Snell Abdomen

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Abdomen22C H A P T E R

ANTERIOR ABDOMINAL WALL

Skin NERVE SUPPLYThe cutaneous nerve supply to the anterior abdominal wallis derived from the anterior rami of the lower six thoracic

and the first lumbar nerves (Figs. 2-1 and 2-2). The thoracicnerves are the lower five intercostal and the subcostalnerves; the first lumbar nerve is represented by the iliohy-

pogastric a nd the ilioinguinal nerves.The d ermatom e o f T7 is loca ted in the ep igastrium over

the xiphoid process. The dermatome of T10 includes theumbilicus, and that of L1 lies just above the inguinal liga-ment and the symphysis pubis. The dermatomes and dis-tribution of cutane ous nerves are shown in Figures 2-3 and2-4.

BLOOD SUPPLY

ArteriesThe skin nea r the midline is supp lied b y branche s of the su-

pe rior an d the inferio r ep igastric arte ries. The skin of theflanks is supplied by branch es of the intercostal, the lumbar,and the deep circumflex iliac arteries (Fig. 2-1).

Veins

The venous d rainage pa sses ab ove into the axillary vein viathe lateral thoracic vein and below into the femoral veinvia the superficial epigastric and the great saphenousveins.

LYMPH DRAINAGE

The c utane ous lymph vessels above the level of the umb ili-

cus drain upward into the anterior axillary lymph nodes.The vessels below this level drain downward into thesuperficial inguinal nodes.

Superficial FasciaThe superficial fascia is divided into the superficial fattylayer (fascia of Camper) and the deep membranouslaye r (Scarpa’s fascia).

The fatty layer is continuous with the superficial fasciaover the rest of the body. The membranous layer fades outlaterally and abo ve. Inferiorly, the m emb ranous layer passesover the inguinal ligamen t to fuse with the deep fascia of the

CAVAL –C AVAL ANASTOMOSIS ANDP ARAUMBILICAL VEINS

Note the important indirec t conne ction be tween the

superior and inferior venae cavae. This may permitthe reversal of blood flow in patients with an ob-structed vena cava caused by a large mediastinal or abdominal tumor. Note also the presence of smallparaumbilical veins that connect the systemic skinveins in the region of the umbilicus along the liga-men tum teres to the portal vein. This may provide animportant portal–systemic anastomosis in patientswith obstruction of the portal vein, as in cirrhosis of the liver.

CLINICAL NOTES


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xiphoid process

iliohypogastric nerve

ilioinguinal nerve

inferior epigastric artery position of deep inguinal ring

deep circumflex iliac artery

lumbar arteries

intercostal arteries

lateral margin of rectus sheath

superior epigastric artery

T7

T8

T9

T10T11

T12

L1

Figure 2-1 Seg me ntal inne rvation (left) and arterial sup ply (right) to the abd om inal wa ll.

sacrospinalis

posterior cutaneous nerves

posterior ramus

quadratus lumborum

external oblique

anterior cutaneous nerves

T7-12

T11

L1 psoas

internal obliqueL1

transversus

rectus muscles

Figure 2-2 Cross s ection of the abdo me n sho wing the course s of the lower thoracic and the first lum bar ne rves.

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CHAPTER2 Abdomen 37

transverse cutaneous nerve of neck

supraclavicular nervesanterior cutaneous branch of secondintercostal nerve

upper lateral cutaneous nerve of arm

medial cutaneous nerve of arm

lower lateral cutaneous nerve of armmedial cutaneous nerve of forearm

lateral cutaneous nerve of forearm

lateral cutaneous branch of subcostal nerve

femoral branch of genitofemoralnerve

median nerveulnar nerve

ilioinguinal nervelateral cutaneous nerve of thigh

obturator nervemedial cutaneous nerve of thigh

intermediate cutaneous nerve of thigh

infrapatellar branch of saphenous nerve

lateral sural cutaneous nerve

saphenous nerve

superficial peroneal nerve

deep peroneal nerve

C2

C3

C4

C5

T2

C6

T1

C8

C7L1

S3

S4

L2

L3

L4

L5

S1

T3

T4

T5T6T7T8T9

T10T11

T12

Figure 2-3 Dermatom es a nd dis t r ibut ion of cutaneou s ne rves on the an ter ior aspe ct of the body.


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38 CHAPTER2 Abdomen

greater occipital nervethird cervical nerve

great auricular nerve

fourth cervical nervelesser occipital nerve

supraclavicular nerve

first thoracic nerve

posterior cutaneous nerve of arm

medial cutaneous nerve of arm

posterior cutaneous nerve of forearm

medial cutaneous nerve of forearm

lateral cutaneous nerve of forearmlateral cutaneous branch of T12

posterior cutaneous branches of L1, 2, and 3 radial nerve

ulnar nerve

posterior cutaneous branches of S1, 2, and 3

branches of posterior cutaneousnerve of thigh

posterior cutaneous nerve of thigh

obturator nerve

lateral cutaneous nerveof calf

sural nerve

saphenous nerve

lateral plantar nerve

medial plantar nerve

C2

C3

C5C6

C5

T2

T1

C7C6

C8

L1S5

S4

S3L2

S2

L3

L5

L4

S1

L5

T2

T3

T4

T5

T6T7T8T9

T10T11T12

C4

Figure 2-4 Dermatom es an d distribution of cutaneo us ne rves on the poste rior aspe ct of the bod y.


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CHAPTER2 Abdomen 39

thigh (fascia lata) approximately one fingerbreadth belowthe inguinal ligament. In the midline, it is not attache d to the

pubis bu t instead forms a tubular shea th for the pe nis (cli-toris). In the perineum, it is attached on each side to themargins of the pubic arch and is known as Colles’ fascia.Posteriorly, it fuses with the perineal b ody an d the posterior margin of the perineal membrane.

oblique fuses with the anterior lamina, and the transversusaponeu rosis fuses with the posterior lamina. At the level of the an terior superior iliac spines, all three ap oneuroses passanteriorly to the rec tus muscle, leaving the shea th de ficient

po ste riorly below this leve l. The lower, crescen t-shap ededge o f the p osterior wall of the sheath is called the arcuateline. All three aponeuroses fuse with each other and withtheir fellows of the op posite side in the m idline between theright and the left recti muscles to form a fibrous band calledthe linea alba, which extends from the xiphoid processabove to the pub ic symph ysis below.

The p osterior wall of the shea th, however, has no attach-ment to the muscle. The transverse tendinous intersec-tions, which divide the rectus abdominis muscle into seg-ments, are usually three in number: One at the level of thexiphoid process, one at the level of the umbilicus, and one

be tween these two.

Deep FasciaIn the anterior abd omina l wall, the deep fascia is a thin layer of areolar tissue covering the muscles.

Muscles of the Anterior Abdominal WallThe muscles of the a nterior abdominal wall consist mainly of

three broad, thin sheets that are aponeu rotic in front. Fromexterior to inferior, these sheets are the external oblique,the internal oblique, and the transversus (Fig. 2-5). In ad-dition, on either side of the midline anteriorly, there is awide, vertical mu scle called the rectus abdominis (Fig. 2-6). As the ap oneu roses of the three shee ts pass forward, theyenc lose the rectus abdominis to form the rectus sheath.

In the lower part of the rectus sheath, there may be asmall muscle called the pyramidalis.

The cremaster muscle is derived from the lower fibersof the internal oblique; it passes inferiorly as a covering of the spermatic c ord and enters the scrotum.

The muscles of the anterior abdo minal wall are shown inTable 2-1.

RECTUS SHEATH

The rectus sheath (Fig. 2-7) is a long fibrous sheath that en-closes the rectus abdominis muscle and pyramida lis muscle(if present) and contains the anterior rami of the lower sixthoracic n erves and the superior and inferior epigastric ves-sels and lymph vessels. It is formed by the aponeuroses of the three lateral abdominal muscles. The internal obliqueaponeurosis splits at the lateral edge of the rectus abdomi-nis to form two laminae; one passes anteriorly and one pos-teriorly to the rectus. The aponeurosis of the external

LINEA SEMILUNARIS

The linea semilunaris is the lateral edge of the rectus abdo -minis muscle. It crosses the costal margin at the tip of theninth costal cartilage.

CONJ OINT TENDON

The internal oblique muscle has a lower, free border thatarches over the spermatic cord ( or the round ligamen t of theuterus) an d then descen ds behind and attaches to the pubiccrest and the pectineal line. Near their insertion, the lowesttendinous fibers are joined by similar fibers from thetransversus abd ominis to form the conjoint tendon, whichstrengthens the medial half of the posterior wall of theinguinal canal.

INGUINAL LIGAMENT

The inguinal ligamen t (Fig. 2-5) conn ects the anterior supe-rior iliac spine with the pubic tubercle. This ligament isformed by the lower border of the aponeu rosis of the exter-nal ob lique muscle, which is folded bac k on itself. From themedial end of the ligament, the lacunar ligament extends

ba ckwa rd a nd upward to the pec tineal line on the superior ramus of the pubis, where it becomes continuous withthe pectineal ligament (a thickening of the periosteum).The lower border of the inguinal ligamen t is attached to thedee p fascia of the thigh (the fascia lata ) .

SUPERFICIAL FASCIA AND THEEXTRAVASATION OF URINE

The membranous layer of superficial fascia has be-neath it a potential closed space that does not ope ninto the thigh but is continuous with the superficial

pe rineal pouch via the penis and scro tum . Rup ture of the penile urethra may be followed by extravasationof urine into the scrotum, perineum, and penis andthen up into the lower part of the anterior abdominalwall deep to the membranous layer of fascia. Theurine is excluded from the thigh because of the at-tachm ent of the fascia to the dee p fascia of the thigh.

