APS1 Notes

8/12/2019 APS1 Notes

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SKELETAL SYSTEM

CLASSIFICATION OF BONES - 206

Axial skeleton

Long axis of the body Skull, vertebral column, rib cage Most involved in protecting, supporting, carrying other body parts

Appendicular skeleton

Upper and lower limbs, girdles (shoulder/hip bones) that attach limbs toaxial skeleton

Involved in locomotion and manipulation of environmentClassified by shape

Long bones longer than they are wideo Shaft + 2 endso All limb bones except patella, wrist + ankle bones

Short bones approximately cube shapedo Wrist and ankles

Flat boneso Thin, flattened, usually a bit curvedo Sternum, scapulae, ribs, most skull bones

Irregular boneso Complicated shapeso Vertebrae, hip bones

Bone development

In uteroo Derived from mesenchymeo Development

Postnatalo Growth

Formation of the bony skeleton

Before week 8, skeleton entirely fibrous membranes + hyaline cartilage Intramembranous ossification bone developing from fibrous membrane

o Membrane bone Endochondral ossification bone development by replacing hyaline

cartilage

o Cartilage/endochondral bone


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Intramembranous ossification

Results in formation of cranial bones + clavicleso Frontal, parietal, occipital, temporal

Most are flat bones ~Week 8 of development, ossification begins on fibrous CT membranes

derived from mesenchyme

4 major steps of intramembranous ossification

Ossification centres appear in fibrous CT membraneo Mesenchymal cells differentiate osteoblasts

Bone matrix (osteoid) is secreted within fibrous membrane and calcifieso Osteoblasts secrete osteoido Trapped osteoblastsosteocytes

Woven bone + periosteum formo Osteoid accumulates between/around blood vessels randomly

results in network of woven boneo Vascularised mesenchymeperiosteum

Lamellar bone replaces woven bone, red marrow appearso Trabeculae deep to periosteum thicken later replaced with

mature lamellar bone, forming compact bone plates

o Spongy bone remains and vascular tissue red marrowEndochondral ossification

Almost all bones form by this method From 2ndmonth of development, hyaline cartilage bones used as models

for bone construction

More complex than intramembranous because hyaline cartilage must bebroken down as ossification proceeds

Primary ossification centre centre of hyaline cartilage shaft Secondary ossification centre one or both epiphyses gain bony tissue Structure

o Diaphysiso Epiphysiso Medullary cavity lined with endosteum

Filled with yellow marrowo Outer covering periosteum

Double membrane Outer fibrous layer DICT for strength Connect to compact bone by Sharpeys fibres Internal membrane osteogenic layer

Osteoblasts Osteoclasts Osteogenic cells

Vascular and innervatedo Compact bone

Osteons

Lamellae


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Harversian system (central canal) Volkmanns canals (perforating canals) connect

blood/nerve supply of periosteum to other canals

Lacunae/osteocyteso Spongy bone

Trabeculae, filled with red or yellow marrowOSSIFICATION

Conversion of hyaline cartilage to bone

PRIMARY diaphysis SECONDARY epiphyses FINAL epiphyseal plates

Postnatal bone growth

Long bones lengthen entirely by interstitial growth of epiphyseal platecartilage + its replacement by bone

Cartilage cells at the top growth/proliferation zoneo Divide quickly, pushing the epiphysis away from diaphysis entire

long bone lengthens

Older cells enlarge surrounding cartilage matrix calcifies chondrocytesdiecalcification zone

Bone growth ends with epiphysis and diaphysis fuse epiphyseal platecloser

o ~18 in femaleso ~21 in males

Can continue to grow in width


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Foetal skeleton

Ossificaion of skull starts late in second month of development At birth, skull bones sill incomplete connected by fontanelles

o Allow infants head to be compressed slightlyBONE REMODELLING AND REPAIR

Bone remodeling

Comprise bone deposit and resorption Bone deposit where bone is injured or requires extra strength by

osteocytes

Bone resorption osteoclastsControl of remodeling

Negative feedback maintaining Ca2+ homeostasis Reponses to mechanical/gravitational forces

Hormonal controls

Parathyroid hormone (PTH) parathyroid glandso Secretes when low blood Ca2+ levelso Stimulate resorption of bone osteoclasts break down bone

Calcitonin much more minimal effectMechanical stress

Muscle pull + gravity Wolffs law bone grows/remodels in response to demands placed on it

o Bone anatomy reflects common stresses Loading usually off centre bends bone (tension)

o As a result, bone usually thickest in middleHOMEOSTATIC IMBALANCES OF BONE

Osteomalacia and Rickets

Inadequate mineralization of bones Osteoid produced but calcium salts not deposited soften and weaken

bones

Painful when weight put on affected bones Osteomalacia in adults Rickets in children much more severe because bones are still growing Often caused by insufficient calcium in diet or vit D deficiency

Osteoporosis

Bone resorption > bone deposit bone mass decreasesbecome porousand light

Spongy bone of spine most vulnerable Most often occurs in the aged


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CRANIUM

8 cranial bones: parietal + temporal (2 each) Frontal, occipital, sphenoid, ethmoid Brains protective helmet

Frontal Bone Anterior cranium Articulates posteriorly

o Paired parietal bones via coronal suture Forehead vertical squamous part

o Ends inferiorly at supraorbital margins Forms superior margins of the orbits + most of the anterior cranial fossa

o Supraorbital margins pierced by supraorbital foramen supraorbital artery + nerve passes to forehead

