit), before inserting onto the lateral femoral condyle,below the epicondyle. Nerve supply is via the tibialnerve (24) (L4,5,S1).

154 The Lower Limb

1 Shaft of femur2 Shaft of tibia3 Patella4 Patellar ligament (ligamentum

patellae)5 Tendon of quadriceps femoris6 Articular cartilage on medial

femoral condyle

7 Proximal end of tibia (tibialplateau)

8 Semimembranosus9 Prepatellar bursa

10 Infrapatellar pad of fat extendinginto infrapatellar fold

11 Suprapatellar bursa12 Anterior cruciate ligament13 Posterior cruciate ligament

14 Anterior horn of medialmeniscus

15 Posterior horn of medialmeniscus

16 Tibial tuberosity17 Gastrocnemius18 Popliteal vein19 Popliteal artery20 Semitendinosus

21 Sciatic nerve22 Soleus23 Popliteus24 Tibial nerve25 Tendon of plantaris26 Vastus intermedius27 Rectus femoris

A Sagittal section through the left knee from the left

Knee joint 155

A

2726

121

8

20

18

19

18

115

3

6

910

4

2224

25

23

2

16

147

12

15

13

18

17

Prox

PA

D

Line diagram adapted from Ellis H, LoganBM, Dixon AK (2001) Human SectionalAnatomy. London: Arnold.

Tibiofibular, ankle and tarsaljoints, arches of foot

Tibiofibular joints

The tibia (1) and fibula (2) are held together by theinterosseous membrane. Superiorly there is a synovialjoint between the tibia and the head of the fibula.Inferiorly there is a fibrous joint, supported by furtherligaments situated anteriorly and posteriorly.

Ankle joint

At their lower ends, the tibia and fibula clasp the talus(3) to form the ankle joint (4). The tibia is the medial-malleolus (5), while the arrow-shaped inferior end ofthe fibula is the lateral malleolus (6). The talus (andtherefore the foot) moves only in dorsiflexion (exten-sion) and plantarflexion (flexion) between the malle-oli. The ankle joint capsule attaches to the articularmargins. As expected in a hinge joint, it is lax anteri-orly and posteriorly, but strengthened at the sides bycollateral ligaments.

The strong medial collateral (deltoid) ligament (7)is like a triangle with its apex at the medial malleolusand the base formed by its attachment to the navicu-lar (8), spring ligament, sustentaculum tali (calcaneus)and talus. The lateral ligament is in three separatebands. Splaying from the lateral malleolus are: ante-rior talofibular (9) to the neck of the talus; calcane-ofibular to the calcaneus (a band separate from thecapsule); the posterior talofibular passing backward tothe lateral tubercle on the posterior aspect of the talus.

Injury to the ankle ligaments, particularly on the lateralaspect is common. The bruising, swelling and tendernessmay vary depending on which band has been injured.Fractures around the ankle may affect the joint surface,possibly causing the early onset of arthritis, with conse-quent painful limitation to walking and running. Severeinjury may also disrupt the inferior tibiofibular joint. Thetrochlear surface of the talus is wider anteriorly and if theankle is immobilized in plaster the foot must be dorsi-flexed so that the broader part of the talus is in the‘socket’ between the tibia and fibula. The posterior tibial

neurovascular bundle lies behind and below the medialmalleolus and may be at risk in fractures and dislocationof the ankle.

Tarsal joints

The foot has a series of joints between all the tarsalbones. These may be simplified and collectivelyreferred to as the subtarsal joint, which includes: talusto calcaneus and navicular; calcaneus to cuboid(10,11) (sometimes called midtarsal). These joints aresynovial, have fibrous capsules and are supported byligaments. They allow for inversion and eversion of thefoot.

Arches of the foot

The arches are formed naturally as the bones of thefoot articulate with each other. Each foot has a longi-tudinal arch, described as having medial and lateralcomponents. The medial arch of calcaneus (12), talus,navicular, cuneiforms (13) and the three medialmetatarsals (14) is highly arched before reaching theground again at the metatarsal heads and phalanges(15,16). The head of the talus (19) is the highestpoint, or keystone of the arch. The lateral arch of cal-caneus and cuboid to the lateral two metatarsals andphalanges is much lower. Each foot forms half of atransverse arch, which is complete when the feet areplaced together.

As well as the ligaments and small muscles, the longtendons within the sole also support the arches.Tibialis anterior and posterior hold up the medial arch,which is also supported by the tendon of flexor hallu-cis longus (20) and the plantar aponeurosis (21).Fibularis (peroneus) longus and brevis support the lat-eral longitudinal arch, but the tendon of longus passesin a groove beneath the cuboid to insert into themedial cuneiform and first metatarsal, therefore alsomaintaining the transverse arch.

The arches act as shock absorbers but are also impor-tant in the propulsive phases of walking and running,where traction on the plantar aponeurosis makes thembecome higher.

156 The Lower Limb

1 Tibia2 Fibula3 Talus4 Ankle joint5 Medial malleolus6 Lateral malleolus7 Medial collateral (deltoid) ligament8 Navicular9 Anterior talofibular (lateral

collateral) ligament of ankle

10 Cuboid11 Calcaneocuboid joint12 Calcaneus13 Medial cuneiform14 First metatarsal bone15 Proximal phalanx of hallux16 Distal phalanx of hallux17 Sesamoid bone18 Tendon of tibialis posterior19 Head of talus

20 Tendon of flexor hallucislongus

21 Plantar aponeurosis22 Abductor hallucis23 Flexor digitorum brevis24 Abductor digiti minimi25 Talocalcaneal interosseous

ligament26 Tendon of flexor digitorum

longus

27 Tendon of fibularis (peroneus)brevis

28 Flexor digitorum longus29 Soleus30 Gastrocnemius31 Calcaneal (Achilles) tendon32 Flexor hallucis longus

A Coronal section through the left ankle joint and foot(from the front) with the foot in plantarflexion

B Sagittal section through the left foot (from the right)

Line diagrams adapted from Ellis H, Logan BM, Dixon AK (2001)Human Sectional Anatomy. London: Arnold.

Tibiofibular, ankle and tarsal joints, arches of foot 157

A

B

1

2

5 6

4

3

25

9

1211

27

24

3029 28

1

31

1615

1413

819

3

12

21

20

4

32

17

23

2622

18

7

2010

Prox

AP

D

Prox

LatM

D

Location of numbers: 1AB; 2A; 3AB; 4AB; 5A; 6A; 7A; 8B; 9A; 10A; 11A; 12AB; 13B; 14B; 15B; 16B; 17B; 18A; 19B; 20AB; 21B; 22A; 23A; 24A; 25A;26A; 27A; 28B; 29B; 30B; 31B; 32B.

Sole of foot: plantar aponeurosis,muscle layers, neurovascularsupply

Plantar aponeurosis

Although the functions of the palm and sole are differ-ent, the topography is similar. The thick plantar skinattaches to the underlying plantar aponeurosis (1),which passes forward from the tuberosity on the pos-terior aspect of the inferior surface of the calcaneus toattach to the fibrous flexor sheaths of each toe. Theaponeurosis sends septa into the foot. These createcompartments and give origin to some of the smallmuscles of the sole. The most important function ofthe plantar aponeurosis is maintenance of the longitu-dinal arch. In walking, the toes are forced into dorsi-flexion, pulling on the aponeurosis, and in turn pullingon the calcaneus to heighten the arch.

Muscle layers

The muscles in the sole move the toes and support thearches. They are arranged in layers, like the palm. Thesuperficial layer is formed by abductors hallucis (2)and digiti minimi (3), which have minimal actionssuggested by their names, and lie on either side offlexor digitorum brevis (4) (equivalent to flexor digi-torum superficialis (forearm)). It arises from the calca-neus and passes forward as the four tendons for thelateral toes. These tendons run into fibrous sheaths,split to allow the passage of flexor digitorum longusand insert into the sides of the middle phalanges.

The second layer contains flexor digitorum longus(7) that gives origin to the lumbricals (8), and receivesflexor accessorius (9), which arises from the calcaneusand inserts into the tendons of longus to straightentheir oblique pull. The tendon of flexor hallucislongus (10) passes into the sole, immediately inferiorto the sustentaculum tali and the spring (plantar calca-neonavicular) ligament. It lies superior to the tendonsof flexor digitorum longus before running forward toenter the fibrous flexor sheath of the hallux and insertinto the base of the distal phalanx. It flexes the halluxand gives powerful propulsion in walking.

The third layer contains flexor hallucis brevis (12)

and flexor digiti minimi brevis (13), which lie oneither side of adductor hallucis. Both arise from thetarsal bones and ligaments, insert into the proximalphalanges and carry out the actions indicated by theirnames. Flexor hallucis brevis attaches to both sides ofthe phalanx and the tendons may contain sesamoids.

The fourth, and deepest, layer contains the plantarand dorsal interossei, which adduct and abduct aroundthe axis of the second toe.

Neurovascular supply

The posterior tibial neurovascular bundle passes intothe sole above flexor digitorum brevis. The tibial nerve(14) divides into medial (15) and lateral (16) plantarnerves, equivalent to the median and ulnar nerves.

The medial plantar nerve supplies the small musclesfor the big toe (except the adductor) and flexor digito-rum brevis (median nerve supplies superficialis in theforearm and the thenar muscles). It also supplies onlythe first lumbrical, as the axis for the foot is the secondtoe rather than the middle one. The lateral plantarsupplies all the other muscles, including flexor acces-sorius (which does not have an equivalent in thehand), adductor hallucis, all the interossei and the lat-eral three lumbricals. Although rare, injury to the lateralplantar nerve may cause clawing of the foot.

Much of the skin on the medial sole and medialthree and half toes (including nail beds), is supplied bythe medial plantar nerve, and on the lateral aspect andlateral one and half toes (and nail beds) by the lateralplantar. Skin on the medial border of the foot is sup-plied by the saphenous nerve, whereas the sural nervesupplies the lateral border and heel. Whatever thenerve supply, the muscles of the sole are supplied byS1,2,3 and the dermatomes are L4,5 and S1 frommedial to lateral.

The posterior tibial artery (17) divides into medial(smaller) and lateral plantar (larger) branches. Theypass above flexor digitorum brevis to supply the footand toes. The lateral plantar forms a plantar arcadewith a branch coming between the metatarsals fromthe dorsalis pedis. Metatarsal branches from thearcade send plantar digital arteries to the toes. Anarcade on the dorsum, from the anterior tibial artery,sends dorsal metatarsal and dorsal digital arteries.