CLINICAL NOTES

SURGERY AND TENDINOUS INTERSECTIONSOF THE ABDOMINIS MUSCLE

Note tha t the anterior wall of the rec tus sheath is firmlyattached to the tendinous intersections of the rectusabdominis muscle. The posterior wall of the sheath,however, has no attachment to the muscle.

CLINICAL NOTES


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40 CHAPTER2 Abdomen

external oblique muscle linternal oblique muscle

iliac crest

inguinal ligament

lumbar fascia

superficialinguinal ring

pubic tubercle

transversus muscle

lumbar fascia

inguinal ligament

Figure 2-5 External oblique , internal oblique , and trans versus mu scles of the anterior abd om inal wall.


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CHAPTER2 Abdomen 41

xiphoid process

tendinous intersections

external obliquemuscle

linea semilunaris

rectus muscle

inguinal ligament

pubic tubercle

superficial inguinal ring

spermatic cord

pyramidalis

anterior superior iliac spine

arcuate line

internal oblique muscle

linea alba

Figure 2-6 Anterior view of the rectus abdom inis mu scle and the rectus shea th. Left: The anterior wall of sheath ha s bee n partly rem oved revea ling the rectus m uscle with its tendinous intersec-tions. Right: The posterior wall of the rectus she ath. Note the edg e of the arcuate line a t the levelof the a nterior supe rior i liac spine.

FASCIA TRANSVERSALIS

The fascia transversalis is a thin layer of fascia that lines thetransversus muscle a nd is continuous with a similar layer lin-ing the diaphragm and the iliacus muscle. The femoralsheath of the femoral vessels is formed by the fasciatransversalis an d the fascia iliaca.

INGUINAL CANALThe inguinal cana l (Fig. 2-8) is an oblique passage throughthe lower pa rt of the anterior abdom inal wall. In males, it al-lows structures to pass to and from the testis to the ab-domen. In females, it allows the round ligament of theuterus to pass from the u terus to the labium m ajus.

The canal is approximately 1.5 in. (4 cm) in lengthamong adults and extends from the deep inguinal ringdownward and medially to the superficial inguinal ring.It lies parallel to and immediately above the inguinalligament.

The deep inguinal ring is an oval opening in thefascia transversalis and lies approximately 0.5 in. (1.3 cm)

above the inguinal ligament. The margins of this ring giveattachment to the internal spe rmatic fascia.

The superficial inguinal ring is a triangular-shaped de-fect in the aponeurosis of the external oblique muscle andlies immediately above and medial to the pubic tubercle.The margins of this ring give attachment to the externalspermatic fascia.

Walls

• Anterior w all: External ob lique aponeu rosis, reinforcedlaterally by origin of the internal ob lique from the inguinalligament (Fig. 2-8).

• Posterior wall: Conjoint tend on med ially, fascia transver-salis laterally (Fig. 2-8).

• Roof or superior wall: Arching fibers of the internaloblique and transversus muscles (Fig. 2-8).

• Floor or inferior wall: Inguinal and lacuna r ligaments.

Function of the Inguinal Canal

In males, the inguinal cana l allows structures to pass to andfrom the testis to the abdomen. (Normal spermatogenesis


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42 CHAPTER2 Abdomen

Table 2-1 Muscles of the Anterior Abdominal Wall

Name of Muscle Origin Insertion Nerve Supply Action

External oblique Lower right ribs Xiphoid process, linea Lower six thoracic Compresses abdominalalb a, pub ic cre st, nerves, iliohypoga stric con te nts; a ssists in

pu bic tub erc le, iliac an d ilioin guinal flexing and rota tion

crest nerves (L1) of trunk; pulls downribs in forcedexpiration

Internal oblique Lumbar fascia, iliac Lower three ribs and Lower six thoracic Compresses abdominalc re st, la te ra l two third s c osta l c artila ge s, n erve s, ilio hyp oga stric c on te nts; a ssists inof inguinal ligament xiphoid process, and ilioinguinal flexing and rotation

linea alba, symphysis nerves (L1) of trunk; pulls down pu bis; forms c on joint ribs in force dtendon with expirationtransversus

Transversus Lower six costal Xiphoid process, linea Lower six thoracic Compresses abdominalcartilages, lumbar alba, symphysis nerves, iliohypogastric contentsfascia, iliac crest, pubis; forms conjoint and ilioinguinallateral third of tendon with internal nerves (L1)inguinal ligament oblique

Rec tus a bd ominis Symphysis pub is and Fifth, sixth, a nd se venth Lowe r six thorac ic Compresses ab domina l pubic cre st co stal cartilages and ne rves co nte nts a nd flexes

xiphoid process vertebral column;accessory muscle of expiration

Pyramidalis Anterior surface of Linea alba Twelfth thoracic nerve Tenses the linea alba(often absent) pubis

Cremaster Lower margin of internal Pubic crest Genital branch of genito- Retracts testisoblique muscle femoral nerve (L1, 2)

skin

rectus muscle

A

xiphoid process7 6 5 intercostal muscles

aponeurosis of external oblique

pectoralis major musclesuperficial fascia

rectus muscle

linea alba

B

extraperitoneal fat peritoneum

fascia transversalis

transversusinternal obliqueexternal oblique

C

external obliqueinternal obliquetransversus

fascia transversalis

Figure 2-7 Transverse sect ions o f the rectus she ath . A: Above the costa l margin . B: Between thecostal marg in an d the level of the a nterior superior il iac spine. C: Below the level of the anterior supe rior i liac spine a nd a bove the pubis.


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CHAPTER2 Abdomen 43

A

external oblique

femoral sheath

femoral arterylymphatic vessels

ilioinguinal nerve pubic tubercle

spermatic cordsymphysis pubis

superficial inguinal ring

linea alba

Binternal oblique

ilioinguinal nervecremaster muscle

femoral vein

pectineal line pubic crest

transversus muscleinferior epigas tric

arteryC

deep inguinal ring

fascia transversalis conjoint tendon

D

inferior epigastric artery

pubic tubercle

spermatic cord


Figure 2-8 The inguinal canal. Note the arrang em ent o f (A) the externa l oblique m uscle, (B) the in-ternal oblique mu scle, (C) the trans versus mu scle, and (D) the fascia transversalis. The an terior wall is forme d by the external and the internal oblique mu scles, and the poste rior wa ll is forme d

by t he fa scia tr ansve rs a lis a nd th e co n jo in te ndon . Th e deep ingu ina l rin g lie s la te ra l to th e infe rio r epigastric artery.


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44 CHAPTER2 Abdomen

occurs only if the testis leaves the abd omina l cavity and e n-ters a cooler environment in the scrotum.) In females, thesmaller canal allows the rou nd ligament of the uterus to pa ssfrom the u terus to the labium majus. In bo th sexes, the c ana lalso transmits the ilioinguinal nerve.

Mechanics of the Inguinal CanalThe inguinal canal is a site of potential weakness in bothsexes. On co ughing and straining (as in m icturition, defeca-tion, and parturition), the arching lowest fibers of the inter-nal oblique and transversus abdominis muscles contractand flatten the a rch. In turn, this lowers the roof of the cana ltoward the floor and virtually closes the can al.

• Rema ins of the processus vaginalis.• The c remasteric artery.• The artery of the vas deferens.• The genital branch of the genitofemo ral nerve, which sup-

plies the crema ster musc le.

Coverings of the Spermatic CordThere are three concen tric layers of fascia derived from thelayers of the anterior abdom inal wall:

• External spermatic fascia derived from the externaloblique muscle and attached to the margins of thesuperficial inguinal ring.

• Cremasteric fascia derived from the internal obliquemuscle.

• Internal spermatic fascia derived from the fasciatransversalis and attached to the margins of the deepinguinal ring.

PROCESSUS VAGINALIS

The processus vaginalis is a p eritoneal d iverticulum formedin the fetus that passes through the lower part of the an terior abd omina l wall to form the inguinal cana l. The tunica vagi-nalis is the lower, expanded part of the processus vaginalis.

Norma lly, the cavity of the tunica vagina lis be come s shut off from the upper part of the processus and the peritoneal cav-ity just before birth. The tunica vaginalis is thus a closed sacinvaginated from behind by the testis.

Spermatic Cord

The spermatic cord is a collection of structures that passthrough the inguinal canal to and from the testis. Thesestructures include the following:

• The vas deferens.• The testicular artery.• Testicular veins (pampiniform plexus).• Testicular lymph vessels.• Autonomic nerves.

INGUINAL H ERNIA

An inguinal hernia occurs above the inguinal liga-

ment, whereas a femoral hernia occurs below the in-guinal ligament. Inguinal hernias are of two types:indirect and direct.

Indirect Inguina l Hern ia• The he rnial sac is the rema ins of the processus

vaginalis.• An indirect inguinal hernia is more common than a

direct inguinal hernia.• It is much more com mon in males than in females.• It is more common o n the right side.• It is most common in children and young adults.• The he rnial sac enters the inguinal canal through

the dee p inguinal ring and lateral to the inferior epi-gastric vessels. The neck of the sac is narrow.

• The h ernial sac m ay extend through the superficialinguinal ring above and medial to the pubic tuber-cle (femoral hernia below and lateral to the pubictubercle).

• The he rnial sac ma y extend down into the scrotumor labium ma jus.

Direct Inguin a l Hernia• It is common amon g elderly men with weak ab-

dominal muscles but is rare among women.• The he rnial sac bulges forward through the posterior

wall of the inguinal canal medial to the inferior epi-gastric vessels.

• The ne ck of the he rnial sac is wide.