Glabella between orbitso Lateralfrontal sinuses

Frontonasal suture joins nasal to frontal boneParietal bones + major sutures

One on each side, separated by sagittal suture Form most of the superior/lateral aspects of the skull bulk of cranial

vault

Major sutures:o Coronal parietalfrontalo Sagittal parietalcranial midlineo

Lambdoid parietal

occipitalo Squamous patietaltemporal


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Occipital bone

Forms most of skulls posterior wall + base Articulates anteriorly with: parietal, temporal bones via: lambdoid +

occipitomastoid sutures

Joins with sphenoid bone in cranial floor via basilar region Forms posterior cranial fossa Foramen magnum at base inferior part of brain connects with spinal

cord

Occipital condylesarticulate with atlasTemporal bones

Located under parietal bones articulate at squamous sutures 4 regions

o Squamous Zygomatic process

o Tympanic Surrounds external acoustic meatus Styloid process

o Mastoid Mastoid process Stylomastoid foramen

o Petrous Deep Cranial base middle cranial fossa Middle/internal ear cavities Jugular foramen, carotid canal Foramen lacerum Internal acoustic meatus

Sphenoid bone Consists of central body + 3 pairs of processes

o Greater wingso Lesser wingso Pterygoid processes

Sphenoid sinuses Superior sella turcica

o Seat hypophyseal fossa Houses pituitary gland

Greater wings project laterally and formo Middle cranial fossao Dorsal walls of orbitso External wall of skull

Lesser wings formo Part of the anterior cranial fossao Medial walls of orbits

Pterygoid processes project inferiorlyo Anchor pterygoid muscles chewing muscles


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Openings of the sphenoid bone

Optic canals Superior orbital fissure Foramen rotundum/ovale/spinosum

Ethmoid bone Deepest skull bone Forms most of bony area between nasal cavity + orbits Superior formed by cribriform plates

o Help form roof of nasal cavitieso Anterior cranial fossao Punctured by tiny holes olfactory foraminao Crista galli superior process

Secures brain in cavity Perpendicular plate

o Forms superior part of nasal septum divides nasal cavity intoleft/right halves Lateral masses with ethmoid sinuses

o Superior nasal conchae Lateral surfaces of lateral masses orbital plates

o Medial walls of orbitsFACIAL BONES

Mandible

U-shaped Largest, strongest facial bone Ramus meets body at angle Two processes separated by mandibular notch Coronoid process at anterior Mandibular condyle at posterior

o Articulates with mandibular fossa of temporal bone Body anchors lower teeth alveolar margin = sockets Mental foramina

Maxillary bones

Upper jaw/central portion of facial skeleton Articulates with all facial bones except mandible Carry upper teeth in alveolar margins Palatine processes bony roof of mouth

o Project posteriorly from teeth Frontal processes lateral nose bridge Lateral to nasal cavity maxillary sinuses Articulate with zygomatic bones via zygomatic processes Inferior orbital fissure at junction of maxilla with greater wing of

sphenoid

Infraorbital foramen below eye socket


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Zygomatic bones

Cheekbones Articulate with zygomatic processes of

o Temporal boneso Frontal boneo Maxillae

Cheeks and part of inferolateral orbital marginsNasal bones

Fused medially forms bridge of nose Articulate with frontal bone, maxillae, perpendicular plate of ethmoid

bone, cartilages of external nose

Lacrimal bones

Contribute to medial walls of each orbit Articulate with:

o Frontal bone superiorlyo Ethmoid bone posteriorlyo Maxillae anteriorly

Contains deep groove forms lacrimal fossao Houses lacrimal sacallows tears to drain from eye surface into

nasal cavity

Palatine bones

L shapedo Horizontal + perpendicular plates

Articular processeso Pyramidalo Sphenoidalo Orbital

Horizontal platesjoined medially, form posterior part of hard palate Perpendicular plates form posterolateral walls of nasal cavity + small part

of the orbits

Vomer bones

Forms inferior part of the nasal septumInferior nasal conchae

Thin, curved bones in the nasal cavity Project medially from lateral walls of nasal cavity

o Inferior to middle nasal conchae of ethmoid bone Form lateral walls of nasal cavity

Hyoid bone

Lies inferior to mandible in anterior neck Only bone that does not articulate directly with any other bone Horseshoe-shaped


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Special characteristics of the orbits and nasal cavity

The Orbits

Encases eyes, cushioned by fatty tissue Also contains muscles that move the eyes + lacrimal glands Consists of seven bones

o Frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal andethmoid bones

Superior/inferior orbital fissues + optic canals also seenNasal Cavity

Constructed of bone and hyaline cartilage Roofcribriform plates of ethmoid Lateral wallslargely superior/middle conchae of ethmoid bone,

perpendicular plates of palatine bones + inferior nasal conchae

Floorpalatine processes of maxillae + palatine bones Divided into right + left parts by nasal septum

o Vomer inferiorly, perpendicular plate of ethmoid superiorlyParanasal sinuses

Mucosa-lined, air-filled cavities that cluster around the nasal cavity Five skull bonesfrontal, sphenoic, ethmoid + pairedmaxillary (2)

sinuses

Air enters sinuses from nasal cavity mucus formed by sinus mucosaedrains into nasal cavity

Mucosa helps to warm/humifidy inspired air

Lighten the skull + enhance resonance of the voiceHuman skull

Larger cranial case, especially frontal bone (bigger brain = greaterintelligence), smaller snout (less dependency of smell), smaller mandible

(hunter/gatherer diet, omnivores vs herbivores), large orbits and

protected (greater reliance on vision)

THE VERTEBRAL COLUMN

26 irregular bones connected to provide curvature and flexibilityo 7 cervical (neck)o 12 thoracic (middle)o 5 lumbar (back)o COMMON MEAL TIMES 7am, 12noon, 5pm

Become progressively larger from cervical lumbar must supportgreater weight

Inferior to lumbar vertebrae sacrumo Articulates with hip bones of the pelviso Terminuscoccyx