158 The Lower Limb

A

B

C

18

1

2

56

714

11

17

9

15

10

8

19

21

4 16

3

1310

12

15

1

A (D)

LatM

P (Prox)

S (Dur)

A (D)P(Prox)

I(Plan)

A (D)

LatM

P (Prox)

1 Plantar aponeurosis2 Abductor hallucis3 Abductor digiti minimi4 Flexor digitorum brevis5 Medial malleolus of tibia

6 Tibialis posterior7 Flexor digitorum longus8 Lumbrical9 Quadratus plantae (flexor

accessorius)

10 Tendon of flexor hallucis longus11 Flexor hallucis longus12 Flexor hallucis brevis13 Flexor digiti minimi brevis14 Tibial nerve

15 Medial plantar nerve16 Lateral plantar nerve17 Posterior tibial artery and veins18 Calcaneal (Achilles) tendon19 Gastrocnemius

A Sole of left foot superficial from belowB Sole of left foot first and second layer from belowC Left leg and sole of foot second layer from the right and below

Sole of foot 159

Location of numbers: 1ABC; 2BC; 3B; 4B; 5C; 6C; 7C; 8C; 9C; 10BC; 11C; 12B; 13B; 14C; 15BC; 16B; 17C; 18C; 19C.

Lower limb: anterior musclegroups

Knee extension

Quadriceps: vastus medialis (1), lateralis (2) andintermedius arise from the femur; rectus femoris (3)arises from the ilium and overlies intermedius. Theyinsert via the patella (4), into the tibial tuberosity (5)to extend the knee. Rectus femoris also flexes the hip(the kicking muscle). The lower fibres of medialis helpprevent lateral patellar dislocation. Sartorius (6), thelongest muscle in the body, passes from the anteriorsuperior iliac spine to the tibia. It flexes and externallyrotates the hip, while also flexing the knee to sit cross-legged. The femoral nerve (L2,3,4) supplies all thesemuscles (knee jerk L3,4). Rectus femoris, crossing twojoints, is more susceptible to injury. Quadriceps are essen-tial for knee stability and must not be allowed to waste fol-lowing joint injury or surgery.

Femoral triangle

The femoral triangle lies between sartorius, the medialborder of adductor longus (8) and the inguinal liga-ment (9). Its floor is formed by the hip flexors iliop-soas (10) and pectineus (11), which is also anadductor, and adductor longus. Its roof is fascia lata.From lateral to medial the triangle contains thefemoral nerve (12), artery (13), and vein (14), andthe femoral canal. The femoral sheath surrounds onlythe artery, vein and canal. The latter contains a lymphnode and fat. Abdominal contents may pass into thefemoral canal as a femoral hernia, visible inferior and lat-eral to the pubic tubercle.

The femoral artery gives profunda femoris, whichsends circumflex femoral arteries and perforatingbranches to supply the thigh muscles. There are impor-tant anastomotic vessels between branches of thefemoral arteries and the gluteal arteries. These may pro-vide collateral circulation following occlusion of the femoralartery. The femoral artery and vein pass into the subsar-torial canal and through the hiatus in adductor magnus.The femoral pulse is palpable at the mid-inguinal point(this is not the mid-point of the inguinal ligament), midwaybetween the anterior superior iliac spine and the pubicsymphysis, and the vein may be accessed just medially.

The femoral nerve (L2,3,4 posterior divisions)

passes posterior to the inguinal ligament, and immedi-ately divides into muscular and cutaneous branches. Itsupplies the skin of the anterior and medial thighbefore continuing as the saphenous nerve that passeswith the great saphenous vein (15) to supply the skinof the medial leg and medial border of the foot (L4).Both the saphenous nerve and the nerve to vastusmedialis pass under sartorius, but neither go throughthe adductor hiatus.

Lower limb anterior and lateral compartments

In the leg the anterior and lateral compartments con-tain muscles that arise from the tibia, fibula,interosseous membrane and surrounding fascia.Muscles that pass anterior to the ankle dorsiflex thefoot (and toes), whereas those passing behind plan-tarflex. Muscles that pass medially to attach to thetarsal and metatarsals invert at the subtalar joint andthose passing laterally evert. The functional impor-tance is lifting the foot and toes in walking and inkeeping the body upright over the foot.

Inversion – Tibialis anterior (22), deep fibular (per-oneal) nerve, L4,5.Dorsiflexion – Tibialis anterior, extensor hallucislongus (23) for the big toe and extensor digitorumlongus (24) for the remaining toes. The extensor ten-dons in the toes form an expansion similar to the fin-gers. The expansion receives lumbricals, interossei andextensor digitorum brevis (25). The dorsiflexors aresupplied by the deep fibular nerve (L4,5).Eversion (and plantarflexion) – Fibularis longus (26)and brevis (27), superficial fibular nerve (28) (L5,S1).

Damage to the common fibular (peroneal) nerve(L4,5,S1,2), at the fibular neck (car bumper, tight plastercast) results in foot drop (the foot falls into plantarflexionand inversion). The toes scuff the ground during walkingor the leg is lifted high by hip and knee flexion resultingin the foot hitting the ground with a slap. There is sensoryloss over the anterolateral leg and dorsum of the foot asthe deep fibular supplies the first cleft and the superficialfibular the remainder.

The anterior tibial artery, passing on theinterosseous membrane with the deep fibular nerve,comes superficial at the ankle and on the dorsum ofthe foot it is palpable as the dorsalis pedis pulse (29)between extensors digitorum and hallucis longus.

160 The Lower Limb

A

B

C

9

18 4

5

22

32

26 31

2227

28

24

23

21 20

30

252915

1920

21

23

24

6

16

17

8

153

1

2

1314

11

7

1012

Prox

LatM

D

Prox

LatM

D

Prox

LatM

D

1 Vastus medialis2 Vastus lateralis3 Rectus femoris4 Patella5 Tuberosity of tibia6 Sartorius7 Adductor brevis8 Adductor longus

9 External oblique aponeurosisbecoming inguinal ligament

10 Iliacus11 Pectineus12 Femoral nerve13 Femoral artery14 Femoral vein15 Great saphenous vein16 Iliotibial tract

17 Gracilis18 Tensor fasciae latae19 Medial malleolus20 Lateral malleolus21 Extensor retinaculum22 Tibialis anterior23 Extensor hallucis longus24 Extensor digitorum longus25 Extensor digitorum brevis

26 Fibularis (peroneus) longus27 Fibularis (peroneus) brevis28 Superficial fibular (peroneal)

nerve29 Dorsalis pedis artery30 Extensor hallucis brevis31 Soleus32 Gastrocnemius

A Left thigh (from the front)B Left lower limb structures

(from the front)C Left lower limb structures

(from the left)

Lower limb: anterior muscle groups 161

Location of numbers: 1A; 2A; 3A 4B; 5B; 6A; 7A; 8A; 9A; 10A; 11A; 12A; 13A; 14A; 15AB; 16A; 17A; 18A; 19B; 20BC; 21BC; 22BC; 23BC; 24BC; 25C;26C; 27C; 28C; 29C; 30C; 31C; 32C.

Lower limb: posterior musclegroups

The sciatic nerve and its tibial branch supply all thefollowing muscles, which fall into groups for hipextension, knee flexion, ankle and toe plantarflexion,and foot inversion.

Hip extension and knee flexion

The three hamstring muscles lie in the posterior aspectof the thigh, and arise from the ischial tuberosity.Biceps femoris (1) arises from the same tendon assemitendinosus (2), but has a second head from thelinea aspera of the femur. It passes to the head of thefibula, its attachment split by the lateral collateral lig-ament of the knee. Semitendinosus, the lower part ofits length being tendon, and semimembranosus (3),the upper part of its length being flat, membranoustendon, pass from the ischial tuberosity to the medialcondyle of the tibia.

The hamstrings extend the hip in walking and flexthe knee. They pass to either side of the knee joint,therefore, may rotate the flexed knee. As hamstringscross two joints, they are prone to injury. They are sup-plied by L5,S1,2 via the sciatic nerve. Therefore,L5,S1,2 are the root values for hip extension and kneeflexion.

Knee flexion and ankle plantarflexion

Gastrocnemius (8) is the most superficial, arising bytwo heads from the femoral condyles, passing into thecalf and converging into the calcaneal tendon (9),which inserts into the posterior aspect of the calca-neus. Soleus (10) lies deep to gastrocnemius. It arisesfrom the tibia and fibula and also converges into thecalcaneal tendon. The posterior tibial neurovascularbundle lies deep to soleus, which is visible as a linearbulge on the lateral calf in athletes. Gastrocnemiusand soleus plantarflex the ankle. Gastrocnemius,because it arises from the femur, also flexes the knee.The tibial nerve (12) (S1,2) supplies both muscles.

Plantaris is a variable muscle arising by a small bellyfrom the lateral femoral condyle and becoming a long,thin tendon lying medial to the calcaneal tendon andinserting into it, or into the calcaneus. It very weaklyassists gastrocnemius and has the same nerve supply.

Ankle, toe plantarflexion and inversion

Three muscles lie in the deep compartment and arisefrom the tibia, fibula and interosseous membrane.They form tendons, which pass in synovial sheaths,deep to a retinaculum behind the medial malleolus(13) where they are accompanied by the posterior tib-ial neurovascular bundle (14). The posterior tibial pulseis palpable midway between the heel and the medialmalleolus.

Tibialis posterior (15) lies immediately next to thetibia and medial malleolus. It inserts into many of thetarsal and metatarsal bones, but mainly the navicularand medial cuneiform. (Tibialis anterior inserts intomedial cuneiform and adjacent first metatarsal.)Tibialis posterior is a plantar flexor of the ankle and aninvertor of the subtalar joint. Its nerve supply is tibial(L4,5). (Tibialis anterior also not only inverts, butdorsiflexes.) Flexor digitorum longus (16) arises fromtibia only and has a tendon lying lateral to that of tib-ialis posterior as it passes around the ankle to enter thesole and run forward to the distal phalanges. Flexorhallucis longus (17) (mainly from fibula) lies deeply atthe ankle, with muscle fibres entering the tendon dis-tally. It passes into the sole and to the distal phalanx ofthe hallux.

The tibial nerve (S1,2) supplies flexors hallucis anddigitorum longus. The actions of all the posterior mus-cles are important in concert with the anterior and lat-eral groups, in walking, standing upright and balancingthe body over the ankle or angling the foot when walk-ing on uneven ground. Flexor hallucis longus is partic-ularly necessary for the final ‘push off’ in walking.Ankle and toe plantar flexion are essentially S1,2. Theankle jerk tests S1,2. Inversion is L4,5, whereas eversionis L5,S1.