CLINICAL NOTES

CLINICAL ANATOMY OF THEP ROCESSUS VAGINALIS

The processus vaginalis is a peritoneal diverticulum,formed in the fetus, that passes through the layer of the anterior abdominal wall to form the inguinalcanal. The tun ica vaginalis is the lower expanded p artof the processus vaginalis. Normally, just before birth,the cavity of the tunica vaginalis becomes shut off from the upper part of the processus and the peri-tonea l cavity. The tunica vaginalis is thus a closed sac,invaginated from behind by the testis. The followinganoma lies may occu r:

• Preformed sac of indirect inguinal hernia: The processus m ay persist partia lly or in its en tirety as a

hernial sac.• Congenital hydrocele: The processus vaginalis be -comes n arrowed but not o bliterated and remains incomm unication with the abdo minal cavity. Peri-tonea l fluid accumu lates in it, forming a hydrocele.

• Encysted hydrocele of the cord: The upp er andlower ends of the processus become obliterated,leaving a small intermediate encysted area . This pre-sents as a small fluctuant swelling in the inguinal re-gion, often within the inguinal cana l, that mo ves me-dially on gentle downward pu lling of the testis andthe covering of tunica vaginalis.

CLINICAL NOTES


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GUBERNACULUM TESTIS

The gubernac ulum testis is a musculoligamen tous cord thatconnec ts the fetal testis with the floor of the developing scro-tum. It plays an important role in the descent of the testis,and it is homologous to the female round ligament of the

ovary and the round ligamen t of the uterus.

SCROTUM

The scrotum is an outpouching of the lower part of theanterior abdominal wall. It contains the testes, theepididymides, and the lower en ds of the sperma tic cords.

The wall of the scrotum has the following layers:

• Skin.• Superficial fascia, in which dartos muscle (smoo th

muscle) replaces the fatty layer.• External spermatic fascia from the external oblique

muscle.• Cremasteric fascia from the internal oblique mu scle; the

cremasteric muscle is supplied by the genital branch of the genitofemoral nerve.

• Internal sperma tic fascia from the fascia transversalis.• Tunica vaginalis (a closed sac that covers the anterior, me-

dial, and lateral surface s of each testis).

TESTES

The testes are pa ired, o void o rgans responsible for the pro-duction of spermatozoa and testosterone. Normal sper-matogene sis occ urs only at a temperature lower than tha t of the abdominal cavity, hence the descent of the testes intothe scrotum. The tunica albuginea is the outer, fibrouscapsule of the testis.

EPIDIDYMIDES

The epididymis on e ach side lies posterior to the testis andhas a head, a body, and a tail. It is a coiled tube app roxi-mately 20 ft. (6 m) in length. The vas de ferens emerges fromthe tail.

Blood Supply of the Tes tis and Epididymis

The testicular artery is a b ranch of the abd omina l aorta. Thetesticular vein emerges from the testis and the epididymis asa venous network (the pampiniform plexus ), which be-comes reduced to a single vein as it ascends through the in-

guinal canal. The right testicular vein drains into the inferior vena cava, and the left vein joins the left renal vein.

Lymph Drainage of the Tes tis and Epididymis

Para-aortic lymph nod es on the side of the ao rta at the levelof the first lumbar vertebra.

CHAPTER2 Abdomen 45

testicular vein drains into the low-pressure inferior vena cava, whereas the left vein d rains into the left re-nal vein, in which the venus pressure is higher. Veryrarely, a malignant tumor of the left kidney with inva-sion of the left rena l vein may block the exit of the tes-

ticular vein.

Nerves o f the Anterior Abdominal WallThe nerves of the anterior abdominal wall are the anterior rami of the lower six thoracic and the first lumbar nerves(Fig. 2-2). These nerves run downward and forward be-tween the internal oblique and the transversus muscles.They supply the skin, the muscles, and the parietal peri-toneum of the anterior abdominal wall. The lower six tho-racic nerves pierce the posterior wall of the rectus sheath.The first lumbar nerve is represented by the iliohypogas-tric and the ilioinguinal nerves, which do not enter the

rectus sheath. Instead, the iliohypogastric ne rve p ierces theexternal oblique apone urosis abo ve the superficial inguinalring, and the ilioinguinal ne rve pa sses through the inguinalcanal to emerge through the ring.

Blood Supply of the AnteriorAbdominal Wall

ARTERIESThe superior epigastric artery arises from the internal tho-racic artery and enters the rectus sheath. It desce nds be hindthe rectus muscle, supplies the uppe r central part of the an -terior abdominal wall, and anastomoses with the inferior epigastric artery.

The inferior epigastric artery arises from the externaliliac a rtery abo ve the inguinal ligame nt. It runs me dial to thedee p inguinal ring and enters the rectus sheath, ascend s be-hind the rectus muscle, and supplies the lower central partof the anterior abdominal wall. It anastomoses with thesuperior epigastric artery.

The deep circumflex iliac artery is a branch of the ex-ternal iliac artery. It runs upward and laterally toward the an -terior superior iliac spine, and it supplies the lower lateral

pa rt of the ab do minal wall.The lower two posterior intercostal arteries from

the descending thoracic aorta and the four lumbar arter-

VARICOCELE

In varicocele, there is an elongation and dilation of the veins of the pampiniform plexus. It is a commondisorder found in adolescents and young adults. Thegreat majority occur on the left side, beca use the right

CLINICAL NOTES

TESTICULAR TUMOR

A testicular tumor is usually a hard, irregular, non-tender mass. Note that if the tumor is malignant it willmetastasize to the para-aortic lymph nod es at the levelof the first lumbar vertebra.

CLINICAL NOTES


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46 CHAPTER2 Abdomen

ie s from the abdominal aorta supply the lateral part of theanterior abdominal wall. The superficial epigastricartery, the superficial circumflex iliac artery, and thesuperficial external pudendal artery bra nches of thefemoral artery also supply the lower part of the anterior abdominal wall.

VEINS

The superior and inferior epigastric ve ins and the deepcircumflex iliac ve ins follow the arteries and d rain into theinternal thoracic and the externa l iliac veins. The posteriorintercostal veins drain into the azygos veins, and the lum-bar veins drain into the inferior vena cava. The superficialepigastric, the superficial circumflex iliac, and thesuperficial external pudendal veins drain into the greatsaphenous vein and, from the re, into the femoral vein. Thethoracoepigastric vein is the name given to the anasto-moses be tween the lateral thoracic vein and the sup erficialepigastric vein, which is a tributary of the great saphe nousvein. This vein provides an alternative p ath for the venous

blood sho uld the sup erio r or inferior ven a ca va bec om eobstructed, a s previously noted.

Lymph Drainage of the AnteriorAbdominal WallThe c utaneous lymph vessels abo ve the level of the um bili-cus drain upward into the anterior axillary lymph nodes.Cutane ous lymph vessels below this level drain downwardinto the sup erficial inguinal nodes. The deep lymph vesselsfollow the arteries and drain into the internal thoracic, theexternal iliac, the posterior mediastinal, and the para-aortic(lumbar) nodes.

PERITONEUM

The peritoneum is the serous membrane that lines the ab-dom inal and the pe lvic cavities and tha t clothes the viscera(Fig. 2-9). The peritoneum can be regarded as a balloonagainst which organs are pressed from the outside. Theparietal layer lines the walls of the abdominal and the

pe lvic cavities, an d the visceral layer covers the organs.The potential space between the parietal and the viscerallayers is called the peritoneal cavity. In males, this is aclosed cavity, but in females, there is communication with

the exterior through the uterine tubes, the uterus, and thevagina.

The peritone al cavity is divided in to two parts: the grea ter sac and the lesser sac (Fig. 2-9). The greater sac is the m aincompa rtment an d extends from the diaphragm down intothe pelvis. The lesser sac is smaller and lies behind thestomach . The greater and the lesser sacs are in free co mmu -nication with one another through the epiploic foramen.The peritoneum secretes a small amount of serous fluid thatlubricates the peritone al surface s and facilitates free move-ment between the viscera.

Peritone al Ligaments, Omenta,and MesenteriesThe peritoneal ligaments, omenta, and mesenteries permit

blood , lymph vessels, and ne rves to reach the visce ra.

PERITONEAL LIGAMENTS

Peritoneal ligaments are two-layered folds of peritoneumthat connect solid viscera with the abdominal walls. Theliver, for examp le, is conn ected to the diaphragm by the fal-ciform ligament, the coronary ligament, and the rightand the left triangular ligaments (Fig. 2-10).

OMENTA

Omenta are two-layered folds of peritoneum that connectthe stomach with another viscus. The greater omentumconnects the greater curvature of the stomach with thetransverse colon (Fig. 2-9). It hangs down like an apron infront of the co ils of the small intestine an d is folded back onitself. The lesser omen tum suspends the lesser curvature of the stomach to the fissure for the ligamentum veno sum andthe porta hepatis of the liver (Figs. 2-9 and 2-10). The gas-trosplenic omentum (ligament) co nnects the stomach tothe hilus of the spleen .

MESENTERIES

Mesenteries are two-layered folds of peritoneum connect-ing parts of the intestines with the posterior abdominalwall (e.g. , the mesentery of the small intestine,the transverse mesocolon, the sigmoid mesocolon )(Fig. 2-9).

Lesser SacThe lesser sac lies behind the stomach and the lesser omentum (Fig. 2-9). It extends upward as far as the di-aphragm and downward between the layers of the greater omentum. The left margin of the sac is formed by thespleen, the gastrosplenic omentum, and the splenicorenalligament. The right margin opens into the greater sac (themain part of the peritoneal cavity) through the epiploicforamen.

BOUNDARIES OF THE EPIPLOIC FORAMEN

• Anteriorly: Free border of the lesser omentum, the bileduc t, the hepa tic artery, and the po rtal vein.

• Posteriorly: Inferior vena cava.• Superiorly: Caudate process of the caudate lobe of the

liver.• Inferiorly: First part of the duoden um.