Curvaturessinusoid (S) shape from lateral view (posterolateral)o Increase resilience + flexibility of spine Acts like spring rather than rod


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o Cervical + lumbar concaveo Thoracic + sacralconvex

Abnormal spinal curvatures

Scoliosis Abnormal lateral curvature Most often in thoracic region

Kyphosis

Dorsally exaggerated thoracic curvature Hunchback

Lordosis

Accentuated lumbar curvature Can arise from potbellies and pregnant women

o Adjustment to preserve centre of gravityIntervertebral discs

Cushionlike pad Two parts

o Inner gelatinous nucleus pulposusrubber ball Elasticity + compressibility

o Collar composed of collagen fibres + fibrocartilage annulusfibrosus

Limits expansion of nucleus pulposus when spine iscompressed

Withstands twisting forces + resists tension in spineHerniated (prolapsed)/slipped disc

Usually involves rupture of the annulus fibrosus followed by protrusion ofnucleus pulposus through annulus

o Can press on spinal cord/spinal nervenumbness/excruciatingpain

GENERAL STRUCTURE OF VERTEBRAE

Body/centrum anteriorly

o Disc shapedo Weight-bearing region

Vertebral arch posteriorly formed by:

Two pediclesshort bony pillarso Project posteriorly from bodyo Form sides of archo Inferior + superior notches provide lateral openings between

adjacent vertebraeintervertebral foramina (spinal nerves)

Two laminaeflattened plateso Form posterior part of arch


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Body + vertebral arch enclose vertebral foramen

Successive vertebral foramenvertebral canal (spinal cord)Seven processes project from vertebral arch

Spinous process arises from junction of two laminae Transverse process extends laterally from each side of vertebral arch Superior/inferior articular process (2 each)

o Protrude superiorly and inferiorlyo Smooth joint surfacesfacets covered with hyaline cartilageo Articular surfaces join to next vertebra

Regional vertebral characteristics TABLE OF COMPARISON

Movements: flexion/extension, lateral flexion, rotationCervical vertebrae

C1-C7lightest vertebrae C3-C7 features

o Oval body wider side to side than anteroposterior dimensiono Except in C7, spinous process is short, projects directly back + bifid

(splits at tip)

Large vertebral foramen generally triangular Transverse process contains transverse foramen vertebral arteries pass

to service brain

Spinous process of C7 not bifid much larger than other cervicalvertebrae

C1 + C2atlas + axis, more robust than tpical cervical vertebraeo No intervertebral disco Atlas C1no body, no spinous process holds up the worldo Axis C2 has a body (dens, odontoid peg missing body of atlas)

Thoracic vertebrae

12 all articulate with ribs Increase in size from first to last Body roughly heart shaped

o Bears two small facets demifacetsreceive head of ribs (T10-T12 only single facet)

Vertebral foramen circular Spinous process long, points sharply downwards T1-T10 transverse processes have facets transverse costal facets,

articulate with tubercles of the ribs


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Lumbar vertebrae

Receives most stress Large bodies, kidney shaped superiorly Pedicles/laminae shorter and thicker than those of other vertebrae Spinous processes short, flat, hatchet shapedrobust Triangular vertebral foramen

Sacrum

Posterior wall of the pelvis Formed by 5 fused vertebrae Articulates superiorly with L5 via superior articular processes, inferiorly

with coccyx

Articulates laterally with two hip bones via auricular surfacesformssacroiliac joints of pelvis

Wing-like alae laterally Vertebral canal continues inside sacrum as sacral canal Enlarged external opening sacral hiatuslaminae of fifth sacral

vertebrae fail to fuse medially

Coccyx

Tailbone 4-5 fused vertebrae Articulates superiorly with the sacrum

Bipedalism

Spinal curvature allows maintaining centre of mass, flexibility, balance

Increasing thickness/strength of descending vertebrae adaptation forweight bearing

Rib cage laterally orientated vs anteroposteriorly as in quadrupedsTHORACIC CAGE

Thoracic vertebrae Ribs Sternum

o Sternal angle Costal cartilagessecure ribs to sternum Bony thorax forms protective cage around vital organs of thoracic cavity,

supports shoulder girls + upper limbs + provides attachment points for

muscles


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Ribs

12 pairs All attach posteriorly to thoracic vertebrae curve down toward anterior

body surface

Superior 7 rib pairs attach directly to sternumindividual costalcartilages

o TRUE ribs Remaining 5 pairsfalse ribs

o Attach indirectly to sternum or entirely lack sternal attachmento 8-10 joining the costal cartilage immediately above ito 11-12 floating ribsno anterior attachments

Structureo Bulk of ribshafto Superior border is smootho Inferior border is sharp, thin and has a costal groove on inner faceo Head wedge-shaped articulates with vertebral bodies by twofacets

Body of same numbered thoracic vertebra Body of vertebra immediately superior

THE APPENDICULAR SKELETON

Bones of limbs + their girdleso Girdles connect axialappendicular skeletono Pectoral girdleo Pelvic girdle

Enables movement of manipulative lifestylePectoral (shoulder) girdle

Consists of clavicle anteriorly and scapula posteriorlyo Anteriorly, medial end of each clavicle joins the sternumo Posteriorly, distal ends of clavicles meet scapulae laterally

Scapulae attached to thorax + vertebral column only bymuscles

Attach upper limbs to axial skeleton Very light, allow the most mobility in the body because:

o Only clavicle attaches to axial skeleton scapula can move freelyo Shoulder joint socket shallow + poorly reinforced