162 The Lower Limb

A B C

4

220

8

11

12

7

3

2

8

10

18

9

17

1416

13

15

1

8

10

199

21 13

1

3

67

11 12

5

Prox

LatM

D

Prox

LatM

D

Prox

PA

D

1 Biceps femoris2 Semitendinosus3 Semimembranosus4 Gluteus maximus5 Iliotibial tract6 Popliteal artery

7 Popliteal vein8 Gastrocnemius9 Calcaneal (Achilles) tendon

10 Soleus11 Common fibular (peroneal) nerve12 Tibial nerve

13 Medial malleolus14 Posterior tibial artery and veins,

and tibial nerve15 Tendon of tibialis posterior16 Tendon of flexor digitorum

longus

17 Tendon of flexor hallucis longus18 Great saphenous vein19 Small saphenous vein20 Sural nerve21 Lateral malleolus

A Left gluteal region (from behind)B Left lower limb structures (from

behind)C Left leg structures (from the right)

Lower limb: posterior muscle groups 163

Location of numbers: 1AB; 2AB; 3AB; 4A; 5A; 6A; 7AB; 8BC; 9BC; 10BC; 11AB; 12AB; 13BC; 14C; 15C; 16C; 17C; 18C; 19B; 20B; 21B.

Buttock musculature, sciaticnerve

In the buttock, the sacrum (1) is medial, the greatertrochanter (2) lateral, and midway between the two isthe prominent ischial tuberosity (3). Structures pass-ing medial to the tuberosity, between it and thesacrum, are passing to the perineum. Structures pass-ing lateral to the tuberosity, between it and the greatertrochanter are passing to the posterior thigh.

Hip extension

The rounded shape of the buttock is created by sub -cutaneous fat overlying the musculature. The region isdivided (left, right) by the natal cleft. Gluteus maximus(4) arises from the posterior part of the ilium, the sacrumand sacrotuberous ligament (5). It inserts into the glutealtuberosity to provide powerful hip extension when run-ning, climbing stairs and standing from sitting. Maximusalso inserts into the iliotibial tract (6) with tensor fasciaelatae. Consequently it supports the knee close-packed inextension and helps gluteus medius and minimus holdthe pelvis level during walking. The iliotibial tract turnsthe lower limb into a strong, supportive strut for thebody. Maximus is supplied by the inferior gluteal vesselsand nerve (7) (L5,S1,2). There is a bursa allowing move-ment between it and the ischial tuberosity.

Hip abduction

Gluteus medius (8) and minimus (9) arise deep tomaximus, from the lateral aspect of the ilium.Minimus is covered by medius. Both insert onto thelateral aspect of the greater trochanter, medius poste-riorly and minimus anteriorly. Both muscles are pow-erful abductors of the hip but their important functionis to work in concert with the adductors and the ili-otibial tract to prevent pelvic tilt during walking.Medius and minimus, along with tensor fasciae lataeare supplied by the superior gluteal vessels and nerve(10) (L4,5,S1).

Hip lateral rotation

Inferomedial to gluteus medius, piriformis (11) passesfrom the inner aspect of the sacrum, to the tip of thegreater trochanter. Obturator internus (12), from theinternal aspect of the obturator membrane, and obtura-

tor externus, from the external aspect of the membrane,pass to the medial aspect of the greater trochanter.Internus has the superior (13) and inferior (14) gemellilying parallel to its tendon. Quadratus femoris (15)passes from the ischial tuberosity to the quadrate tuber-cle on the intertrochanteric crest of the femur.

All these muscles pass behind the hip joint thereforelaterally rotate it. When the lower limb swings for-ward during walking, so does the pelvis on the sameside. Lateral rotation of the femur ensures that thelower limb and foot are pointing forward. Branches ofthe lumbosacral plexus, ranging from L4 to S2 supplythe muscles.

Nerves in the buttock

There are a number of small, named nerves within thebuttock, passing to the overlying skin of the buttockand the perineum. They are branches of the glutealnerves and lumbosacral plexus and their root valuesrange from L4 to S4. The posterior femoral cutaneous(16), (S1,2,3) supplies branches to the perineum, andskin of the posterior thigh to just below the knee.

The sciatic nerve (17) (L4,5,S1,2,3) is formedwithin the pelvis from L4,5 (the lumbosacral trunk),and the ventral rami of S1,2,3. It emerges into thebuttock via the greater sciatic foramen, usually inferiorto piriformis and passes into the thigh. As it does so,the sciatic lies posterior to the hip joint, then midwaybetween the ischial tuberosity and the greatertrochanter. Intramuscular injections must be given in thesuperolateral quadrant of the buttock, well away from thesciatic nerve.

The nerve passes deep to biceps femoris (18), to lieburied between it and semitendinosus (19). It suppliesthe hamstrings and also sends a branch to adductormagnus (20), augmenting the latter’s supply from theobturator nerve. In the popliteal fossa the sciatic dividesinto tibial (21) and common fibular (22) branches. Thesite of the division is very variable, occurring anywherebetween the buttock and the popliteal fossa.

The tibial nerve (L4,5,S1,2,3 anterior divisions)passes inferiorly more or less in the middle of thepopliteal fossa, superficial to the artery and vein. Itpasses deep to gastrocnemius and soleus, which it sup-plies and runs with the posterior tibial artery in thefascial septum that separates the superficial from thedeep muscular compartment.

164 The Lower Limb

A B

C

4

6

18

16

19

18 19 20

25

20

5

3 24

4

1

11

8

2

46

15

14 17171616

5

26

1312

25

24

4

1

17

9

8

8

82 7

11

2723

26

1110

5

3

4

6

2221

Prox

MLat

D

Prox

MLat

D

Prox

MLat

D

1 Sacrum2 Greater trochanter of femur3 Ischial tuberosity4 Gluteus maximus5 Sacrotuberous ligament6 Iliotibial tract7 Inferior gluteal artery, vein and

nerve

8 Gluteus medius9 Gluteus minimus

10 Superior gluteal artery, vein andnerve

11 Piriformis12 Obturator internus13 Superior gemellus14 Inferior gemellus

15 Quadratus femoris16 Posterior femoral cutaneous

nerve17 Sciatic nerve18 Biceps femoris19 Semitendinosus20 Adductor magnus21 Tibial nerve

22 Common fibular (peroneal)nerve

23 Internal pudendal artery24 Levator ani25 External anal sphincter26 Pudendal nerve27 Inferior rectal artery, vein and

nerve

A Left gluteal region (from behind)B Left gluteal region (from behind)C Left gluteal region (from behind)

Buttock musculature, sciatic nerve 165

Location of numbers: 1BC; 2BC; 3BC; 4ABC; 5BC; 6ABC; 7B; 8BC; 9B; 10B; 11BC; 12C; 13C; 14C; 15C; 16AC; 17BC; 18AB; 19AB; 20BC; 21A; 22A; 23B;24BC; 25BC; 26BC; 27B.

Blood vessels

The abdominal aorta passes behind the median arcu-ate ligament of the diaphragm at the level of T12. Itsupplies the undersurface of the diaphragm via theinferior phrenic arteries that also send superiorsuprarenal arteries to the suprarenal gland. The aortagives the middle suprarenal arteries, whereas the infe-rior suprarenals arise from the renal arteries. Lumbararteries arise from the aorta to supply the abdominalwall, and they also send spinal arteries through theintervertebral foramina to augment the blood supplyto the spinal cord. Occlusion of these may cause cordischaemia.

The coeliac trunk (axis) arises at the level of T12 andsupplies the structures derived from the embryologicalforegut. The superior mesenteric artery (SMA) arisesat L1 to supply structures derived from the midgut.The left and right renal arteries to the kidneys andadrenals arise at L2, with the gonadal arteries arisingjust below. The inferior mesenteric artery (IMA), tohindgut derived structures, arises at L3. The aortadivides at L4 into the common iliac arteries.

The coeliac trunk arises from the front of the aorta,between the diaphragmatic crura, above the pancreasand behind the lesser sac. It divides into the left gas-tric, splenic and (common) hepatic arteries. The leftgastric artery passes on the diaphragm to where theoesophagus pierces it. The artery divides and sends abranch up through the diaphragm to anastomose withthe oesophageal branches from the thoracic aorta tosupply the lower third of the oesophagus. The left gas-tric continues into the lesser omentum to run alongthe lesser curvature of the stomach. The splenic arterytakes a tortuous course behind the pancreas, andpasses with it, in the lienorenal ligament, to supply thespleen. It sends short gastrics in the gastrosplenic liga-ment to supply the fundus of the stomach, the leftgastro-epiploic to supply the greater curvature of thestomach and greater omentum, and the greater pan-

creatic artery to the pancreas. The (common) hepaticartery passes to the right, lifts off the posterior abdom-inal wall to enter the free edge of the lesser omentumand passes to the liver as the hepatic artery. The (com-mon) hepatic gives the right gastric and the gastroduo-denal. The latter divides into the right gastro-epiploicand the superior pancreaticoduodenal.

There is an anastomotic ring of vessels around thestomach, and free anastomosis in the duodenumbetween branches of the coeliac trunk and SMA. TheSMA arises behind the pancreas and (with its vein)passes between the neck and uncinate process of thepancreas, anterior to the duodenum (third part),behind the transverse mesocolon and into the mesen-tery to supply the midgut. It supplies the pancreas andduodenum via the inferior pancreaticoduodenal arteryand the transverse colon via the middle colic. In themesentery the SMA gives jejunal and ileal branches toform arcades within the mesentery. Near its termina-tion it sends right colic arteries to the ascending colon,and the ileocolic to the ileum, caecum and appendix.The appendicular artery arises from the posterior cae-cal branch of the ileocolic.

The IMA passes to the left, behind the peritoneumto supply the hindgut. It sends left colic and sigmoidbranches to the descending and sigmoid colon. It endsas the superior rectal that passes into the pelvis toanastomose with the middle and inferior rectal arter-ies and supply the rectum and anal canal. Within thecurve of the large bowel, the right colic, middle colicand left colic arteries anastomose with each other toform the marginal artery. Slow occlusion of the IMA byan aortic aneurysm allows a collateral circulation to openvia the marginal artery.

The inferior mesenteric vein is the continuation ofthe superior rectal vein from the rectum and analcanal. They are also drained by middle and inferiorrectal veins to the internal iliac, therefore the lowerrectum and anal canal are sites of portosystemic anas-tomosis. The inferior mesenteric vein passes up the

Appendix to abdomen and pelvis:structures and concepts not visibleon illustrations

Appendix to abdomen and pelvis 167

posterior abdominal wall, medial to the left gonadalvein and ureter. It usually enters the splenic vein,behind the pancreas, but may enter the superiormesenteric vein or the portal vein directly.