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CHAPTER2 Abdomen 47

liver

lesser omentum

stomach

transverse colon

umbilicus

greater omentum

uterus bladder

diaphragmaorta

lesser sac

pancreas

transverse mesocolon

third part of duodenummesentery

ileum

greater sac

rectouterine pouch(pouch of Douglas)

rectum

vagina

falciform ligament

hepatic artery bile duct

liver

portal vein

entrance intolesser s ac

inferior vena cava

aorta lesser sac

left kidney

splenicorenal ligament

spleen

gastrosplenic omentum

stomach

greater saclesser omentum

A

BFigure 2-9 A. Sagi tta l sect ion of a fem ale abd ome n showing the arrangem ent of the per i toneum .B. Transverse sect ion (as v iewed from be low) of an ab dom en sho wing the arrangeme nt of the

pe ritone um .

Peritoneal Recesses, Spaces, andGutters

DUODENAL RECESSES, CECAL RECESSES, SPACES,AND GUTTERS

Duodenal RecessesClose to the du odenojejunal junction, there may befour small pouches of peritoneum called the superior

duodenal recess, the inferior duodenal recess,the paraduodenal recess, and the retroduodenalrecess.

Ceca l Recesses

Folds of peritoneum close to the cecum produce three p eri-toneal recesses called the superior ileocecal recess, theinferior ileocecal recess, and the retrocecal recess.


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48 CHAPTER2 Abdomen

A

B

falciform ligament

left lobe of liver

ligamentum venosum

lefttriangular ligament

lesser omentum

caudate lobeinferior

vena cava

coronary ligament

bare area

right lobe of liver

hepatic veins

ligamentum venosumcaudate lobe of liver

left triangular ligament

portal vein

hepatic artery

left lobe of liver

igamentum tereswithin falciform ligament

quadrate lobe of liver

gallbladder

right lobe of liver

cystic duct joining bile duct

bile duct

right triangular ligamentcoronary ligament

Figure 2-10 A. The liver as viewe d from a bove. B. The liver as viewe d from b ehind. Note the pos i-tion o f the p eritone al reflections, the bare area s, and the pe ritonea l ligame nts.

Nerve Supply of the Pe ritone umThe parietal peritone um is supp lied for pain, temp erature,touch, and pressure by the lower six thorac ic and first lum-

ba r nerves. The pa rietal peritoneum in the pe lvis is mainlysupplied by the ob turator nerve.

P ARACOLIC G UTTERS

Paracolic gutters lie on the lateral and the medialsides of the ascending and the descending colons, re-spectively. They provide channels for the movementof infected fluid in the peritoneal cavity.

SUBPHRENIC SPACESSubphrenic spaces lie between the diaphragmand the liver, and they are called the right and leftanterior and posterior subphrenic spaces.Clinically, these spaces are important because theymay provide sites for the a ccumulation o f pus.

CLINICAL NOTES

P ERITONEAL P AIN

Pain f rom the Par ieta l Per i toneum

Because the parietal peritoneum is innervated fromsomatic nerves, pain involving this area is of the

CLINICAL NOTES


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CHAPTER2 Abdomen 49

lesser curvatures ), and two surfaces (an anterior and aposterior surface ) .

The stoma ch may be divided into the following parts:

• Fundus: This is dome -shape d and projects upward a nd tothe le ft of the card iac o rifice. It is usua lly full of gas.

• Body: This extends from the cardiac orifice to the in -cisura angularis (a constant notch in the lower part of the lesser curvature) .

• Pyloric antrum: This extends from the incisura angularisto the pylorus.

• Pylorus: This is the most tubular pa rt of the stomach. Thethick, muscular wall is called the pyloric sphincter, andthe cavity of the pylorus is called the pyloric canal.

The lesse r curvature forms the right borde r of the stom-ach and is connected to the liver by the lesser omentum.The greater curvature is much longer than the lesser cur-vature, and it extend s from the left of the cardiac orifice over the dome o f the fundus and along the left border of the stom-

ach. The gastrosplenic omentum (ligament) extends fromthe upper part of the greater curvature to the spleen. Thegreater omen tum extend s from the lower pa rt of the greater curvature to the transverse co lon.

lesser curvature

pyloric antrum pylorus

liver gallbladder

bile duct

duodenum

right colic flexure

transverse colon

ascending colon

coils of ileum

ileocecal junction

cecum

appendix

anal canal

esophagus

fundus

greater curvature

body

pancreas

left colic flexure

duodenojejunalflexure

coils of jejunum

descending colon

tenia coli

appendices epiploicae

sigmoid colonrectum

stomach

Figure 2-11 General ar rangemen t of the a bdom inal v iscera .

somatic type and can be precisely localized; it is usu-ally severe.

Pain from th e Viscera l Peri toneu m

Because the visceral peritoneum and that of themesenteries are innervated by autonomic nerves,

pa in involving these a rea s is of the visce ral type and isdull and poorly localized. Remember that stretchcaused by overdistension of a viscus or pulling on amesen tery can give rise to visceral pain.

The visceral peritoneum is supplied for stretch only by auton om ic ne rves that supp ly the visce ra or that aretraveling in the mesen teries.

GASTROINTESTINAL VISCERAStomachThe stoma ch is a dilated portion of the a limen tary can al sit-uated in the upper part of the abdomen (Fig. 2-11). It isroughly J-shaped, and it has two open ings (the cardiac andthe pyloric orifices ), two curvatures (the greater and the


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50 CHAPTER2 Abdomen

The esophagus enters the stomach at the cardiac ori-fice. No an atom ic sphin cter ca n be dem on stra ted he re,

bu t a physiologic mech an ism prevents the regurgitation of stomach contents into the esophagus.

The pyloric o rifice is formed by the pyloric ca nal. Thecircular muscle coat of the stomach is much thickerhere and forms the anatomic and physiologic pyloricsphincter.

BLOOD SUPPLY

ArteriesThe right and left gastric arteries supply the lesser curvature.The right an d left gastroep iploic arteries supply the greater curvature. Short gastric arteries derived from the splenicartery supp ly the fund us ( Fig. 2-12).

Veins

The veins drain into the portal circulation. The right and leftgastric veins drain into the portal vein. The short gastricand the left gastroepiploic veins drain into the splenic vein,and the right gastroepiploic vein drains into the superior mesen teric vein.

LYMPH DRAINAGE

The lymph vessels follow the arteries into the left and rightgastric nodes, the left and right gastroepiploic nodes, and

the sho rt gastric n ode s. All lymph from the stomach eventu-ally passes to the ce liac n odes.

NERVE SUPPLY

The sympa thetic nerve supp ly is from the celiac p lexus, and pa rasympa the tic is from the vagus nerves.

Small IntestineThe greater part of digestion and food absorption occu rs inthe small intestine, which extends from the pylorus of thestomach to the ileoceca l junction ( Fig. 2-11). The small in-testine is divided into three parts: the duodenum, the

jejunu m, and the ileum.

DUODENUM

The d uod enu m is a C-shaped tube ap proximately 10 in. (25cm) in length that curves around the he ad of the pancreas(Fig. 2-13). The duod enum begins at the pyloric sphincter o f the stomach, and it ends by becoming continuous with the

jejunu m. The first inch of the duo den um has the lesser omentum attached to its upper border and the greater ome ntum a ttached to its lower borde r. The remainde r of theduodenum is retroperitoneal.

The d uod enum is divided into four parts:

• The first part runs upward and backward on the transpy-loric p lane at the level of the first lumbar vertebra.

esophageal artery

aorta

left gastric artery

celiac artery

cystic artery

hepatic artery

right gastric artery

gastroduodenal artery

splenic artery

short gas tric arteries

left gastroepiploic artery

right gastroepiploic arterysuperior pancreaticoduodenal

artery

Figure 2-12 Arterial supp ly to the stom ach. Note that all the a rteries a re bran ches o f the ce liac artery.


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• The second part runs vertically downward. The bile andthe main pancreatic ducts pierce the medial wall approx-imately halfway down, and they unite to form an ampu llathat opens on the summit of a major duodenal papilla(Fig. 2-12). The accessory pancreatic duct (if present)opens into the duodenu m on a minor duoden al papilla,app roximately 0.75 in. (1.9 cm) ab ove the ma jor duo den al

papilla.• The third part pa sses ho rizontally in fron t of the vertebra l

column. The root of the mesentery of the small intestineand the supe rior mesenteric vessels cross this part an teri-orly.

• The fourth part runs upward and to the left to the duo-denojejunal flexure. The flexure is held in position bythe ligament of Treitz, which is attached to the right crusof the diaphragm.

Blood Supply

Arteries

The uppe r half of the duod enum is supp lied b y the supe rior panc rea ticodu oden al artery, which is a bra nch of the gastro-duodenal artery. The lower half is supplied by the inferior

pan creaticod uod ena l ar te ry, which is a branc h of thesuperior mesen teric artery.

Veins

The superior pancreaticoduodenal vein joins the portalvein. The inferior pancreaticoduodenal vein joins thesuperior mesen teric vein.

Lymph Drainage

The lymph vessels drain upward via the pancrea ticoduode-nal nodes to the gastroduodenal nodes and the celiac

nodes. They drain downward via the pancreaticoduoden alnodes to the superior mesenteric node s.

Nerve Supply

The duodenum is supplied by the sympathetic and vagusnerves via the celiac and the supe rior mesen teric plexuses.

JEJUNUM AND ILEUM

The jejunum mea sures approximately 8 ft. (2.5 m) long andthe ileum, approximately 12 ft. (3.6 m) long. The jejunum

be gins at the duode no jejuna l flexu re (Fig. 2-11) in the upper

CHAPTER2 Abdomen 51

right hepatic duct

right lobeof liver

gallbladder

fundus

body

neck

cystic ductminor duodenal papilla

accessory pancreatic duct

major duodenal papilla

second part of duodenum

left hepatic duct

left lobe of liver

spleen

common hepatic duct bile duct

body of pancreas tail of pancreas

duodenojejunalflexure

uncinate process of pancreas

main pancreatic duct

head of pancreas

Figure 2-13 The liver, biliary ducts, pancrea s, and s pleen. Note their relations hip to one an other an d to the du ode num .