Very unstableClavicles DISTINGUISH ORIENTATION

Cone shaped at medial sternal end, flat at acromial end Superior surface fairly smooth, inferior surface ridges/grooved by

ligaments + muscle action

Lateral 1/3 concave, medial 2/3 convex and rounded Not very strong likely to fracture

o Curved to ensure anterior fractures if posterior, subclavianartery would be damaged


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Scapulae

Thin, triangular flat bones 3 borders superior, medial and lateral 3 angles

o Lateral angle superior + lateralo Superior angle superior + medialo Inferior angle medial + lateral

Glenoid cavity articulates with the humeruso Shoulder joint

Anterior surface concaveo Coracoid process projects anteriorly from superior border

Anchors biceps brachii Bounded by suprascaular notch + glenoid cavity

Posterioro Prominent spine that ends laterallyo Acromion roughened triangular projection

Fossaeo Infraspinous + supraspinous inferior + superior to spineo Subscapular fossa entire anterior scapular surface

Upper limb

Humerus typical long bone

Articulates with scapula at the shoulder + with radius and ulna at elbow Head fits into glenoid cavity of scapula Greater + lesser tubercles sites of attachment of rotator cuff muscles

o Separated by intertubercular sulcus/bicipital groove guidestendons

Midway down the shaft deltoid tuberosityattaches the deltoidmuscle

Distal two condyleso Medial trochlea - articulates with ulnao Lateral ball-like capitulum articulates with radiuso Medial/lateral epicondyles muscle attachment sites

Fossaeo Anterior coronoid fossa superior to trochleao Posterior olecranon fossa

Forearm

Radius + ulnaUlna

Slightly longer than the radius mainly responsible for elbow joint withhumerus

Proximal end looks like adjustable end of monkey wrencho Two processes olecranon (elbow) + coronoid

Distal end shaft narrows and ends in a knoblike head

o Medialstyloid process


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Radius

Thin at proximal end wide at distal end Head shaped like head of a nail Styloid process

Wrist and hand Carpals wrist Metacarpals palm Phalanges fingers

Pelvic (hip) girdle

Attaches lower limbs to axial skeleton Transmits full weight of upper body to lower limbs Very secure deep sockets Formed by hip bones

o 3 separate bones: ilium, ischium, pubiso Deep socketacetabulum at point of fusion receives head of the

femur

Ilium

Forms superior region of coxal bone Superior edge iliac crests Anterior superior iliac spine Posterior superior iliac spine Greater sciatic notch

Iliac fossa

Ischium

Posteroinferior part of the hip bone Ischial tuberosity what we sit on

o Strongest parts of the hip bonesPubis

Anterior portion of hip bone Lies horizontally Obturator foramen closed by a fibrous membrane Pubic bones joined by fibrocartilage discpubic symphysis

o Inferiorinverted V-shaped pubic arch


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Pelvis structure + gender

Pubic arch Sacral curvature Pelvic brim

Female Generally tilted forward shallow, has a greater capacity Lighter, thinner, smoother bones Smaller acetabulum, farther apart Broader pubic angle (80-90 degrees), more rounded

Male

Generally tilted far less forward narrow and deep true pelvic cavity Heavier, thicker, more prominent markings on bones Larger acetabulum, closer together More acute pubic angle (50-60 degree)

Lower limb

Thigh femur

Largest, longest, strongest bone in the body Headneck Junction of shaft + necklateral greater trochanter and posteromedial

lesser trochanter

o Projections serve as sites of attachment for thigh/buttock muscles

Long vertical ridge along shaft

linea aspera Medial/lateral condylesarticulate with tibia

o Medial/lateral epicondyles Patellatriangular sesamoid bone secures anterior thigh muscles to

tibia

Tibia

Receives weight of body from femur + transmits it to the foot Tibial tuberosity patellar ligament attaches Distally, tibia is flatinferiorly, medial malleolus

o Medial bulge of ankleFibula

Stick-like Articulates proximally and distally with tibia

o Proximal end = heado Distal end lateral malleoluslateral ankle bulge


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Foot

Tarsus 7 tarsal bonesform posterior part of foot Talus articulates with tibia/fibula superiorly Calcaneus heel of the foot Metatarsals 5 Phalanges 14

JOINTS/ARTICULATIONS

Point of articulation of two or more bones Provide mobility Hold it together + protect Weakest parts of skeleton but CT makes it resist crushing or tearing

Classification of joints

By structure and function FUNCTION range of movement

o Synarthrosis: (together join) immoveableo Amphiarthrosis: (both sides) slightly moveableo Diarthrosis: freely moveable

STRUCTURALo Fibrous: no cavity, fibrous CTo Cartilaginous: no cavity, cartilageo Synovial: joint cavity + capsule

Fibrous joints

Bones joined by fibrous tissue

dense fibrous connective tissue

Most immoveable E.g. Sutures, syndesmoses

Synovial joines

Fluid-containing joint cavity at separation point Permits substantial freedom of movement

General structure of synovial joints

Articular cartilage hyaline cartilage covering articular surfaces of boneo Absorb compression + prevent crushing of bone ends

Joint (synovial) cavity potential space containing synovial fluid Articular capsule 2 layers

o External layer fibrous capsule DICTo Inner layer synovial membrane loose CT

Covers all internal joint surfaces that are not hyalinecartilage

Synovial fluido Reduces friction between cartilages

Reinforcing ligamentso Reinforces joints

Nerves and blood vessels


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Bursae/tendon sheaths

Bursae flattened fibrous sacs lined with synovial membrane containsthink film of synovial fluid

o Occur where ligaments, muscles, skin, tendons or bones rubtogether

Tendon sheaths elongated bursa that wraps completely around atendon subjected to friction

o Common where several tendons are crowded together withinnarrow canals

Movements allowed by synovial joints

Muscles origin attached to immoveable/less moveable bone Insertion attached to more moveable bone Range of movement

o Non-axial (slipping movements only)o Uniaxial one planeo Biaxial two planeo Multiaxial in or around all 3 planes