Lymph nodes and vessels lie on the anterior and lat-eral surfaces of the aorta. These converge to form thecisterna chyli that passes behind the median arcuateligament (to the right of the aorta), to continue as thethoracic duct. The part of the gastrointestinal tract sup-plied by a particular artery sends lymph back to the nodeson the aorta around that artery.

Autonomic innervation

The splanchnic nerves arise from the sympathetictrunk in the thorax and pass through the crura of thediaphragm to converge on a plexus of nerves and gan-glia around the coeliac trunk, SMA and IMA. Thegreater splanchnic (T5–9) synapses in the coeliacganglia, to be distributed with branches of the coeliactrunk to all foregut structures. The lesser splanchnic(T10,11) synapses in the superior mesenteric ganglia,to be distributed with the SMA to all the midgut, aswell as to the gonads via the gonadal arteries. The leastsplanchnic (T12) synapses in the inferior mesentericganglia to be distributed to the hindgut with branchesof the IMA.

Below the IMA the plexus continues downward onthe front of the aorta as the pre-aortic plexus. Theplexus is augmented by lumbar splanchnics, whicharise in the L1,2 segments of the cord, and whichemerge from the lumbar part of the sympathetictrunk. The pre-aortic plexus passes over the pelvicbrim as the superior hypogastric nerve and divides intothe left and right pelvic plexuses or inferior hypogas-tric nerves. Sympathetic (thoracolumbar) innervationis generally to slow down intestinal function by shut-ting sphincters and decreasing peristalsis, to divertenergy for ‘fight or flight’.

Parasympathetic (craniosacral) efferents are to pro-mote digestive function by opening sphincters andincreasing peristalsis. These are from the vagus nerves,which enter the abdomen with the oesophagus and aredistributed as far as two-thirds along the transversecolon via the coeliac and superior mesenteric plexuses.The hindgut receives parasympathetic innervation

arising from S2–4 and passing via the pelvic plexuses,up the superior hypogastric nerve to reach the inferiormesenteric plexus, for distribution with the IMA.

Referred pain

The sympathetic nerves all have afferent fibres run-ning with them. These transmit the signals of visceralpain and distension back to the cord segments fromwhich they arise. The brain cannot localize visceralpain and perceives it as arising from the skin of theequivalent dermatome in the midline i.e. visceral,referred pain.

All foregut pain refers to the epigastrium, i.e. the T5–9dermatomes. Midgut (including appendix) and gonadalpain refers to the T10,11 dermatomes around theumbilicus. An embryological remnant, Meckel’s diverticu-lum, is said to be 5 cm (two inches) long and occurs intwo-thirds of people and originates 0.6 m (two feet) fromthe end of the ileum. It may become inflamed and thepain mimics that of appendicitis. Hindgut pain refers tothe T12 dermatome that is suprapubic. Once an inflamedor distended viscus affects the overlying parietal peri-toneum, the pain is localized, as the parietal peritoneumis sensitive and supplied by the same nerves that supplythe overlying skin.

Inguinal canal

During embryonic development the testis migratesdown the posterior abdominal wall, through the ante-rior wall and into the scrotum. It carries the vas, thetesticular neurovascular supply and the processus vagi-nalis (an extension of the peritoneal cavity) with it.The tunnel through the anterior abdominal wallremains as the inguinal canal. In the female it trans-mits the round ligament of the uterus.

In the male the testis, vas and testicular vessels ‘pickup’ the layers of spermatic fascia that form the sper-matic cord as they pass the abdominal fascia and mus-cles. Transversalis fascia provides the internalspermatic fascia. The conjoint tendon provides the cre-master muscle and cremasteric fascia. The externaloblique muscle provides the external spermatic fasciato complete the spermatic cord as it leaves theabdomen. The terminal branches of the ilio-inguinalnerve commence deep to the external spermatic fascia.

The cremaster muscle receives the artery to cremas-ter (from the inferior epigastric) and its sympatheticnerve supply is with the genital branch of the gen-itofemoral nerve (L1,2) that reaches it via the deepinguinal ring. Cremaster helps dartos retract the testis.The cremaster reflex is mediated by L1 and is testicularretraction following stroking of the skin on the uppermedial thigh.

The spermatic cord, comprising the three layers ofspermatic fascia, contains:● vas deferens with its artery to the vas, derived from

the inferior vesical.● testicular artery, from the aorta at L2, and carrying

sympathetic efferents, and afferents derived fromthe lesser splanchnic nerve (T10,11) to the testis.

● pampiniform plexus of veins that coalesces to formthe testicular vein. The left testicular vein drains, atright angles, into the left renal vein and this may causea varicocele, a tortuous dilatation of the pampiniformplexus, visible and palpable through the scrotal skin.Left-sided varicoceles also raise the suspicion of left-sided renal tumours that have invaded the renal vein.

Testicular lymph drainage is to the para-aortic nodes.Therefore testicular tumours will spread to these para-aortic nodes. The inguinal nodes are only involved if thetesticular tumour spreads to the scrotum.

The inguinal canal tunnels through, or under theabdominal-wall muscles ensuring that the two open-ings of the tunnel, the deep and superficial rings, aresupported and protected by two of the muscles. Thedeep inguinal ring is just above the mid-point of theinguinal ligament, midway between the pubic tubercleand anterior superior iliac spine. The femoral arterypasses below the inguinal ligament a little medially atthe mid-inguinal point, midway between the pubicsymphysis and the anterior superior iliac spine. Thedeep ring is an opening in the transversalis fascia. It liesjust lateral to the inferior epigastric artery and justmedial to the lowest fibres of transversus abdominis asthey arise from the inguinal ligament and curve overthe canal, to form its roof, then its posterior wall, asthe conjoint tendon. (Opinions differ on the positionof the deep ring and some authors place it at the mid-inguinal point.)

The aponeurosis of external oblique and the musclefibres of internal oblique are anterior to the deep ring.Half to two-thirds of the way along the inguinal liga-

ment the internal oblique fibres then curve over thecanal, to contribute to its roof and then to its posteriorwall as the conjoint tendon. The superficial (external)ring is a triangular opening in the external obliqueaponeurosis. The base is on the pubic crest. The apexis above and lateral to the pubic tubercle. The edges ofthe ‘ring’ are the medial and lateral crura, supportedwhere they meet at the apex of the triangle by inter-crural fibres of external oblique aponeurosis. The con-joint tendon, as it attaches to the pubic crest andpecten lies behind the superficial ring, to protect andsupport it.

The inguinal canal has:● A floor – inguinal ligament● A roof – transversus abdominis and internal oblique● An anterior wall – external and internal oblique lat-

erally, only external oblique medially● A posterior wall – transversalis fascia laterally, both

internal oblique and transversus abdominis, fused asthe conjoint tendon, medially.

Scrotum

In the scrotum, the testis, epididymis and vas appearto invaginate into an extension of the peritoneal cav-ity, the tunica vaginalis from behind so that a viscerallayer of mesothelium covers them. Posteriorly, in thespermatic cord, this visceral layer reflects to becomethe parietal layer, leaving an intervening potentialspace with a little serous fluid. Initially, in the infant,this potential space communicates with the peritonealcavity, but that connection should obliterate com-pletely to leave the processus vaginalis in the sper-matic cord. If it does not obliterate, abdominal contentsmay herniate into the processus and consequently intothe scrotum. Partial obliteration may leave cysts.

The parietal layer is itself surrounded by the threelayers of spermatic fascia. The parietal layer of tunicavaginalis and the three spermatic fascias of each testisfuse in the middle of the scrotum to form a septum.Consequently, the testis is effectively suspended in thescrotum, within a potential space between the parietaland visceral layers of the tunica vaginalis. Occasionallythe testis may rotate within this space, twisting and there-fore compromising the blood supply. This condition, tor-sion of the testis, must be recognized and surgically

168 Appendix to abdomen and pelvis


treated within about five hours, before the testis becomesnecrotic. The potential space within the tunica vaginalismay fill with fluid, a hydrocele. Embryological remnantsleave little appendices on the epididymis and upper poleof the testis. These may become painfully inflamed.

Superficial fascia of the penis andscrotum

Penile superficial fascia has a membranous inner layer(Buck’s fascia) that is continuous with Scarpa’s fasciain the lower anterior abdominal wall and upper thigh.Posteriorly, this fascia is continuous with the superfi-cial fascia of the scrotum (Colles’) that attaches to thepubic bones, ischiopubic rami, and perineal body inthe midline, just anterior to the anal opening. Thissuperficial fascia forms the superficial boundary of thesuperficial perineal pouch.

Pelvic fractures and/or urethral rupture may causebleeding and extravasation of urine that is held within thefascial space deep to this membranous layer of fascia. Theconsequent bruising is visible on the lower abdomen,upper thighs, penis and scrotum, but stopping just ante-rior to the anus.

Hernias

Weaknesses in the anterior abdominal wall may allowthe development of a hernia, which is prolapse orextrusion of abdominal contents, from small tags of fat, toloops of bowel.

Inguinal hernias appear at the superficial ring abovethe pubic tubercle. They may enter the scrotum.● Indirect inguinal – usually in young males, some-

times with a patent processus vaginalis. The herniapasses into the deep ring, lateral to the inferior epi-gastric artery, and down the inguinal canal. Oncereduced, such hernias maybe controlled by the exam-ining surgeon applying pressure on the skin over thesite of the deep ring.

● Direct inguinal – occurring as a result of generalweakness in the abdominal muscles or conjoint ten-don. The hernia pushes into the inguinal canal,straight through the posterior wall, or pushing theposterior wall in advance of it. It occurs in the

inguinal triangle, bounded inferiorly by the inguinalligament, laterally by the inferior epigastric arteryand medially by the lateral edge of rectus abdo-minis. Consequently a direct hernia is medial to theinferior epigastric artery, whereas an indirect herniais lateral. The fibres of internal oblique and transversusabdominis that form the conjoint tendon are suppliedby the iliohypogastric nerve (L1). This nerve may beinjured during appendicectomy, possibly leading to aweakness of the conjoint tendon and consequentinguinal herniation.Umbilical hernias. The umbilicus is the puckered

scar left on the abdominal wall by the embryonicumbilical cord that contained the umbilical vein andarteries, the urachus and the vitello-intestinal duct.Hernias may extrude through the umbilicus or just toone side of it (para-umbilical).

Incisional hernias follow failure of muscle closurepost operatively. Every attempt is made when incisingthe abdomen to prevent damage to the neurovascularsupply and to avoid cutting muscle fibres. The pre-ferred route is to separate the muscle fibres in theirdirection. Incisions through the avascular linea albamay facilitate rapid access, but healing may be difficultdue to that avascularity. Paramedian incisions arethrough the rectus sheath, and then reflecting rectusabdominis.