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52 CHAPTER2 Abdomen

pa rt of the abdominal cavity and to the left of the midline. Itis wider in diameter, thicker walled, and redder in color than the ileum.

The coils of the ileum occ upy the lower right part of theabdominal cavity and tend to hang down into the pelvis.The ileum end s at the ileocecal junction. The coils of the je-

junum and the ileum are suspende d from the posterior ab-dom inal wall by a fan-shaped fold of peritoneum called themesentery of the small intestine.

Blood Supply

Arteries

Branches of the superior mesenteric artery (Fig. 2-14)anastomose with one another to form arcades.

Veins

The veins drain into the superior mesen teric vein.

Lymph Drainage

The lymph passes to the superior mesenteric nodes viaintermediate mesenteric nodes.

Nerve Supply

Sympathetic and vagus nerve fibers a rise from the superior mesenteric plexus.

middle colic artery

right colic artery

ileocolic artery

anterior cecal artery

appendicular artery

abdominal part of aorta

superior mesenteric artery

jejunal arteries

inferior mesenteric artery

left colic artery

ileal arteries

sigmoid arteries

superior rectal artery

Figure 2-14 The superior and inferior me sen teric arteries an d their branches.

Large IntestineThe large intestine extend s from the ileum to the a nus ( Fig.2-11). It is divided into the cecum, the appendix, the as-

MECKEL ’S D IVERTICULUM

Meckel’s diverticulum is a c ongenital an oma ly repre-senting a persistent portion of the vitellointestinalduct. It is located (if present) on the antimesenteric

bo rde r of the ileum approxima tely 2 ft. (60 cm ) fromthe ileocecal junction. It is about 2 in. (5 cm) inlength, and it occu rs in app roximately 2% of individu-als. It is important clinically because bleed ing may oc-cur from an ulcer in its mucous memb rane.

CLINICAL NOTES


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CHAPTER2 Abdomen 53

cending colon, the transverse colon, the descending colon,the sigmoid co lon, the rectum , and the anal canal. (The rec-tum and the anal canal are discussed in Chapter 3.) Themain functions of the large intestine include absorption of water, produc tion of certain vitamins, storage of und igestedfood materials, and formation and excretion of feces fromthe body.

CECUM

The cecum is a blind-ended pouch within the right iliacfossa and is completely covered with peritoneum (Fig. 2-11). At the junc tion of the cecum and the ascending colon,it is joined on the left side by the terminal pa rt of the ileum .The appendix is attached to its posteromedial surface.

Blood Supply

Arteries

Anterior and posterior cecal arteries from the ileocolicartery (Fig. 2-14), which is a branch of the superior mesen-teric artery.

Veins

The veins drain into the supe rior mesenteric vein.

Lymph Drainage

The lymph drains into the mesenteric and superior mesen-teric nodes.

Nerve Supply

Sympathetic a nd vagus ne rves, via the superior mesenteric plexus, supp ly the cecum.

ILEOCECAL VALVE

A rudimentary structure, the ileocecal valve consists of twohorizontal folds of mucous membrane that project aroundthe orifice of the ileum. The valve plays little or no part in

preventing reflux of cecal contents into the ileum . The cir-cular muscle at the lower end of the ileum (the ileocecalsphincter ) serves as a sphincter and controls the flow of con tents from the ileum into the colon. The smooth muscletone is reflexively increased when the cecum is distended;the hormone gastrin, which is produced by the stomach,

causes relaxation of the muscle tone.

APPENDIX

The append ix (Fig. 2-11) is a na rrow, muscular tube with alarge amount of lymphoid tissue in its wall. It is attached tothe posteromedial surface of the cecum ap proximately 1 in.(2.5 cm) below the ileocecal junction. It has a complete

pe ritonea l covering, which is attached to the me sentery of the small intestine by a short mesentery of its own calledthe mesoappendix. The mesoappendix contains theappendicular vessels and nerves.

The b ase of the ap pendix can b e located inside the ab-dom en by tracing the teniae coli of the cec um and then fol-lowing them to the ap pendix, where they converge to forma con tinuous mu scle co at.

Blood Supply

Arteries

Appendicu lar artery is a branch of the posterior cecal artery(Fig. 2-14).

Veins

The veins drain into the posterior ceca l vein.

Lymph Drainage

The lymph drains into nodes in the mesoappendix andeventually into the superior mesen teric lymph no des.

Nerve Supply

The appendix is supplied by the sympathetic and vagusnerves from the superior mesen teric plexus.

ASCENDING COLON

The ascending colon is approximately 5 in. (13 cm) inlength and extends upward from the cecum to the inferior

VARIABILITY OF P OSITION OF APPENDIX ANDTHE D IAGNOSIS OF APPENDICITIS

The inconstancy of the position of the appendixshould be borne in mind when attempting to diag-nose an appendicitis. A retrocecal appendix, for ex-amp le, may lie be hind the ce cum, and it may be diffi-cult to elicit tend erness on palpation in the right iliacregion. An appendix han ging down in the pe lvis mayresult in absent abdominal tenderness in the rightlower quadrant but deep tenderness may be experi-enc ed just above the symphysis pub is. Rectal or vagi-nal examination may reveal tenderness of the peri-toneum in the p elvis on the right side.

CLINICAL NOTES

P AIN OF APPENDICITIS

Visceral pain in the appendix is produced by disten-

tion of its lumen or spasm of its muscle. The afferent pa in fibers en ter the spin al co rd at the level of thetenth thoracic segment, and a vague referred pain isfelt in the region of the umbilicus. Later, the pa in shiftsto where the inflamed appendix irritates the parietal

pe riton eu m, an d then the pa in is precise, severe,and localized.

CLINICAL NOTES


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54 CHAPTER2 Abdomen

surface o f the right lobe o f the liver ( Fig. 2-11). Here, it turnsto the left (forming the right colic flexure ) and becomescon tinuous with the transverse co lon. The peritoneum c ov-ers the front and the sides of the a scend ing colon, binding itto the posterior abdominal wall.

Blood Supply

Arteries

The area is supplied by the ileocolic and right colic bra nches of the superior mesen teric arte ry (Fig. 2-14).

Veins

The veins drain into the superior mesen teric vein.

Lymph Drainage

The lymph drains into the co lic lymph and superior mesen-teric nodes.

Nerve SupplySympathetic an d vagus nerves from the superior mesen teric

plexus supp ly the area .

TRANSVERSE COLON

The transverse colon is approximately 15 in. (38 cm) inlength and passes across the ab dome n, occupying the u m-

bilical and the hypogastric regions (Fig. 2-11). It begins atthe right colic flexure b elow the right lobe of the liver an dhangs downward, suspended by the transverse mesocolonfrom the pancreas. It then ascends to the left colic flexure

be low th e spleen . The left colic flexure is higher than theright co lic flexure and is held up by the phrenicocolic lig-ament. The transverse mesocolon (or mesentery of thetransverse colon) is attached to the superior border of thetransverse colon an d suspend s it from the pa ncrea s; the pos-terior layers of the greater omentum are attached to theinferior bo rder.

Blood Supply

Arteries

The proximal two thirds of the transverse colon is supplied by the middle co lic arte ry (Fig. 2-14), which is a bra nc h of the superior mesenteric artery. The distal one third is sup-

plied by the le ft co lic artery, which is a branch o f the in ferior mesen teric artery.

Veins

The veins drain into the superior and the inferior mesentericveins.

Lymph Drainage

The p roximal two thirds drain into the co lic nodes an d intothe superior mesenteric nodes. The distal one third drainsinto the colic nodes and then the inferior mesenteric nod es.

Nerve Supply

The proximal two thirds is innervated by the sympatheticand the vagal nerves through the superior mesenteric

plexus. The dista l one th ird is inn ervate d by the sympa the ticand the parasympathetic pelvic splanchnic nerves through

the inferior mesenteric plexus.

DESCENDING COLON

The descending colon is approximately 10 in. (25 cm) inlength and extends downward from the left colic flexure tothe pelvic brim, where it becomes continuous with the sig-moid colon (Fig. 2-11). The peritoneum covers the front andthe sides and also binds it to the posterior abdominal wall.

Blood Supply

Arteries

Left colic branch and sigmoid branches of the inferior mesenteric artery (Fig. 2-14) supply the area.

Veins

The veins drain into the inferior mesen teric vein.

Lymph Drainage

The lymph passes to the colic and inferior mesentericnodes.

Nerve Supply

Sympathetic and parasympathe tic pelvic splanc hnic ne rvesthrough the inferior mesen teric plexus supply the area .

SIGMOID COLON

The sigmoid co lon is 10 to 15 in. (25 to 38 cm) in length and be gins as a con tinuation of the de scend ing co lon in front of the pelvic brim (Fig. 2-11). Below, it becomes continuouswith the rectum in front o f the third sac ral vertebra. It hangsdown into the pelvic cavity in the form of a loop and isattached to the posterior pelvic wall by the fan-shapedsigmoid mesocolon.

Blood Supply

ArteriesSigmoid branches of the inferior mesenteric artery (Fig.2-14) supply the sigmoid colon.

Veins

The veins drain into the inferior mesen teric vein.

Lymph Drainage

The lymph drains into the colic and inferior mesentericnodes.


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CHAPTER2 Abdomen 55

Nerve Supply

Sympathetic and parasympathetic nerves through theinferior hypogastric plexuses supp ly the area.

Difference s be twee n Small and LargeIntestinesEXTERNAL DIFFERENCES• The small intestine is more mo bile ( except for the duod e-

num) , whereas the ascending and the d escending parts of the co lon are fixed.

• The small intestine has a mesentery (except for the duo-den um) , wherea s the large intestine is retroperitoneal (ex-cep t for the transverse colon and sigmoid colon) .