Types of movemento Glodingo Angular movementso Rotation

Gliding

Flat bone surface slips over another (back + forth, side to side)o Very limited movement

Intercarpal/intertarsal joins, flat articular processes of vertebraeAngular movements

Increase/decrease angle between two bones Flexion, extension, hyperextension, abduction, adduction, circumduction

Flexion

Bending movement, decreases angle of the joint brings articulatingbones closer together

o E.g. bending head forward on the chest, bending body trunk/kneefrom straight to angled position, lifting the arm anteriorly

Extension

Reverse of flexionoccurs at same joints Increases the angle between articulating bones typically straightens a

flexed neck, body trunk, elbow or knee

Excessive extensionhyperextension


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Abduction

Movement of a limb away from the midline/median plane along thefrontal plane

o E.g. raising arm/thigh laterallyAdduction

Opposite of abduction Movement of limb toward the body midline

Circumduction

Movement of a limb so that it describes a cone in space Hip/shoulder ball and socket joints

Rotation

Turning a bone around its own long axis Only movement allowed between two cervical vertebral/common at thehip Medial rotationdirected toward the midline Lateral rotationdirected away from the midline

Supination + pronation

Supination rotating forearm laterally palm faces anteriorly/superiorlyo Radius/ulna parallel

Pronation rotating forearm medially palm faces posteriorly/inferiorlyo Radius/ulna form X shape

Dorsiflexion + plantarflexion

Dorsiflexion lifting up the foot so that superior surfaceshin Plantarflexion pointing the toes (towards plants)

Types of synovial joints

Plane joints

Flat articular surfaces allow only short nonaxial gliding movements Gliding joints intercarpal/intertarsal, between vertebral articular

processes

o NO ROTATIONHinge joints

Cylindrical end of one bone fits into trough shape on another bone Movement along a single plane door hinge Permit flexion and extension

Pivot joints

Allows uniaxial rotation around long axis E.g. radius + ulna


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Injuries

Knees most susceptible to sports injuries because of high reliance onnonarticular factors for stability carry the bodys weight

Very vulnerable to horizontal blows e.g. football/ice hockey 3 Cs collateral ligaments, cruciate ligaments, cartilages (menisci) Most damaging lateral blows to extended knee tear TCL and medial

meniscus attached to it + anterior cruciate ligament

Q ANGLE

Small Q-angle genu varumo Bowlegged excess pressure placed on medial aspect of knee joint

destruction of the cartilage (arthrosis)

Large Q-angle genu valgumo Knocked knees overstretching of the TCL + excess pressure on

the lateral meniscus

Shoulder joint

Most freely moving joint but not very stable Ball and socket joint Humerus fits into glenoid cavity of scapular Articular capsule very loose and thin so great freedom of movement Few ligaments reinforcing shoulder joint primarily on anterior aspect

Structure

Incomplete girdle one attachment point to the axial skeleton(sternoclavicular joint) scapula attached via muscles to posterior wall ofthe thorax

o Allows greater range of movement Sternoclavicular joint synovial joint allowing fliding/axial rotation

Joint capsule

Loose fibrous sac extending from shallow glenoid cavityanatomicalneck of the humerus

Glenohumeral ligaments extend anteriorly from glenoid cavity anatomical neck loose and provide minimal strength to the joint

Weakest partinferior aspectDegree of movement

Role of upper limb does not involve weight-bearing/locomotionadapted for manipulation, balance and mobility

Shoulder joint allows flexion, extension, abduction, adduction,medial/lateral rotation + circumduction

Greater range of movement than any other joint within the body becauseof shallow glenoid fossa, loose capsule + ligaments, + mobility

Strength of joint relies on rotator cuff muscles secure and stabilize thejoint (attach scapula to humerus)


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Hip (coxal) joint

Ball and socket joint Good range of motion but not nearly as wide as shoulders range

o Movements limited by strong ligaments + deep socket

Joint formed by articulation of head of femus with acetabulum of hip bone Depth enhanced by circular rim of fibrocartilage Ligamentum teres aka ligament of the head of the femur

o Flat intracapsular band running from head of femur to lower lip ofthe acetabulum

o Contains an artery that helps supply the head of the femur


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Structure

Firmly attached to sacrum posteriorly completely encircles the pelvis toarticulate anteriorly at the pubic symphysis

o Pelvic girdle stable for transfer of weight to lower limbs via hipjoint

Sacroiliac joint partly synovial/partly fibrouso Thick fibrous ligaments restrict movement only slight gliding

movement allowed

Pubic symphysis is cartilaginous joint allowing very little or no movementJoint capsule

Fibrous capsule of hip joint very strong cylindrical sleeve enclosing deepjoint/most of femoral neck

Capsular ligaments iliofemoral, pubofemoral, ischiofemoral reinforcelongitudinal fibres of joint capsule

Degree of movement

All ball and socket movements possible but movement limited byacetabulum, muscles, ligaments and contact with coxal bones


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Osteoarthritis (degenerative joint disease)

Most common chronic arthritis wear and tear Softened, roughened, pitted, eroded articular cartilages Exposed bone tissue thickens stiff/less mobile joints

Rheumatoid arthritis

Chronic inflammatory disorder autoimmune disease Arises between 30-50 Early stages joint tenderness/stiffness common

Begins with inflammation of synovial membrane of affected joints Inflammatory cells migrate into joint cavity which destroy body tissues

o Synovial fluid accumulatesjoints swello Inflamed synovial membrane thickens erodes cartilageo Scar tissue connects bones ossifies/ joins immobilised