Femoral hernias are more common in the female,with the wider pelvis, and are through the femoralcanal, between the lacunar ligament and femoral vein,posterior to the inguinal ligament. They appear belowand lateral to the pubic tubercle and are more likely toincarcerate.

Lumbar hernias occur posteriorly (and very rarely)in the triangle between the free posterior edge ofexternal oblique, latissimus dorsi and the iliac crest.

Pelvic peritoneum

The peritoneum dips inferiorly from the abdomen tocover the organs in the pelvis, creating a continuousabdominopelvic, peritoneal cavity. From anterior toposterior the peritoneum covers the bladder, then theuterus and uterine (Fallopian) tubes with the vesico-uterine pouch between, and then the rectum, with therecto-uterine pouch between. The peritoneum passes

down the anterior abdominal wall, onto the superiorand posterior surfaces of the bladder. As a result thebladder is inferior to the peritoneal cavity and as it fillsit extends upward, pushing the peritoneum upwardwith it.

Urinary obstruction (usually caused by prostatic hyper-trophy in the male) causes the bladder to extend up intothe abdomen. It always pushes the peritoneum and theorgans within the peritoneal cavity upward and behind it,so that the bladder lies immediately posterior to the ante-rior abdominal wall. If necessary, a suprapubic cathetermay be safely passed through the abdominal wall, justabove the pubic symphysis, and into the bladder to drainit.

The recto-uterine pouch (of Douglas) is the lowest pointin the abdominopelvic cavity. Blood, fluid or pus maydescend into it. At this point the peritoneum lies on theupper, posterior aspect of the vagina, its posterior fornix.The recto-uterine pouch may be surgically drained via thevagina. But instruments used ineptly in abortions maypierce the posterior fornix and enter the peritoneal cavity,possibly introducing severe infection.

In either sex, the lower third of the rectum lies com-pletely outside the peritoneal cavity and does not haveperitoneum on it at all. But peritoneum clothes theanterior surface of its middle third, and the anteriorsurface and sides of its upper third.

Pelvic ligaments (female)

The uterine tubes have the appearance of havingpushed upward into the peritoneal cavity to create afold of peritoneum with anterior and posterior layersthat pass laterally to reach the pelvic wall. The twolayers form the broad ligament. The anterior layercontinues as the peritoneum on the anterior abdomi-nal wall. The posterior layer continues as the peri-toneum on the posterior abdominal wall. As a result,the ovarian neurovascular bundle passes down theposterior abdominal wall and enters the lateral aspectof the broad ligament to create the suspensory liga-ment of the ovary.

In the embryo, the ovary forms on the posteriorabdominal wall, and migrates into the pelvis, guidedby the gubernaculum, which remains as the ligamentof the ovary and the round ligament of the uterus. Theround ligament of the uterus passes laterally from theuterus, in the broad ligament, to reach the anterior

abdominal wall and enter the deep inguinal ring. It isthought to hold the uterus in its normal antevertedand anteflexed position. The ligament of the ovaryattaches the ovary to the side wall of uterus.

In the female, as the ovary is truly intraperitonealand the ovum is secreted into the peritoneal cavity,the infundibulum pierces the posterior leaf of thebroad ligament so that the fimbriae overhang the ovaryin the peritoneal cavity. This anatomical arrangementmeans that in the female, the peritoneal cavity is effec-tively open to the exterior via the vagina, uterus anduterine tubes. Foreign matter may enter the peritonealcavity by this route. To prevent this, the epithelium andmucous membrane of the tube are highly folded andthe folds interdigitate with each other. The uterinecavity is very narrow and mucous membrane folds inthe cervix also interdigitate with each other. The ante-rior and posterior walls of the vagina are normallyopposed to each other. Rarely, it is possible to overridethis protective, safety mechanism.

Anal continence and defecation

Faeces remains in the sigmoid colon before descendinginto the rectum where its distending presence isdetected by afferents in the parasympathetic systemand the desire to defecate is initiated.

The circular layer of smooth muscle in the wall ofthe intestinal tract thickens as the internal anal sphinc-ter that is under autonomic control and ends at thewhite line (intersphincteric groove). The puborectalisportion of levator ani sweeps around the recto-analjunction. Its contraction pulls the junction forward,making the angle between the rectum and anal canalmore acute, helping to hold faeces in the rectum. Theexternal anal sphincter, of striated muscle, encirclesthe anal canal, in three parts, the deep, superficial andsubcutaneous. The superficial part not only encirclesthe anal canal like the others, but also attaches to theanococcygeal ligament and the perineal body.

Fibres of puborectalis fuse with fibres of the deeppart of the external sphincter and with fibres of theinternal sphincter to form the anorectal ring, which isnecessary for continence and is palpable on rectal exam-ination. During defecation puborectalis and the exter-nal sphincter relax under the influence of the perineal

170 Appendix to abdomen and pelvis


branches of S3,4 and the inferior rectal branches of thepudendal nerve (S2,3,4). The colon contracts and theinternal sphincter relaxes, under parasympathetic con-trol that also arises from S2,3,4. The abdominal wall isvoluntarily contracted to raise the intra-abdominalpressure.

Micturition, erection and ejaculation

The bladder fills by paying-out under the parasympa-thetic control of detrusor. Usually at about 310 mLthere is a desire to micturate. The sensation is carriedmainly by parasympathetic afferents, but painful stim-uli are via sympathetics.

With simultaneous contraction of the abdominalwall, the parasympathetic supply via the pelvicsplanchnics (S2,3,4) causes detrusor contraction andurine enters the urethra. In the male, the sympathetic

supply to the internal urethral sphincter is over-rid-den, so it relaxes. The sensation of urine in the urethrais via the pudendal nerve (S2,3,4) and this sensationmaintains the micturition reflex. This is an example ofinvoluntary and voluntary reflexes working together atS2,3,4.

During erection, the parasympathetic system is alsosaid to over-ride the sympathetic supply to the penilearteries, causing them to dilate and the penis tobecome erect. But at ejaculation the sympathetic takesover causing some contraction of the muscular compo-nents of the reproductive ducts and closure of theinternal urethral sphincter to prevent backflow ofsemen to the bladder. The pudendal nerve and itsbranches contain sympathetic fibres from the pelvicplexus, and parasympathetic fibres from the sacralsplanchnics (S2,3,4). Erection is under parasympa-thetic control, but ejaculation is sympathetic.

Books

Ellis H, Logan BM, Dixon AK (1999) HumanSectional Anatomy: Atlas Of Body Sections, CT andMRI Images. 2nd edn. Oxford: Butterworth-Heinemann.

Federative Committee on Anatomical Terminology(1998) Terminologia Anatomica – InternationalAnatomical Terminology. Stuttgart: Thieme.

Logan BM, Reynolds P, Hutchings RT (2004)McMinn’s Colour Atlas of Head and Neck Anatomy,3rd edn. London: Mosby.

Logan BM, Singh D, Hutchings RT (2004) McMinn’sColour Atlas of Foot and Ankle Anatomy, 3rd edn.London: Mosby.

McMinn RMH, Gaddum-Rosse P, Hutchings RT,Logan BM (1995) McMinn’s Functional and ClinicalAnatomy. London: Mosby-Wolfe.

Moore K, Dalley AF (1999) Clinically OrientatedAnatomy, 4th edn. Baltimore, MD: Lippincott,Williams & Wilkins.

Romanes GJ (ed) (1981) Cunningham’s Textbook ofAnatomy, 12th edn. Oxford: Oxford UniversityPress.

Sinnatamby CS (ed) (1999) Last’s Anatomy Regionaland Applied, 10th edn. Edinburgh: ChurchillLivingstone.

Standring S (ed) (2005) Gray’s Anatomy, 39th edn.London: Elsevier Churchill Livingstone.

Other resources

Dyball R (Cambridge), Davies CD (St George’s),McHanwell S (Newcastle), Morris JF (Oxford),Parkin IG (Cambridge), Whiten S (St Andrew’s),Wilton J (Birmingham). Setting a benchmark foranatomical knowledge and its assessment (A corecurriculum for the teaching of anatomy to medicalstudents, available at: www.anatsoc.org.uk).

Bridger John (2006) Revision anatomy for clinical stu-dents. Cambridge: Department of Anatomy,University of Cambridge.

Bibliography

www.anatsoc.org.uk

The majority of references are to core structures. Page numbers are almost all for left hand (text) pages ofeach double page spread. Readers can assume that they will find the structure on the facing right hand (illus-trated) page. Non-core anatomical structures have generally not been indexed. The exception is to the appen-dix section (on abdominal and pelvic structures and concepts not visible in illustrations) and these pagenumbers are in italics.

Index

abdomen 85–105, 166–71full 86organs 86

abdominal wallanterior 104muscles 102, 104, 128, 168

external oblique 82, 104, 128, 167, 168posterior 101, 102

abducent nerve (VI) 28, 34abduction

definition 5fingers and thumbs 2, 3, 140hip 4, 164shoulder 2, 134wrist 2, 3

abductor(s), hip 152abductor digiti minimi

foot 158hand 142, 145

abductor hallucis 158abductor pollicis brevis 142, 145abductor pollicis longus 138accessory (spinal) nerve (X) 28, 54accessory parotid lobe 44acetabular labrum 152acetabulum, rim 152Achilles (calcaneal) tendon 162acoustic meatus

external 20, 30internal 22, 30

acromioclavicular joint 8acromion 8adduction

definition 5fingers and thumbs 2, 3, 140hip 4, 152shoulder 2, 134

adductor brevis 152adductor longus 152, 160adductor magnus 164adductor pollicis 144

adenohypophysis (anterior pituitary) 22adenoid 38adrenal (suprarenal) gland 94, 98, 100air cells of paranasal sinuses 36alveolar nerve, inferior 40anal canal 108, 120, 170

lower end (anal orifice/anus) 110anal continence 170–1anatomical planes 1anatomical snuffbox 136ankle (joint) 156

movements 4, 5, 162anococcygeal ligament 108anterior triangle of neck 55antrum of stomach 88anular ligament of radius 136anus see entries under analaorta 70, 80

arch 64ascending 64, 70, 80descending

abdominal 90, 166thoracic 64

lymph nodes and vessels on surfaces of 167aortic valve 80aponeurosis

bicipital 132, 138epicranial 42palmar 132, 142plantar 156, 158

appendicular skeleton 8appendix, vermiform 92arachnoid mater (brain) 24, 26arcuate line 10, 105areola 82arterial supply

abdominal organs 88, 90, 96brain 26face 44lower limb 158, 160nasal cavity/nasopharynx 38

arterial supply – contdneck 58upper limb 132see also specific arteries

articular discs see discsarticular facets, superior 14articular tubercle of temporal bone 20aryepiglotticus 52arytenoid cartilages 50

muscular process 50arytenoid muscle

oblique 52transverse 52

atlas, lateral mass 14atria

left 74, 76right 74, 76septum between 76

atrioventricular node 78auditory tube (Eustachian tube) 38

groove for 20auricles

atria, left and right 80ear 30

auricular nerve, greater 44auriculotemporal nerve (V3) 30auscultation

of heart 78triangle of 128

autonomic innervation, abdominopelvic 167erection/ejaculation and 171micturition and 171

axial skeleton 8axilla 132, 146axillary artery 58, 146axillary lymph nodes 132axillary nerve 134, 146axillary vein 132, 146azygos vein 66, 70