• The d iameter of the full small intestine is smaller than thatof the full large intestine.

• In the small intestine, the longitudinal muscle forms a con -tinuous layer around the gut, whereas in the large intestine(except for the appendix, rectum, and anal canal), thelongitudinal muscle forms three bands (the teniae coli ) .

• The small intestine ha s no fatty tags attache d to itswall, whereas the large intestine ha s the appendicesepiploicae.

• The wall of the sma ll intestine is smooth, whereas the wallof the large intestine is sacculated.

INTERNAL DIFFERENCES

• The muc ous membrane of the small intestine has perma-nent folds (the plicae circulares ), whereas the largeintestine does not.

• The muc ous memb rane of the small intestine has Peyer’spatches, whereas the large intestine has solitary lymphfollicles.

• The m uco us memb rane of the small intestine has villi,whereas the large intestine d oes no t.

ACCESSORY ORGANS OF THEGASTROINTESTINAL SYSTEM

LiverThe largest organ in the body, the liver (Fig. 2-10) occupiesthe upper part of the abdominal cavity just beneath the di-aphragm. The liver may be divided into a large right lobeand a small left lobe by the atta chment of the periton eum of the falciform ligament (Fig. 2-10). The right lobe is further subdivided into a quadrate lobe and a caudate lobe by thegallbladder, the fissure for the ligamentum teres, the inferior vena ca va, and the fissure for the ligamentum venosum.

The liver is completely surrounded by a fibrous cap sule bu t is only partia lly covered with pe ritoneu m.

PORTA HEPATIS, FISSURES, GROOVES, AND FOSSAE

Porta HepatisThe porta he patis (or hilus) of the liver is on the p osteroin-ferior surface of the liver (Fig. 2-10). The upper part of the

lesser omentum is attached to its margins. Within the portahepatis are the right and left hepatic ducts; the right and left

bra nches of the hepa tic arte ry; and the po rtal vein, ne rves,and lymph vessels.

Fissure for the Ligamentum Teres

The fissure that contains the ligamentum teres lies be twee n the left lobe and the quad rate lobe ( Fig. 2-10). Theligamentum teres is the fibrous remains of the umbilicalvein.

Fissure for the Ligamentum Venosum

The fissure that co ntains the ligamentum venosum lies be -tween the left lobe and the c audate lob e ( Fig. 2-10). The lig-amentum venosum is the fibrous remains of the ductusvenosus, and the upper part of the lesser omentum isattached to the margins of the fissure.

Groove for the Inferior Vena CavaThe groove for the inferior vena cava lies between the rightlobe and the caudate lobe (Fig. 2-10). Here, the hepaticveins join the inferior vena c ava.

Fossa for the Gallbladder

The fossa for the gallbladder lies between the right lobe andthe quadrate lobe (Fig. 2-10). There is no peritoneum be-tween the gallbladder and the right lobe of the liver.

PERITONEAL LIGAMENTS

Falc iform LigamentThe falciform ligament is a two-layered fold of peritoneumthat attaches the liver to the diaphragm ab ove and to the an -terior abdominal wall below (Fig. 2-10). It has a sickle-shaped free margin that contains the ligamentum teres(the rem ains of the umbilical vein).

Coronary Ligament

The coronary ligament attaches the liver to the diaphragm(Fig. 2-10). The peritoneal layers forming the ligament arewidely separated, leaving a “bare area” of liver devoid of a

pe ritonea l covering.

Right Triangular LigamentThe right triangular ligament is a V-shaped fold of peri-toneum formed by the right extremity of the co ronary liga-ment (Fig. 2-10). It con nects the posterior surface o f the rightlobe o f the liver to the d iaphragm.

Left Triangular Ligament

The left triangular ligament is formed b y the re flec tion of the pe ritoneum from the uppe r surface of the left lobe of theliver to the d iaph ragm ( Fig. 2-10).


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56 CHAPTER2 Abdomen

LESSER OMENTUM

The upper end of the lesser ome ntum is attached to the ma r-gins of the po rta hepatis and the fissure for the ligame ntumvenosum. It is attached be low to the lesser curvature of thestomach (Fig. 2-9).

BLOOD SUPPLY

The hepatic artery, which is a branch of the celiac artery,divides into right and left terminal branches that enter the

po rta he patis. The portal vein divides into right and left ter-minal branches that enter the porta hep atis behind the ar-teries. Three or more hepatic veins emerge from the po ste-rior surface of the liver and d rain into the inferior vena cava.

LYMPH DRAINAGE

The lymph enters node s in the po rta hepatis and then d rainsinto the celiac nodes. Some lymph passes through the

diaphragm to enter the posterior mediastinal nodes.

NERVE SUPPLY

The liver is supplied by sympathetic and parasympathetic(vagal) fibers from the celiac plexus. The left vagus nervegives rise to a large h epa tic branc h tha t travels directly to theliver.

GallbladderThe gallbladde r is a pe ar-shaped sac lying on the u nde rsur-face of the liver (Fig. 2-10). It is divided into a fundus, abody, and a neck. It ha s a cap acity of approximately 30 mL,and it both stores and concentrates bile by absorb ing water.The n eck is continuous with the c ystic duct.

BLOOD SUPPLY

ArteriesThe cystic artery, which is a branch of the right hepaticartery, supplies the gallbladd er.

Veins

The cystic vein drains into the portal vein.

LYMPH DRAINAGEThe lymph pa sses to the cystic lymph node n ear the neck of the gallbladd er, then to the hepatic nod es, and finally to theceliac n odes.

NERVE SUPPLY

The gallbladde r is supplied by sympa thetic and parasympa-thetic vagal fibers from the celiac plexus. The gallbladder contracts in response to the hormone cholecystokinin,which is produce d by the mucous mem brane of the du ode-num on the arrival of food from the stoma ch.

Bile Ducts

HEPATIC DUCTSThe right and the left hepatic ducts emerge from theright and left lobes of the liver in the porta hepatis. Eachhepatic duct is formed by the union of small bile ducts(bile canaliculi) within the liver. The common hepaticduct is formed by the union of the right and the left hep-

atic ducts, and it is joined on the right side by the cysticduc t from the gallbladde r to form the bile du ct ( Fig. 2-10).

CYSTIC DUCT

The cystic duct is an S-shaped duct that connects the neck of the gallbladder with the common hepatic duct to formthe b ile duct ( Fig. 2-10). The muc ous me mbran e is raised toform a spiral fold (spiral valve) that keeps the lumen con-stantly open.

BILE DUCT (COMMON BILE DUCT)

The bile duct is formed by the union of the cystic with thecommon hepatic duct (Fig. 2-13). It runs in the right freemargin of the lesser omentum with the portal vein behindand the he patic artery on the left. It descends in front of theopening into the lesser sac and passes behind the first partof the duodenum and then the head of the pancreas. The

bile duc t end s below by pierc ing the med ial wall of the d uo -denum approximate ly ha lfway down its length ( Fig. 2-13). Itis usually joined by the main p anc reatic duc t, and, together,they open into a sma ll amp ulla in the du odenal wall calledthe ampulla o f Vater. The a mpulla opens into the lumen of the duo denum by means of a small papilla called the majorduodenal papilla (Fig. 2-13). The terminal parts of both

G ALLSTONES

Gallstones are usually asymptomatic; however, they

can give rise to gallstone colic or produce acutecholecystitis. Biliary colic is usually caused by spasmof the smooth muscle of the wall of the gallbladder.Afferent nerve fibers ascend through the celiac p lexusand the greater splanc hnic ne rves to the thoracic seg-ments of the spinal cord. Referred pain is felt in theright upper qu adran t of the epigastrium ( T7, 8, and 9dermatomes).

ACUTE CHOLECYSTITIS

Inflamm ation o f the gallbladder may ca use irritationof the subdiaphragmatic parietal peritoneum, whichis supp lied in part by the ph renic ne rve ( C3, 4, and 5).

This may give rise to referred pain over the shoulde r, be cause the skin in this region is supp lied b y the sup r-aclavicular nerves (C3 and 4).

CLINICAL NOTES


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CHAPTER2 Abdomen 57

ducts and the amp ulla are surrounded by circular smoothmuscle called the sphincter of Oddi. Occasionally, the

bile an d the p ancreatic du cts open sepa rate ly into the d uo-denum.

PancreasThe pa ncreas is both an exocrine an d an endoc rine gland.It is an elongated structure that lies on the posterior ab-dominal wall behind the stomach and behind the peri-toneum. It may be divided into a head, a neck, a body, anda tail (Fig. 2-13). The head is disc shaped and lies withinthe concavity of the C-shaped duodenum. The uncinateprocess is a projection to the left from the lower part of thehead behind the superior mesenteric vessels. The neck isnarrow and connects the head to the body; it lies in frontof the beginning of the portal vein. The body pa ssesupward and to the left across the midline, and the tailextends to the hilus of the spleen in the splenicorenal

ligament.

PANCREATIC DUCTS

The main pancreatic duct opens into the second p art of the duodenum with the bile duct on the major duodenal

papilla (Fig. 2-13). The main duc t also some times drains sep -arately into the duod enum. The accessory duct (if present)drains the up per part of the head and opens into the duo-denum on the minor duodenal papilla.

BLOOD SUPPLY

ArteriesThe splenic artery and the superior and inferior pancreati-coduodenal arteries supply the pancreas.

Veins

The p anc reatic veins drain into the p ortal vein.

LYMPH DRAINAGE

The lymph nodes are situated along the arteries and draininto the celiac a nd the superior mesenteric n odes.

NERVE SUPPLY

Sympathetic and parasympathetic vagal nerve fibers fromthe celiac plexus supply the pancreas.