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SKELETAL MUSCULE TISSUE

MUSCULAR SYSTEM

Allows movement and posture attaches to bone Protection Heat production and storage Muscles made of CT and muscle fibres Regulation of blood/air flow (SM) All type of muscle excitable, contractile, extensile and elastic

SKELETAL MUSCLE

Striated Multinucleated Long Voluntarily controlled

STRUCTURE

Individual muscle fibres wrapped in endomysium Group of muscle fibres called a fascicle wrapped in perimysium Group of fascicle make up the muscles wrapped in epimysium Vascular has blood vessels running through it

MORE DETAIL


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Myofibril contains actin and myosin proteins Myofibril surrounded by sarcoplasmic reticulum (smooth ER) Muscle fibre plasma membrane called sarcolemma Sarcolemma has T-tubules which allow Ca to flow through and helps in

contraction

SMOOTH MUSCLE

FOUND: walls of tubes and hollow organs e.g. bladder, gut, bronchi Controls flow of blood, movement through gut, secretions/excretions to

be expelled

Single nucleus, not striated Gap junctions allow linked cells to act in unison Involuntarily controlled High capacity for stretch and elongation Not highly structured

CARDIAC MUSCLE

Main constituent of the heart Striated Involuntary Single nucleus Separated by intercalated discs

o Gap junctions allow functioning as functional syncytia (heartcontracts as a whole)

PacemakerNaming skeletal muscles

Location indicates bone/body region Shape some named for distinctive shapes e.g. orbicularis is round Relative size e.g. maximus, minimus, longus etc Direction of muscle fibres usually in relation to midline e.g. rectus =

straight, transversus = at right angles to midline etc

Number of origins e.g. biceps = 2 origins, triceps = 3 origins or heads Location of the attachments e.g. sternocleidomastoid

Action flexor, extensor, adductor

Arrangement of fascicles

Circular surround external body openingsclose by contracting sphincters

Convergent broad origin, narrow insertion fan shaped e.g. pec major Parallel straplike e.g. Sartorius Pennate short fascicles, attach obliquely feather


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Actions of muscles point of reference + movement

Agonist/prime mover: muscle mainly responsible for producingmovement e.g. biceps brachiielbow flexion

Antagonists: muscle whose action opposes the agonist e.g. triceps brachiibiceps brachii

Synergists: Helper to the agonist e.g. teres major + latissimus dorsi Fixators: synergistic muscles that specifically immobilize a bone e.g.

rhomboids fixing scapula

Rule of thumb

Muscles in the same compartment generally perform the same action Generally - ANTERIOR muscles from hip neck = flexors

o POSTERIOR muscles from hip downwards = flexorsFacial muscles

Obicularis oculi surrounds the orbitcloses the eye Zygomaticus major + minor pair extending diagonally from

cheekbonecorner of mouth, raises lateral corners of mouth upward

(smiling muscle)

Risorius inferior/lateral to zygomaticus draws corner of lip laterally(laughing muscle)synergist of zygomaticus

Obicularis oris forms the lips allows protrusion/closure of lips Buccinator deep to masseter principle muscle of cheek, compresses

cheek, holds food between teeth while chewing, draws corner of mouth

laterally

Masseter covers lateral aspect of mandibular ramus

prime mover ofjaw closer, elevates mandible

Temporalis closes jaw, elevates + retracts mandibleNeck muscles

Sternocleidomastoid two-headsflexes/laterally flexes/laterallyrotates the head

o Prime mover of head flexion Splenius extend from upper thoracic vertebrae to skull (mastoid

process)extend/hyperextend the head

Trunk muscles Erector spinae prime movers of extension of the vertebral column

o Spinalisalong spinous processeso Longissimusintermediate muscleo Iliocostalismost lateral muscle group

Quadratus lumborum lateral flexion of the vertebral column, extensionof lumbar spine, assists in respiration


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Abdominal wall musclesprime movers of flexion of vertebral column +

antagonists to erector spinae muscles

Rectus abdominis medially superficial External oblique laterally superficiallargest of the lateral muscles

o Pocketfibres run downwards and medially Internal oblique opposite direction to external obliquedeep to above

o Fibres run upward and medially Transversus abdominis deepest muscle of abdominal wall

o Fibres run horizontallyMuscles that stabilize the shoulder

Anterior

Pectoralis minor deep to pectoralis major, abducts scapula Serratus anterior holds scapula against chest wall

o Prime mover of scapula abduction punching musclePosterior

Trapezius 2x triangular, superficial adducts, stabilizes + elevates thescapula

Rhomboids deep to trapezius (rectangular shaped) medialacts toadduct the scapula

Rotator cuff muscles reinforce shoulder joint/hold head of humerus in glenoidfossa

Subscapularis medial rotation of humerus Infraspinatus lateral rotation of humerus Supraspinatus Teres minor lateral rotation of humerus

Upper limb muscles

Anterior flexion of the shoulder

Pectoralis major prime mover of arm flexion at shoulder, adduction,medial rotation of humerus

Coracobrachialis medial humerussynergist of pec major,adduction/flexion of humerus

Posterior extensors

Latissimus dorsi prime mover for arm extension at shoulder, adduction+ medial rotation of humerus antagonist to pec major

Teres major adducts/medially rotates humerus


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Abductors over the shoulder

Deltoid prime mover of arm abduction at shoulder Supraspinatus assists in abduction (intial 10 degrees)

Muscles that move the elbow

Anterior flexors

Biceps brachiiflexes forearm at elbow, supinates forearm Brachilis deep to biceps brachii, JUST LATERAL Brachioradialis from humerus to distal forearm

Posterior extensors

Triceps brachii 3 heads, prime mover of forearm extension at elbowMuscles that move the wrist