Bartholin’s gland 110basilar artery 26biceps (brachii) 132

long head 138short head 138, 147tendon 138

biceps (femoris) 162, 164bicipital aponeurosis 132, 138biliary tree/system/ducts 90, 96bladder (urinary) 116

base 114, 116female 116function 171male 116, 118neck 114, 118

blood supplyabdominal organs 88, 90, 92, 96

brain 26external genitalia 110, 112face 44lower limb 160

foot 158nasal cavity/nasopharynx 38neck 58upper limb 132see also arterial supply; venous drainage and specific

vesselsbody, parts of 1bone 8

orbit 32skull 20upper limb 8–9see also skeleton

bowel (intestine) 90brachial artery 132, 146brachial plexus 146

posterior/lateral/medial cords 146brachiocephalic trunk 58brachiocephalic veins, right and left 66brachioradialis 136, 140brain 26brain stem 24breast 82broad ligament of the uterus 124, 170

posterior leaf 122Broca’s speech area 26bronchi 72

left main 65, 72, 80right main 72

bronchopulmonary segments 72buccal branches of facial nerve 44buccinator 42bulb

olfactory 26, 38of penis 118of vestibule 110

bulbospongiosus muscle 112bulla ethmoidalis 36bursae, prepatellar 154buttock muscles 164

caecum 86, 92calcaneal tendon 162calcaneocuboid joint 156calcaneus 10, 156calcarine sulcus 26calyces, minor and major 98cardiac region of stomach 88cardiac vein, great 80cardio-oesophageal junction 88carotid arteries 58

common 60left 64right 58

174 Index

Index 175

external 53, 58, 61internal 26, 58

carotid canal 20carpus 8cartilage(s) 8

costal 8, 64, 68ethmoid 36laryngeal 50septal 36tracheal 50

cauda equina 16caudate lobe of liver 94caval vein see vena cavacavernosal body (corpora cavernosa) 112central sulcus 26central tendon

diaphragm 70, 74perineum (perineal body) 110, 124

cephalic vein 132cerebellum 24, 26cerebral aqueduct 26cerebral arteries 26cerebral hemispheres 24cervical branches of facial nerve 44cervical fascia and spaces 54cervical vein, transverse 58cervical vertebrae 14cervicothoracic (stellate) ganglion 66cervix, uterine 116, 124, 170cheek bone (zygomatic arch) 40chest see thoraxchewing/mastication, muscles 40, 42, 46chordae tendineae 78ciliary ganglion 34circumflex branch of coronary artery 80circumflex humeral arteries, posterior 134circumvallate papillae 46clavicle 8, 56, 58, 68, 128, 132

medial part 54clitoris 112

prepuce 110clivus 23coarse hair (nose) 36coccygeus 108coccyx 10, 108coeliac trunk/plexus 70, 166, 167colon 12

descending 98haustrations/sacculations 90transverse 86, 90

commissure, posterior (labia majora) 110communicating artery, posterior 26conducting system of heart 78condylar canal 20condyles

femoral 154occipital 20

conjunctiva 30constrictors

inferior 2superior and middle 48

coracobrachialis 138coracoid process 8corona of glans penis 112coronary arteries

left 80right 80

coronary ligaments, lower 94coronary sinus 76, 80coronoid process

mandible 40ulna 136

corpus callosum 26corpus cavernosa 112corpus spongiosum 112, 118cortex, renal 98costal cartilages 8, 64, 68costodiaphragmatic recess 70cranial nerves 28

see also specific nervescranium see skullcremaster muscle 168cribriform plate of ethmoid 22, 36, 38cricoarytenoid muscle, posterior 52cricoid cartilage, lamina and arch 50cricopharyngeus 48cricothyroid 52cricothyroidotomy site 50crista galli 22crista terminalis 76, 78cruciate ligaments, anterior and posterior 154crus

clitoris 113diaphragm 70

cubital vein, median 132cuboid 10, 156cuneiform bone 156cusps

aortic valve 80mitral valve 78pulmonary valve 80tricuspid valve 78

cutaneous nerves of thigh (femoral cutaneousnerves)

lateral 102posterior 164

cystic artery 96cystic duct 96

dartos muscle 110, 168deep fascia, forearm 132defecation 170–1deltoid ligament 156deltoid muscle 128, 132, 134, 147

Denonvillier’s fascia 114dens 14dental (alveolar) nerve, inferior 40dentition 46diaphragm 70, 88

central tendon 70, 74crus 70domes 70movements 70relations 70structures passing through/behind 70

digastric muscle 42digit movements

lower limb 4, 5, 162upper limb 2, 3, 138, 140

digital branchesmedian nerve 144ulnar nerve 142

dilator muscles of oral cavity 42discs (fibrocartilaginous/articular)

inferior radio-ulnar joint 136intervertebral see intervertebraltemporomandibular joint 40

dorsal arteryfoot (dorsalis pedis artery) 161penis 112

dorsal interossei 144dorsal nerve, penis 112dorsal root ganglion 16dorsal rootlets 16dorsal vein, penis 112dorsiflexion 5, 160, 162Douglas’ pouch 116, 170ductus (vas) deferens 114, 118, 167, 168duodenum 86, 90, 94, 100dura mater

brain 20spinal cord 16

ear 30ejaculation 171elbow 136

movements 2, 138, 140epicondyle, medial (humerus) 136epicranial aponeurosis 42epididymis 168

head/body/tail 114epidural space 16epigastric artery, inferior 104, 114epigastric vein, inferior 104, 114epigastrium 86epiglottis 50erection 171ethmoid bone 22, 32, 35

cribriform plate 22, 36, 38ethmoid cartilage 36ethmoidal bullae 36

ethmoidal sinus/air cells 34, 36Eustachian tube see auditory tubeeversion

definition 5foot 5, 160

extensiondefinition 5lower limb 4, 5

ankle (dorsiflexion) 5, 160, 160hip 4, 162, 164knee 160

upper limbdigits 140elbow 2shoulder 2wrist 2, 3, 140

extensor carpi radialis brevis 140extensor carpi radialis longus 140extensor carpi ulnaris 140extensor digiti minimi 140

split tendon 140extensor digitorum brevis 160extensor digitorum longus 160extensor digitorum muscle 140extensor expansions 140extensor hallucis longus 160extensor indicis 140extensor pollicis brevis 140extensor pollicis longus 138extensor retinaculum

lower limb 150upper limb 140

eyelashes 32eyelids 32

faceneurovascular supply 44skeleton and muscles 42

facets, superior articular 14facial artery 44facial nerve (VII) 28

buccal branch 44cervical branch 44marginal mandibular branch 44temporal branch 44zygomatic branch 44

facial vein 44faecal (anal) continence 170–1falciform ligament 86, 94Fallopian (uterine) tubes 122, 170falx cerebri 24

free/inferior margin 24fascia

cervical 54lower limb 150obturator 108penis and scrotum 169

176 Index

Index 177

pharyngobasilar 48rectofascial 114rectovesical (Denonvillier’s) 114thoracolumbar 128upper limb 132

fatbreast 82perirenal 98

fauces, pillars of 46femoral artery 160, 168femoral canal 160femoral cutaneous nerves see cutaneous nerves of thighfemoral hernia 169femoral nerve 150, 160femoral triangle 160femoral vein 150, 160femur 8, 154

condyles 154greater trochanter 152, 164head 152

ligament of 152neck and shaft 152

fibrocartilaginous discs see discsfibrocartilaginous menisci (knee) 154fibrous bands see tendinous intersectionsfibrous capsule of hip joint 152fibrous flexor sheath, fingers 138, 142fibula 8, 156fibular (peroneal) nerve

common 150, 164superficial 160

fibular (peroneal) retinaculum 150fibularis (peroneus) brevis 160fibularis (peroneus) longus 160

groove 10fimbriated end of uterine tube 122finger movements 2, 3, 138, 140flexion

definition 5lower limb 4, 5

ankle (plantarflexion) 5, 160, 162hip 4, 152knee 162

upper limbdigits 3, 138elbow 2, 138shoulder 2wrist 3, 138

flexor accessorius 158flexor carpi radialis 132, 138flexor carpi ulnaris 138flexor digiti minimi brevis

foot 158hand 142

flexor digitorum brevis 158flexor digitorum longus 158, 162flexor digitorum profundus 138, 144

tendon 138flexor digitorum superficialis 138, 142flexor hallucis brevis 158flexor hallucis longus tendon 156, 158flexor pollicis brevis 138, 142flexor pollicis longus 138flexor retinaculum

lower limb 150upper limb 132, 142

flexor sheath, fingers 138, 142foot

arches 154ligaments 10movements 4, 5, 160sole 158

forameninfra-orbital 32intervertebral 14jugular 20, 22optic (optic canal) 22, 32sciatic, lesser 108stylomastoid 20

foramen cecum 22foramen lacerum 20, 22foramen magnum 16, 20, 22foramen ovale 20, 22foramen spinosum 20, 22forearm 136

deep fascia 132movements 2, 3, 138, 140muscles 138, 140

foreskin, penis 112fossa(e)

cranial 22glenoid 134iliac, right and left 86ischio-anal 108mandibular 20piriform (recess) 50pituitary 22popliteal see popliteal fossatrigeminal (trigeminal impression) 32

fossa ovalis 76frontal bone 30, 35, 36

orbital part 32frontal eye field 26frontal lobe 26frontalis 42fundus

gall bladder 96stomach 88

fungiform papillae 46

gall bladder 86, 94, 96fundus/body/neck 96

ganglionciliary 34

ganglion – contddorsal root 16geniculate 30stellate 66trigeminal 28

gastric artery, left 166gastrocnemius 162gastro-esophageal (cardio-oesophageal) junction 88gemelli, inferior and superior 164geniculate ganglion 30genioglossus 46geniohyoid 46genitalia

externalfemale 110, 112, 116male 110, 112

internal (incl. gonads)female 122, 124, 170male 114, 118, 167–8

genitofemoral nerve 100, 168glans penis 112

rim/corona 112glenohumeral joint 134glenoid fossa 134glenoid labrum 134glossopharyngeal nerve (IX) 28, 46gluteal vessels and nerves