SpleenThe spleen is the largest single mass of lymphoid tissue inthe b ody (Fig. 2-13). It lies just ben eath the left half of the d i-aph ragm close to the ninth, the ten th, and the e leventh ribs.The spleen is ovoid in shape, with a notched anterior bor-der. It is surrounded by peritoneum that passes from thehilus to the stomach as the gastrosplenic omentum (liga-men t) and to the left kidne y as the splenicorenal ligament

(Fig. 2-9). The gastrosplenic om entum con tains the sho rt gas-tric and the left gastroepiploic vessels, and the splenicorena lligament contains the splenic vessels and the tail of the

panc reas.

BLOOD SUPPLYArteryThe large splenic artery, which is a branch of the celiacartery (Fig. 2-12), supp lies the spleen .

Vein

The splenic vein joins the supe rior mesenteric vein to formthe po rtal vein.

BLOOD SUPPLY OF THEGASTROINTESTINAL VISCERA

The celiac artery is the artery of the foregut, and it supplies the gastrointe stinal trac t from the lower third of theesophagus down to the middle of the second part of theduodenum (Fig. 2-12). The superior mese nteric artery isthe a rtery of the m idgut, and it supplies the gastrointestinaltract from the middle of the second part of the duodenumto the distal third of the transverse colon (Fig. 2-14). The in -ferior mese nteric artery is the artery of the hindgut, andit supplies the large intestine from the distal third of thetransverse colon to halfway down the anal canal.

Celiac Artery (Trunk)The celiac artery is a short, large artery that arises from thefront of the abdominal aorta as it emerges through the di-aphragm (Fig. 2-12). It has three terminal branches: the leftgastric, the splenic, an d the h epa tic arteries.

LEFT GASTRIC ARTERY

The left gastric arte ry is a small artery that runs to the c ard iacend of the stomach, gives off a few esophageal branches,and then turns to the right along the lesser curvature of thestomach. It anastomoses with the right gastric artery.

SPLENIC ARTERY

The splenic artery is the largest branch of the celiac trunk,and it runs to the left in a wavy course along the upper bo r-der of the pancreas and behind the stomach. On reachingthe left kidney, it enters the splen icorenal ligame nt and runsto the hilum of the spleen .

Branches

• Pancreatic branches .• Left gastroepiploic artery: This arises near the hilum of

the spleen and reaches the greater curvature of the stom-ach in the gastrosplenic omentum. In the greater omen-tum, it passes to the right along the greater curvature of the


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58 CHAPTER2 Abdomen

stomach. It anastomoses with the right gastroepiploicartery.

• Short gastric arteries: Five o r six in number, these pa ssto the fundus of the stomach in the gastrosplenic omen-tum. They anastomo se with the left gastric artery and theleft gastroepiploic artery.

HEPATIC ARTERY

The hepatic artery* runs forward and ascends within thelesser omen tum ( Fig. 2-12). It lies in front of the ope ning intothe lesser sac, and it is placed to the left of the b ile du ct andin front of the portal vein. At the po rta hepatis, it divides intoright and left branches that supply the corresponding lobesof the liver.

Branches

• Right gastric artery: This runs to the pylorus and then tothe left in the lesser omen tum along the lesser curvature of the stomach. It anastomoses with the left gastric artery.

• Gastroduode nal artery: This descends behind the first pa rt of the d uode nu m. It divides into the right gastroepi-ploic artery, which runs along the greater curvature of the stomach in the greater omentum, and the superiorpancreaticoduodenal artery, which d escends betweenthe second part of the duodenum and the head of the

panc reas.• Right and left hepatic arteries: These run to the right

and the left lobes of the liver. The right he patic artery usu-ally gives off the cystic artery, which runs to the nec k of the gallbladder.

Superior Mesenteric ArteryThe superior mesenteric artery arises from the front of theabdominal aorta behind the neck of the pancreas (Fig. 2-14). It runs downward in front of the unc inate proc ess of the

panc reas and in front of the third pa rt of the duod enum . Itthen continues downward to the right in the root of themesen tery of the small intestine.

BRANCHES

• Inferior pancreaticoduode nal artery: This passes tothe right as a single or a double branch along the upper

bo rde r o f the third pa rt o f the duod enum an d be low the

head of the pancreas.• Middle colic artery: This runs into the transverse me so-

colon to supply the transverse colon (Fig. 2-14). It dividesinto a right branch , which an astomoses with the right colicartery, and a left branc h, which an astomoses with the leftcolic artery.

• Right colic artery: This is often a branc h o f the ileocolicartery (Fig. 2-14). It passes to the right to supply theascending colon.

• Ileoc olic artery: This passes downward and to the right(Fig. 2-14). It gives rise to a superior branch, which anas-tomoses with the right colic artery, and an inferiorbranch, which anastomoses with the end of the superior mesenteric artery. The inferior branch gives rise to theanterior and the posterior cecal arteries; the appen-dicular artery is a branch of the p osterior cec al artery.

• Jejunal and ileal branches: There are 12 to 15 of these,which arise from the left side of the superior mesentericartery (Fig. 2-14). Each artery divides into branches thatunite with adjacent branches to form arcades. Small,straight branch es supp ly the intestine.

Inferio r Mesenteric ArteryThe inferior mesenteric artery arises from the abdominal

aorta approximately 1.5 in. (3.8 cm) above its bifurcation(Fig. 2-14). This artery runs downward and to the left, and itcrosses the left common iliac artery. Here, its name ischa nged to the supe rior rectal artery.

BRANCHES

• Left colic artery: This divides into ascending and de-scend ing branches that supply the distal third of the trans-verse co lon, the left colic flexure, and the up per pa rt of thedescending colon (Fig. 2-14).

• Sigmoid arteries: Two or three in number, these supplythe descending and the sigmoid colon (Fig. 2-14).

• Superior rectal artery: This is a continuation of the infe-rior mesenteric artery, and it descends into the pelvis be-hind the rectum (Fig. 2-14). It supplies the rectum andthe upper half of the ana l canal, and it anastomoseswith the midd le and the inferior rectal arteries that arisefrom the internal iliac and the internal pudendal arteries,respectively.

Marginal ArteryThe colic arteries anastomose around the concave marginof the large intestine, where they form a single arterial trunk called the marginal artery. The marginal artery begins atthe ileocolic junction and ends at the junction of the

sigmoid c olon and the rectum.

Portal Venous System

PORTAL VEINThe portal vein is approximately 2 in. (5 cm) in length andis formed b ehind the n eck of the pancreas by the union of the superior mesenteric and the splenic veins (Fig. 2-15). Itascends to the porta hepatis behind the first part of the duo-den um a nd in the free margin of the lesser omentum. In the

po rta he pa tis, it then divide s into right an d left termina l bra nc hes.

*The hepa tic artery is sometimes divided into the common he paticartery, which extends from its origin to the gastrodu oden al branch ,and the hepatic artery proper, which is the remainder o f theartery.


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CHAPTER2 Abdomen 59

The portal vein drains blood from the gastrointestinaltract (from the lower end o f the e sophagus to ha lfway downthe anal canal) as well as from the pancreas, the gall-

bladd er, the b ile duc ts, and the sp leen.

TRIBUTARIES

• Splenic vein: This leaves the spleen and unites with thesuperior mesenteric vein beh ind the n eck of the pa ncreas

to form the portal vein (Fig. 2-15). It receives the short gas-tric, the left gastroepiploic, the inferior mesenteric, andthe pancreatic veins.

• Inferior mesente ric vein: This ascends on the po sterior abdominal wall and joins the splenic vein behind the

body of the panc reas (Fig. 2-15). It rec eives the superior rectal, the sigmoid, and the left colic veins.

• Superior mesenteric vein: This ascends in the root of the mesentery of the small intestine on the right side of the

cystic veinleft branchof portal vein

inferior vena cava

ligamentum venosumesophageal vein

left gastric vein

short gastricvein leftgastroepiploicvein

splenic vein

pancreatic veins

inferior mesentericvein left colic

vein

sigmoidveins

superior rectal vein

umbilicus

ilialveins

appendicular veins

ileocolicvein

right colicvein

ligamentum teres

middle colicvein

right gastroepiploic vein

portal vein

rightgastricvein

liver

Figure 2-15 Tributaries of the portal vein.


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60 CHAPTER2 Abdomen

artery. It passes in front of the third part of the duode num,and it joins the splenic vein behind the neck of the pan-creas (Fig. 2-15). It receives the jejunal, the ileal, the ileo-colic, the right and middle colic, the inferior pancreatico-duo den al, and the right gastroep iploic veins.

• Left gastric ve in: This drains the left portion of the lesser curvature of the stomach and the distal part of the e soph-agus. It open s direc tly into the portal vein (Fig. 2-15).

• Right gastric vein: This drains the right portion of thelesser cu rvature o f the stomach. It drains directly into the

po rtal vein (Fig. 2-15).• Cystic veins: These drain the gallbladder either directly

into the liver or join with the porta l vein (Fig. 2-15).

• Renal fascia: This is a conden sation of areolar tissue out-side the perirenal fat. It encloses the kidneys and thesuprarenal glands.

• Pararen al fat: This is external to the renal fascia a nd is of-ten large in amount.

The perirenal fat, the renal fascia, and the pararenal fatsupport the kidneys and hold them in position on the

posterior abdominal wall.

RENAL STRUCTURE

The outer cortex is dark brown in color, and the inner medulla is light brown. The medulla is composed of ap-

proxima tely 12 renal pyramids, each having its base ori-ented toward the cortex and its apex (the renal papilla )

pro jecting me dia lly (Fig. 2-17). The co rtex exte nd s into themed ulla between adjacen t pyramids as the renal columns .Extending from the bases of the rena l pyramids into the c or-tex are striations c alled medullary rays.

Within the renal sinus, the upper expanded end of theureter (the renal pelvis ) divides into two or three major ca-lyces, eac h of which in turn divides into two or three minorcalyces (Fig. 2-17). Each minor calyx is indented by theapex of the renal pyramid (the renal papilla ) .