Anterior wrist/digit flexors + pronation of forearm

Palmaris longus inserts into palmar aponeurosis (easily palpated) Flexor carpi radialis just lateral to palmaris longus Flexor carpi ulnaris just medial to palmaris lungusinserts into

palmar aponeurosis

Surrounded by flexor retinaculumPosterior wrist/digit extensors

Extensor carpi radialis longus next to brachioradialis + originates inlateral epicondyle

Extensor carpi ulnarus Extensor digitorum prime mover of digit extension

Lower limb muscles move the leg at the hip

Iliopsoas psoas major + iliacus anterior

Psoas major mainly in abdomen, extends from lumbar vertebrae tolesser trochanter of femur

o Blends with iliacus FLEXES THE HIP

Gluteus maximus - posterior

Largest/most superficial muscle of gluteal region extends the thigh atthe hip, laterally rotates the thigh

Hamstrings posterior

Perform actions at the hip and knee jointo Hip extension (thigh at hip), raising trunk to standing position,

knee flexion

Biceps femoris Semitendinosus - medial Semimembranosus deep to semitendinosus


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Adductors

Medial compartment of thigh (magnus, longus, brevis) Adduct and flex thigh at the hip

Quadriceps femoris anterior compartment

Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius Extend the leg at the knee + rectus femoris flexes thigh at the hip

Satorius

Longest muscle in the body Flexion of the hip and knee, lateral rotation of the thigh (cross-legged)

Muscles that move the foot

Anterior dorsiflexion + toe extension

Tibialis anterior prime mover of dorsiflexion Extensor digitorum longus prime mover of toe extension

Posterior plantarflexion + toe flexion

Gastrocnemius prime mover of plantar flexion at the ankle + flexion ofknee

Soleus deep to gastrocnemius

Flexor digitorum longus deep muscle, flexes toes + plantar flexes foot atthe ankle

KNOW COMPARTMENTS

PHYSIOLOGY OF MUSCLE CONTRACTION

Microscopic anatomy of a skeletal muscle fibre


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Myofibrils

Rod-like 1-2um in diameter Contain contractile elements of skeletal muscle cells sarcomeres

Striations, sarcomeres, myofilaments Dark bands A bands, light bands I bands Each dark band has a lighter region in midsection H zone

o Bisected vertically by dark line M line I bands also have darker region Z disc/line Sarcomere smallest contractile unit of muscle fibre functional skeletal

muscle unit

o Region between two successive Z discsCross-sections

H-zone: thick filaments only I-band: thin filaments only M-line: thick filaments linked by accessory proteins Outer edge of A band thick/thin filaments overlap

Ultrastructure/molecular composition of myofilaments

Thick filaments primarily myosino Head-like structure attaches to actin to form cross-bridge

attachments

o Myosin head site for ATP binding

Thin filaments globular (G) and fibrous (F) actino G binding sites for myosin cross bridgeo Binding site usually covered by tropomyosino Troponin TnI inhibitory subunit that binds to actin, TnT binds to

tropomyosin, TnC binds to Ca2+ (from SR)

o Ca2+ binding to TnC exposes binding sitesSarcoplasmic reticulum/T-tubules

SR

Smooth ER Regulate intracellular levels of Ca2+ Stores Ca2+ and releases it on demand when muscle is contracted

T tubules

Sarcolemma protrudes deep into cell elongated tube formedT tubule


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Generation of AP across sarcolemma

AP arrives at axon terminal at neuromuscular junction ACh released ACh binds to receptors in sarcolemma chemically-gated Na+/K+

channels openpermeabilities change

AP propagates transmission of AP along T tubules changes shape ofproteins, stimulates SR calcium release into cytosol

Myosin heads bind to actin, contraction begins AP: 1-2ms, contraction 20-200ms

Muscle fibre contraction

Ca2+ levels rise ions bind to troponin sites, removes blocking action oftropomyosin (troponin changes shape)

Energised myosin head attaches to actin myofilament, forming a crossbridge

ADP + P released myosin head pivots/bends, changing to bent low-energy shape pulls on actin filament, sliding it toward M line ATP attaches to myosin, link between myosin + actin weakens myosin

head detaches

ATP hydrolyzed to ADP + P, myosin head returns to high-energy position Powered by ATP

Motor unit

Each muscle served by at least one motor nerve Motor unitmotor neuron + all muscle fibres it supplies

Fine control small motor unitso Muscle fibres in single motor unit spread throughout the muscle

weak contraction

Large, weight-bearing muscles (less precise movements) large motorunits

Muscle twitch

Response of a motor unit to single AP of its motor neuron 3 distinctphases

Latent period first few milliseconds following stimulationo Muscle tension beginning to increase but no response seen on

myogramo Ca2+ from SR

Period of contraction active cross bridgeso Sliding filamentso Onset to peak of tension development 10-100mso If tension > resistance, muscle shortens

Period of relaxation 10-100mso Initiated by re-entry of Ca2+ into SRo Muscle tension decreases to 0, tracing returns to baselineo Returns to initial length


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Muscle responses are smooth graded muscle responses via:

Changing the frequency of stimulation Changing the strength of stimulation

Changes in stimulus frequency

Increased muscular force by increased firing rate of motor neuronso Temporal summation

Successive contractions occur before muscle completely relaxes partially contracted already

Maximal tension fused/complete tetanusChanges in stimulus strength

Recruitmento Achieved by delivering shocks of increasing voltage to the muscle

Stimuli producing no observable contractions subthreshold stimulio First observable stimulus threshold stimuluso Beyond this point, muscle contracts more and more vigorously

Maximal stimulus strongest stimulus that produces increasedcontractile force all muscles motor units recruited