inferior 164superior 164

gluteus maximus 164gluteus medius 153, 164gluteus minimis 153, 164gonad(s) see genitalia, internal; ovary; testiclegonadal veins 100gracilis 152granulations, arachnoid 24gyrus

postcentral 26precentral 26

hair see coarse hair; eyelasheshallux, phalanges 157hand

deep palm 142superficial palm 142

haustrations of colon 90head and neck 19–45heart 74–81

apex 74auscultation 78blood supply 80chambers 76conducting system 78in situ and removed 74superior and external views 80surface projections of four corners 74valves 76, 78, 80

hepatic artery 96, 166hepatic duct

common 96left and right 96

hernia, abdominal 169hiatus semilunaris 36hilar lymph nodes 72hip abductors 152hip bones 8hip joint 152

fibrous capsule 152movements 4, 152, 162, 164

horizontal plate of palatine bone 20humerus 8

greater tuberosity 134head 134trochlea 136

hyaline cartilagecostal 8, 68trachea 50

hyoid bone 46, 50, 56hypochondrium, left and right 86hypogastrium (suprapubic region) 86hypoglossal nerve 46hypoglossus 44, 46

ileum 86, 92iliac artery

common 100internal 116, 118, 120, 124

iliac fossa, right and left 86see also inguinal region

iliac spines, anterior superior 10, 104iliac vein, internal 116, 118, 120, 124iliacus 102ilio-inguinal nerve 102iliopsoas 152, 160iliotibial tract 150, 164incisional hernia 169infrahyoid (strap) muscles 56infra-orbital foramen 32infra-orbital groove 32infundibulum of uterine tube 122inguinal canal 167–8inguinal hernia 169inguinal ligament 104, 150, 160inguinal region (iliac region) 86

lymph nodes 150inguinal ring

deep 168superficial 104, 168

interatrial septum 76intercostal artery, posterior 64intercostal muscles 68

internal 82intercostal vein, left superior 64interossei (foot) 158

178 Index

Index 179

interossei (hand)dorsal 144palmar 144

interventricular artery, anterior 80interventricular groove 76interventricular septum 76, 78intervertebral discs 8, 14

lumbar 16intervertebral foramen 14intestine 90inversion

definition 5foot 5, 160, 162

ischial spine 10ischial tuberosity 10, 108, 164ischio-anal fossa 108ischiocavernous muscle

clitoris 112penis 112

ischiopubic rami 10, 108

jejunum 86, 98jugular foramen 20, 22jugular vein

external 54, 60internal 54, 60

kidney 70, 90, 98capsule 98cortex 98medulla 98neurovascular supply 98relations 98right 94

knee joint 154movements 4, 160, 162

L1/L2 disc, lumbar spine 16labia majora 110labrum

acetabular 152glenoid 134

lacrimal bones 32lacrimal mechanism 30lacrimal nerve 34lacrimal sac 32lactiferous ducts 82laminae

cricoid cartilage 50vertebral 14

laryngopharynx 48larynx 50

muscles 52lateral cutaneous nerve of thigh 102lateral malleolus 150, 156lateral plantar nerve 158lateral plate of pterygoid process 20

lateral rotationhip 5, 164shoulder 2, 134

latissimus dorsi 128, 132, 147levator anguli oris 42levator ani 108, 120, 170–1

females 117, 125males 115, 118

levator depressor oris 42levator labii superioris 42levator palati 38, 48levator palpebrae superioris 34levator scapulae 54ligaments

ankle 156foot 10knee 154pelvic 170temporomandibular joint 41see also specific ligaments

ligamentum patellae 155ligamentum teres (femoris; ligament of femoral head) 152ligamentum teres (hepatis) 94limbs see lower limb; upper limblinea alba 104, 128lingual artery 46lingual nerve 40, 46lingual tonsil 48lingula, left lung 72Little’s area 38liver 70, 86, 94

bare area 94lobes 86, 94, 96peritoneum and spaces surrounding 94relations 94

loin 86lower limb 10, 149–65

movements 4–5lumbar hernia 169lumbar region 86lumbar spine

intervertebral discs 16vertebrae 14

lumbrical musclesfoot 158hand 144

lunate 136lung 72

apex 58fissures 72hilum 64, 72lobes 72

lower, apical segment 72relations 72

lymphatic system (vessels/nodes/trunks)abdomen 90, 167anorectal 120

lymphatic system (vessels/nodes/trunks) – contdaxilla 132breast 82neck 60popliteal fossa/inguinal region 150testes 168thorax 72

McBurney’s point 104malar arch (zygomatic arch) 40malleolus

lateral 150, 156medial 150, 156, 162

mammary artery, internal 58mammary ducts (lactiferous ducts) 82mandible 8, 20, 23, 46

angle 44coronoid process 40head 40neck 40

mandibular fossa 20mandibular nerve (V3) 28manubriosternal joint 8manubrium 54, 56marginal artery 80marginal mandibular branch of facial nerve 44masseter 40, 44mastication/chewing, muscles 40, 42, 46mastoid antrum 30mastoid process 20, 30maxilla 32, 35, 36, 46maxillary artery 40maxillary nerve (V2) 28, 30, 38maxillary sinus 36medial collateral ligament (ankle) 156medial epicondyle (humerus) 136medial malleolus 150, 156, 162medial meniscus 154medial plantar nerve 158medial plate of pterygoid process 20medial rotation

hip 4shoulder 2, 134

median cubital vein 132median nerve 132, 138, 142, 146

digital branches 144mediastinum

from left 64from right 66lung relations to other structures 72

medulla, renal 98medulla (oblongata) 16, 26membranes, laryngeal 50membranous urethra 118meningeal arteries

anterior and posterior branches 20middle branches 22

meningesbrain 24spinal cord 16

meniscus, medial 154mentalis 42mesenteric artery

inferior 166, 167superior 90, 166, 167

mesenteric vein, inferior 166–7mesentery 86, 90, 92, 102metacarpal arteries 144metacarpal bones 8

first 8metatarsal bone 8, 156

first 157micturition 171midcarpal joints 136midtarsal joints 156milk (lactiferous) ducts 82mitral valve, cusps and papillary muscles 78modiolus 42mons pubis 110motor neurones, brain 26mouth see oral cavitymovements

diaphragmatic 70lower limb 4–5

foot 4, 5, 160hip 4, 152, 162, 164knee 4, 160

temporomandibular joint 40upper limb 2–3

digits 2, 3, 138, 140elbow 2, 138, 140shoulder 2, 132wrist 2, 3, 138, 140

musclesabdominal wall see abdominal wallfacial 42lower limb 150, 154, 158, 160, 162, 164masticatory/chewing 40, 42, 46neck

infrahyoid muscles 56laryngeal muscles 52

oral cavity 42, 46orbital 34pelvic floor 108thoracic 68, 70upper limb 132, 138, 140see also specific muscles

muscular process of arytenoid cartilage 50musculocutaneous nerve 138, 146mylohyoid 44, 46

nasal air sinuses (paranasal sinuses) 36ethmoid sinus 34, 36

nasal bones 35, 36

180 Index

Index 181

nasal cavity 36neurovascular supply 38

nasal conchae/turbinates 23, 36nasal meati 36nasociliary nerve 34nasolacrimal duct 32, 36nasopharynx 38, 48

neurovascular supply 38navicular 10, 156neck 50–61

anterolateraldeep 58, 60superficial 54

nerves/nerve supplyabdominopelvic

autonomic see autonomic innervationkidney 98liver 96

buttock 164cranial 28ear 30external genitalia 110, 112face 44foot 158heart 74nasal cavity/nasopharynx 38neck 58, 60oral cavity 46orbital 34see also specific nerves

neurohypophysis (posterior pituitary) 22nipple 82nose see entries under nasal

oblique arytenoid muscle 52oblique fissure of lung 72oblique muscles of abdomen

external 82, 104, 128, 167, 168internal 104, 168

oblique muscles of eyeinferior 34superior 34

obturator fascia 108obturator internus 108, 164occipital bone 35

condyles 20occipital lobe 24, 26occipital protuberance, internal 24occipitalis 42, 44oculomotor nerve (III) 28, 34odontoid peg 14oesophagogastric (cardio-oesophageal) junction 88oesophagus 66, 70, 88, 94olfactory bulb 28, 38olfactory nerves 38olfactory tract 28omentum, greater 86

omohyoid muscle 56ophthalmic nerve (V1) 28opponens digiti minimi 142optic canal/foramen 22, 32optic chiasma 28optic nerve 28oral cavity 46

muscles 42, 46orbicularis oculi

orbital part 32palpebral part 32

orbicularis oris 42orbit

muscles 34nerves 32skeleton 32

orbital fissuresinferior 32superior 22, 32

orbital plates 22oropharynx 46, 48oval fossa (fossa ovalis) 76ovarian artery 122ovarian vein 124ovary 122, 170

pain, referred 167from heart 74

palatehard 46soft 46, 48

palatine bone 23horizontal 20, 36perpendicular plate 20

palatine nerve, greater 38palatine tonsil 48palatopharyngeus 48palm

deep 144superficial 142

palmar aponeurosis 132, 142palmar arches, deep 144palmar arteries 144palmar interossei 144palmaris brevis 142palmaris longus 138, 142palpebral part of orbicularis oculi 32pancreas 90, 92

head/neck/body 92tail 92, 98uncinate process 92

papillary musclesmitral valve/left ventricle 78tricuspid valve/right ventricle 78

paranasal sinuses see nasal air sinusesparasympathetic innervation, abdominopelvic 167

erection and 171

parasympathetic innervation, abdominopelvic – contdmicturition and 171

parathyroid gland 56parietal bone 35parietal lobe 26parotid duct 44parotid gland 44

accessory lobe 44patella 154, 160

bursae in region of 154patellar ligament 155pectinate muscles (of atria; musculi pectinati) 76pectineal line 10pectineus 152, 160pectoralis major 82, 128, 132, 147pectoralis minor 128, 132, 147pelvic floor

female 124male 114muscles 108

pelvic tilt prevention 152pelvis (pelvic region) 107–25, 166–71

female 110, 112, 116, 122, 124male 110, 112, 114, 118skeleton/pelvic girdle 10

pelvis (renal) 98penis 112

bulb 118erection 171glans of see glans penissuperficial fascia 169

pericardium (pericardial sac) 64, 70, 74perineum 108

body 110, 124periosteum 42perirenal fat 98peritoneum 86, 116

pelvic 169–70perihepatic, and spaces 94

peroneal (fibular) nerve see fibular nerveperoneal (fibular) retinaculum 150peroneus (fibularis) muscle see fibularis brevis; fibularis

longusperpendicular plates of palatine bone 20petrosal nerve, greater 30petrosal sinuses, superior 24petrous temporal bone 20, 22

mastoid process 20phalanges

foot 156hand 8

pharyngeal raphe 48pharyngeal tonsil 38pharyngobasilar fascia 48pharynx 48

laryngeal part (laryngopharynx) 48nasal part see nasopharynx

oral part (oropharynx) 46, 48phrenic nerve

left 60, 64right 66

pia mater 24pinna (auricle) 30piriform fossae (recess) 50piriformis 108, 164pituitary fossa 22pituitary gland 16, 26, 36planes, anatomical 1plantar anatomy 158plantar aponeurosis 156, 158plantar nerve, medial and lateral 158plantar quadrate muscle (quadratus plantae; flexor

accessorius) 158plantarflexion 5, 160, 162platysma 42pleural cavities 68plicae circulares 90pons 26, 28popliteal fossa 10

lymph nodes 150popliteal vein 150popliteus 154porta hepatis 96portal vein 90, 96portosystemic anastomoses 88postcentral gyrus 26posterior triangle of neck 55precentral gyrus 26prepatellar bursae 154prepuce

clitoris 110penis 112

prevertebral muscles 60pronation

definition 5forearm 2, 3, 138

pronator quadratus 138prostate gland 114, 118, 120prostatic urethra 118psoas major 70, 100, 102

see also iliopsoaspterion 20pterygoid

lateral 40medial 40

pterygoid process, medial and lateral plates 20pterygomaxillary fissure 30pubic bones 10

body 10crest 10, 128tubercle 10, 104

pubic symphysis 8, 10, 108, 116, 128puborectalis 170–1pudendal neurovascular bundle 108

182 Index

Index 183

pudendal nerve 108, 171pulmonary artery/trunk 74

left 65, 72, 80right 72, 80

pulmonary valve 80pulmonary vein

inferior 72left 65, 76

superior 72left 65, 76

pylorus, gastric 88pyramid, renal medullary 98

quadrate lobe of liver 94, 96quadratus femoris 164quadratus lumborum 70, 102quadratus plantae (flexor accessorius) 158quadriceps 160

tendon 154

radial artery 132, 137, 138, 144radial nerve 146radio-ulnar joints, superior and inferior 136radius 8

anular ligament 136capitulum 136distal head 137head 136

rectal neurovascular bundle, inferior 108recto-uterine pouch 116, 170rectovesical fascia 114rectum 120, 170

female 124male 114

rectus abdominis 104, 128sheath of 104, 128

rectus femoris 160rectus muscles of eye 34renal artery 98renal pelvis 98renal vein 98

left 100reproductive organs see genitaliarespiration, thoracic wall in 82retinacula see extensor retinaculum; fibular retinaculum;

flexor retinaculumrhomboids 128ribs 68

first 8, 58heads/tubercles/necks/shafts 68

rotation 4definition 5shoulder 2, 134see also lateral rotation

round ligament of the uterus 124rugose scrotal skin 110

sacculations of colon 90sacroiliac joints 10sacrospinous ligament 10, 108sacrotuberous ligaments 10, 108, 164sacrum 8, 10, 120, 164

promontory 10sagittal sinus, superior 24salivary glands 44salpingopharyngeus 38, 48saphenous vein

great 150small 150

sartorius 150, 160scalenus (scalene muscles)

anterior 58, 60medius and posterior 54

scalp 42scaphoid 8, 136scapula 8sciatic foramen

greater and lesser 10lesser 108

sciatic nerve 164scrotum 168–9

rugose skin 110superficial fascia 169

sella turcica 22semilunar hiatus 36semimembranosus 154, 162seminal vesicles 114, 120semitendinosus 162, 164sensory neurones, brain 26septal cusp of tricuspid valve 78septum

interatrial 76interventricular 76, 78nasal, cartilage 36

serratus anterior 82, 128, 132, 147shoulder, movements 2, 132shoulder joint 134sigmoid sinuses, right and left 24sinu-atrial node 78skeleton 7–11

face 42orbit 32thorax 68see also bone

skinscalp 42scrotal, rugose 110

skull (cranium) 8anterior/medial/posterior fossa 22base 20–4bones 20–4

sole of foot 158soleus 162spermatic cord 168

spheno-ethmoidal recess 36sphenoid bone 35, 36

body 20, 22greater wing 22, 32lesser wing 22, 32

sphenoidal sinus 36sphenopalatine artery 38sphincters

analexternal 170internal 171

urethral see urethral sphincterspinal arteries, posterior 16spinal column (vertebral column) 16, 90spinal cord 16spinal nerves 16

accessory (X) 28, 54spinous process 14splanchnic nerves 167

greater 66spleen 70, 88, 98

notch 92splenic vessels 98, 166

splenic artery 88, 92splenic vein 92

splenius capitis 54spongy urethra 118squamous temporal bone 20, 22, 35stellate ganglion 66sternoclavicular joint 8sternocleidomastoid 44, 54sternohyoid 56sternothyroid 56sternum 8

manubrium of 54, 56stomach 70, 86, 88, 90, 94, 98

arterial supply 88cardia/fundus/body/antrum/pylorus 88greater curvature 88lesser/upper curvature 88

straight sinus 24strap muscles 56styloid process 20, 44stylomandibular ligament 40stylomastoid foramen 20subclavian artery 58, 60

branches 58left 64right 58

subclavian vein 60subhepatic space, left and right 94sublingual gland 44sublingual papilla 44submandibular duct 44, 46submandibular gland 44submucosal folds, intestinal 90subphrenic space, left and right 94

subscapularis 134, 147sulcus

calcarine 26central 26terminal 46

supinationdefinition 5elbow/forearm 2, 3, 138, 140

supra-orbital nerve 34suprapatellar bursa 154suprapubic region 86suprarenal gland 94, 98, 100suprascapular vein 60supraspinatus 134supratrochlear nerve 34sural nerve 150suspensory ligaments

breast 82clitoris 112uterus 122

sustentaculum tali 10sympathetic innervation/chain/trunk

abdominopelvic region 167ejaculation and 171micturition and 171

mediastinum 66neck 60

symphysis pubis (pubic symphysis) 8, 10, 108, 116, 128

taenia coli 90talofibular ligament, anterior 156talus 10, 156

head 156tarsal bones 8tarsal joints 156teeth 46temporal bone

articular tubercle 20petrous part see petrous temporal bonesquamous part 20, 22, 35styloid process 20, 44

temporal branch of facial nerve 44temporal lobe 26temporalis 40, 42temporomandibular joint 20, 40temporomandibular ligament, lateral 40tendinous intersections (fibrous bands)

extensor tendons of fingers 140rectus abdominis 128

tensor palati 38tentorium cerebelli 24, 28

free edge/margin 24teres major 128, 134, 146teres minor 134terminal crest (crista terminalis) 76, 78terminal sulcus 46testicles (testes) 114, 167, 168, 168–9

184 Index

Index 185

testicular artery 168thigh, cutaneous nerves see cutaneous nervesthoracic artery

internal 58, 64lateral 146

thoracic duct 64, 70thoracic inlet 58thoracolumbar fascia 128thoracolumbar innervation 167thorax 63–83, 128

skeleton 68wall in respiration 82

thumbabduction and extension 140flexion 138

thymus 64, 68thyroid artery

inferior 58superior 56

thyroid cartilage 50notch 50superior horn 50

thyroid gland 56isthmus 56

thyroid vein, superior and inferior 56thyropharyngeus 48tibia 8, 150, 154, 156

plateau 154shaft 155tuberosity 160

tibial artery, posterior 158, 163tibial nerve 150, 154, 158, 162, 164

posterior 163tibial neurovascular bundle, posterior 162tibial vein, posterior 163tibialis anterior 160tibialis posterior 162tibiofibular joint 156toe movements 4, 5, 162tongue 46tonsils 38, 48tooth 46torso (trunk) 128

movements 4trabeculae carneae 76trachea 50, 58, 66trachealis 50tracheostomy site 50transversalis fascia 86, 104transverse arytenoid muscle 52transverse cervical vein 58transverse colon 86, 90transverse fissure of lung 72transverse process 14

foramina 14transverse sinuses 24transversus abdominis 102, 104

trapezius 54, 128triangle(s)

of auscultation 128neck

anterior 55posterior 55

urogenital 110triangular ligaments, left and right 94triceps 140

long head 134tricuspid valve 76, 78trigeminal impression 22trigeminal nerve (V) 28

ganglion 28trochlea of humerus 136trochlear nerve (IV) 28, 34trochlear pulley of superior oblique 34trunk see torsotubal eminence (of auditory tube) 38tubal tonsil 38tunica albuginea 112, 114tunica vaginalis 168, 169tympanic membrane 30

ulna 8, 136head 137

ulnar artery 144ulnar nerve 136, 138, 142, 144, 146

deep branch 144digital branches 142

umbilical region 86hernia 169

umbilicus 104, 128uncinate process 92upper limb 131–47

movements see movementsmuscles 132, 138, 140skeleton 8–9

ureter 116, 118female 116, 118, 122, 124male 114, 118

urethra 108female 116male 112, 114, 118opening 110

urethral sphincterexternal 118internal 171

urinary bladder see bladderurination (micturition) 171urogenital triangle 110uterine (Fallopian) tubes 122, 170uterus 124, 170

neck (cervix) 116, 124, 170uvula 48

vagina 116, 124, 170

vagina – contdbulb of vestibule 110opening 110

vagus nerve (X) 28, 58left 58, 64right 66

valve (cardiac) 76, 78, 80vas (ductus) deferens 114, 118, 167, 168vascular supply see blood supply; lymphatic systemvastus lateralis 160vastus medialis 160vena cava

inferior (IVC) 70, 76, 90, 94, 100superior 66, 74, 76, 78, 80

venous drainageface 44lower limb, superficial 150neck 60upper limb 132see also specific veins

ventral rami 16ventral rootlets 16ventricles (cardiac)

left 64, 76papillary muscles 78

right 74, 76papillary muscles 78

septum between 76, 78ventricles (cerebral)

fourth 26lateral 26third 26

vermiform appendix 92vertebra(e) 8, 14

body/pedicles/laminae 14discs between see intervertebral discs

vertebral arteries 26vertebral column 16, 90vestibular fold 50vestibular gland, greater 110vestibule (vagina), bulb of 110vestibulocochlear nerve (VIII) 28vocal fold/cord 50

false 50true 50

vomer 20, 36

wrist (joint) 136movements 2, 3, 138, 140

zygomatic bone 30arch 40

zygomatic branch of facial nerve 44zygomatic muscles 42

186 Index

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