Isotonic/isometric contractions

Isotonic

Muscle length changes and moves the loado Once sufficient tension has developed to move the load, tension

remains relatively constant

Thin filaments sliding Concentric and eccentric Concentric muscle shortens e.g. picking up book, more familiar Eccentric muscle lengthens and generates force e.g. walking up stairs

(calf muscle) ~50% more forcefulmicrotears

Isometric

Tension builds but muscle neither shortens nor lengthens Occurs when muscle attempts to move load greater than tension muscle

can develop e.g. lifting piano singlehandedly

Occur when acting to maintain upright posture/hold joints in stationarypositions

Cross bridges generating force but not moving thin filamentsMuscle metabolism

Muscle stores have very little reserves of ATP Direct phosphorylation of ADP by creatine phosphate Anaerobic glycolysis glucose lactic acid Aerobic respiration


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Direct phosphorylation of ADP by creatine phosphate

Creatine phosphate high-energy molecule stored in muscles Muscles store 2-3 times as much CP as ATP Very efficient provide for maximum muscle power for 14-16 seconds

Anaerobic pathway glycolysis + lactic acid formation

As stored ATP/CP are exhausted, more ATP generated by breakdown ofglucose obtained from blood/glycogen stored in the muscle

Initial stage of glucose breakdown glycolysis Glucose2 pyruvate + 2 ATP per molecule Pyruvic acidlactic acid, enough energy for ~60s of exercise

Aerobic pathway

95% of ATP source

Occurs in the mitochondria Indirectly 32ATP per glucose but slow and requires oxygen

Short duration exercise

6 seconds ATP stored in muscles used first 10 seconds ATP from CP and ADP 30-40seconds glycogen stored in muscles broken down to glucose,

oxidized to generate ATP

Prolonged-duration exercise

Aerobic glycolysisMuscle fatigue

Physiological inability to contract even if muscle is still receiving stimuli APs generated K+ lost from muscle cells ATPase pump inefficient so

K+ accumulates in fluids of T tubules

o MP disturbed, Ca2+ not released from SR Potential causes: ATP deficit, accumulation of ADP, lactic acid, ions ACh release impaired, CP reduced, Ca2+ stores reduced, glycogen reduce,

insufficient O2

Oxygen deficit

Amount of oxygen required to restore resting state Oxygen reserves must be replenished Accumulated lactic acidpyruvic acid Glycogen stores replaced ATP/CP reserves resynthesized Liver lactic acid in blood glucose/glycogen Heat major waste product only about 40% of energy released is useful


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Force of muscle contraction affected by:

Number of muscle fibres stimulated Relative size of the fibres Frequency of stimulation Degree of muscle stretch

Number of muscle fibres stimulated

Increased motor units recruited, greater the muscle forceSize of the muscle fibres

Bulkier muscles (greater cross-sectional area), more tension it candevelop greater strength

Frequency of stimulation

Rapid stimulation contractions summed Temporal summation

Degree of muscle stretch

Optimal operating length is length of maximal force generation Ideal length-tension relationship muscle slightly stretched, thin+thick

filaments overlap optimally

Between 80-120% of optimal resting lengthMuscle fibre type

Speed of contraction speed of shortening slow/fast fibreso

Difference in speed refects how fast myosin ATPases split ATP +electrical activity of motor neurons

o Depends how quickly Ca2+ moved from cytosol SR Major pathways for forming ATP

o Mostly reliant on oxygen-using aerobic pathways oxidative fibreso Mostly reliant on anaerobic glycolysis glycolytic fibres

Skeletal muscle cells classified

Slow oxidative (SO) fibres Fast oxidative (FO) fibres Fast glycolytic (FG) fibres

Slow oxidative fibres endurance exercise

Contract slowlyo Because myosin ATPases are slow

Depends on oxygen/aerobic pathways Fatigue resistant/has high endurance typical of aerobic fibres Thin large amount of cytoplasm impedes diffusion of O2/nutrients from

blood

o BECAUSE SLOW Little power because thin so limited number of myofibrils Many mitochondria because aerobic Red abundant supply of myoglobin storing O2 reserves


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Fast glycolytic fibres short intense/powerful movements

Contracts rapidlyo Myosin ATPases fast

Depends on glycogen reserves rather than on blood-delivered nutrients Tires quickly glycogen reserves short-lived, lactic acid accumulates

quickly

Large diameter Few mitochondria, little myoglobin, low capillary dense so white

Fast oxidative fibres

Contract quickly but oxygen dependent, rich supply ofmyoglobin/capillaries

Effect of exercise on muscles

Aerobic

DOES NOT PROMOTE SKELETAL MUSCLE HYPERTROPHY Increased number of capillaries surrounding muscle fibres Increased number of mitochondria within muscle fibres More myoglobin Most dramatic in slow oxidative fibres depending primarily on aerobic

pathways

More efficient muscle metabolism greater endurance, strength,resistance to fatigue

Resistance

Increased individual muscle fibres esp. FG fibresSmooth muscle

Spindle-shaped, uninucleate Most organized into sheets

o GI tract, blood vessels, respiratory/reproductive tract In most cases, two sheets present fibres at right angles to each other

o Longitudinal layer fibres run parallel to long axis of organo Circular fibres run around the circumference

Smooth muscle contraction

No T-tubules SR less developed Actin + myosin interact by sliding filament mechanism Final trigger for contraction rise in intracellular Ca2+ ion level Energised by ATP Ca2+ binds to calmodulin which interacts with myosin kinase and

activates myosin

Electrically coupled by gap junctions Takes 30x longer to contract and relax than skeletal muscle but can

maintain same contractile tension for prolonged periods at less than 1%of the energy cost


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APS1 Notes

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