BLOOD SUPPLY

ArteryThe renal artery, which is a b ranch of the ao rta, supp lies thekidneys.

Vein

The renal vein drains into the inferior vena cava.

LYMPH DRAINAGE

The lymph drains into the lateral aortic lymph nodes aroundthe o rigin of the ren al artery.

NERVE SUPPLY

The renal sympathetic plexus supp lies the kidne ys.

UretersThe two ureters are muscular tubes that extend from the kid-neys to the posterior surface of the urinary bladder (Fig.2-16). Each ureter measures approximately 10 in. ( 25 cm) inlength and has an upper expanded end called the renal

pelvis. The renal pelvis lies within the hilus of the kidney,where it receives the ma jor ca lyces.

KIDNEYS AND URETERS

KidneysThe kidneys are paired organs that lie behind the peri-toneum h igh up on the posterior abdominal wall on either

side of the vertebral column (Fig. 2-16). The right kidney isslightly lower than the left kidney because of the large sizeof the right lobe of the liver. With contraction of the di-aph ragm during respiration, bo th kidneys move by as muc has 1 in. (2.5 cm) downward in a vertical direction. On themedial concave border of each kidney is the hilus, whichextends into a large cavity (the renal sinus ). The hilustransmits the renal pelvis, the renal artery, the renal vein,and the sympathetic nerve fibers. The kidneys have thefollowing c overings:

• Fibrous capsule: This is closely applied to its outer surface.

• Perirenal fat: This is fat that covers the fibrous capsule.

P ORTAL –S YSTEMIC ANASTOMOSES

Portal–systemic anastomoses are important in pa-

tients with cirrhosis of the liver and in whom the p or-tal vein may be o bstructed.

• At the lower third of the esopha gus, the esophageal branc hes of the le ft gastric vein ( the porta l tribu tary)anastomose with the esophageal veins draining themiddle third of the esophagus into the a zygos veins(the systemic tributaries).

• Halfway down the an al canal, the superior rectalveins (the portal tributaries) d raining the u ppe r half of the an al canal anastomose with the m iddle andthe inferior rectal veins (the systemic tributaries).

• The paraumbilical veins connect the left branchof the p ortal vein with the supe rficial veins of the an-

terior ab dom inal wall (the systemic tributaries). The pa raumb ilical vein s travel in th e falciform ligamen t,and they accompan y the ligamentum teres.

• The veins of the ascending and descending colon,the duod enum, the pa ncreas, and the liver (the po r-tal tributaries) anastomose with the renal, the lum-

ba r, and th e ph ren ic veins ( the system ic tributaries).

CLINICAL NOTES

URETERIC CONSTRICTIONS AND STONESUreteric stones may be arrested at the following sites:

• Where the renal pelvis joins the ureter.• Where the ureter is kinked as it crosses the pelvic

brim to ente r the pe lvis.• Where the ureter pierces the bladder wall.

CLINICAL NOTES


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CHAPTER2 Abdomen 61

BLOOD SUPPLY

Arteries• Upper en d: The renal artery.• Middle portion: The testicular or the ovarian artery.• Inferior end: The superior vesical artery.

VeinsThe veins of the kidney co rrespond to the relevant arteries.

LYMPH DRAINAGE

The lymph d rains into the lateral aortic and iliac nodes.

NERVE SUPPLY

The renal, testicular (or ovarian), and hypogastric plexusessupply the kidney.

right kidney

right ureter

psoas

urinary bladder rectum

external iliac artery

common iliac artery

aorta

renal pelvis

left kidney

suprarenal gland

Figure 2-16 Posterior abdom inal wall and the kidne ys and ureter in situ. Arrows indicate three

s ites where the ure ter is na rrowed.

R ENAL P AIN

Renal pain varies from a dull ache to a severe pain inthe flank that ma y radiate downward into the lower ab -dom en. Renal pain ca n result from stretching of the kid-ney capsule or spasm of the smoo th muscle in the renal

pe lvis. Afferent nerve fibers ascend throu gh the renal plexus and reach the spina l cord through the lowestsplanch nic nerve and the sympathetic trunk. They en-ter the spina l cord a t the level of T12. Pain is comm onlyreferred along the distribution of the subcostal nerve(T12) to the flank and the anterior abdominal wall.

R ENAL COLICIn renal colic, strong peristaltic waves of contraction

pass down the urete r in an attemp t to pa ss a stone on-ward. The afferent nerves from the ureter enter thespinal cord at segments T11 and 12 and L1 and 2. Thespasm of the smooth muscle of the ureter causes anagonizing co licky pain, which is referred to the skin ar-eas that are supplied by these segments of the spinalcord—na mely, the flank, loin, and groin.

CLINICAL NOTES


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62 CHAPTER2 Abdomen

cortex

medulla

renal column

pyramid

renal papilla

medullary rays

capsule

minor calyx

major calyces

renal pelvis

ureter

Figure 2-17 Longitudinal section throu gh the kidne y show ing the cortex, the m edu lla, the pyra-mids, the ren al papillae, and the calyces.

SUPRARENAL (ADRENAL) GLANDS

The two suprarenal glands are located close to the upper po les of the kidneys on the p oste rior abdo minal wall (Fig. 2-16). They are retroperitoneal and surrounded by renal fas-cia, but they are separated from the kidneys by the perirena lfat. Each gland has a yellow-colored cortex and a dark

bro wn medulla.

Blood Supply

ARTERIESBranch es from the inferior phren ic artery, the ao rta, and therenal arteries supply these glands.

VEINS

There is a single vein on e ach side. The right suprarenal veindrains into the inferior vena cava; the left suprarenal veindrains into the left renal vein.

Lymph DrainageThe lymph d rains into the lateral aortic nod es.

Nerve Supply Numerous pre ganglionic sympathetic ne rves from splanch-nic nerves supply the suprarenal glands. The majority of

these fibers end on cells in the suprarena l medu lla.

AORTA AND INFERIOR VENA CAVA

Abdominal AortaThe a orta en ters the abd omen through the aortic ope ningof the diaphragm in front of the twelfth thoracic vertebra(Fig. 2-18). It descends on the anterior surfaces of the

bo die s of the lumba r vertebra e, and it divides into thetwo common iliac arteries in front of the fourth lumbar vertebra.


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CHAPTER2 Abdomen 63

BRANCHES

• Three an terior visceral branches: the celiac artery,superior mesenteric artery, and inferior mesentericartery.

• Three lateral visceral branches: the suprarena l artery, re-

nal a rtery, and testicular o r the ovarian artery.• Five lateral abdom inal branches: the inferior phrenicartery and four lumba r arteries.

• Three terminal arteries: two common iliac arteries and themed ian sacral artery.

Common Iliac ArteriesThe right and the left commo n iliac arteries are the terminal

bra nches of the abd om inal aorta (Fig. 2-18). They run down -ward an d laterally to end opposite the sacroiliac joint by di-viding into the external an d the internal iliac arteries. At the

bifurcation, the co mm on iliac artery is crossed ante riorly bythe ureter on each side.

Inferior Vena CavaThe inferior vena cava is formed by the union of the com-mon iliac veins at the level of the fifth lumbar vertebra (Fig.2-18). It ascends on the right side of the aorta, pierces thecentral tendon of the diaphragm at the level of the eighth

thoracic vertebra, and drains into the right atrium of theheart.

TRIBUTARIES

• Two anterior visceral tributaries (the he patic veins).• Three lateral visceral tributaries: the right suprarenal vein

(the left vein drains into the left renal vein), renal veins,and right testicular or ovarian vein (the left vein drains intothe left renal vein).

• Five lateral abdom inal wall tributaries: the inferior phrenicvein and four lumba r veins.

• Three veins of origin: two comm on iliac veins and themedian sacral vein.

inferior vena cava

hepatic veins

renal vein

testicular artery

external iliac artery

inferior epigastric artery

median sacral artery

internal iliac artery

common iliac artery

inferior mesenteric arterylumbar arteries

renal artery

superior mesenteric artery

suprarenal arteryceliac artery

sympathetic trunk

cisterna chyli

inferior phrenic artery

suprarenal vein

deep circumflex iliac artery

Figure 2-18 The aorta an d the inferior vena ca va.


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subcostal nerve


ilioinguinal nerve

genitofemoral nerve

lateral cutaneousnerve of the thigh

femoral nerve

T12

L1

L2

L3

L4

to lumbosacral trunk

obturator nerveA

B

subcostal nerve


ilioinguinal nerve

lateral cutaneousnerve of the thigh

T12

L1

L2

L3

L4

L5

sacrum

femoral nerve

obturator nerve

iliacus muscle

psoas muscle

quadratus lumborummuscle

genitofemoral nerve

lumbosacral trunk

Figure 2-19 A. The lumbar plexus and i ts m ain branches . B. The lumbar plexus and i ts brancheson the po sterior abd om inal wall.

64


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CHAPTER2 Abdomen 65

LYMPHATICS ON THE POSTERIOR ABDOMINAL WALL

Lymph NodesThe lymph nodes form a preaortic and a right and leftlateral aortic ch ain.

PREAORTIC LYMPH NODES

The p reaortic lymph nod es are on the an terior surface of theabd ominal aorta. Their efferent vessels form the intestinaltrunk, which drains into the cisterna chyli. These n ode s aredivided into the celiac, the superior mesenteric, and theinferior mesenteric groups, which lie close to the originsof these arteries.

LATERAL AORTIC (PARA-AORTIC, LUMBAR) NODES

The lateral ao rtic nodes are the right and left groups that lie

alongside the abd omina l aorta. Their efferent vessels formthe right and left lumbar trunks that drain into the cis-terna chyli.

Cisterna ChyliThe thoracic duct comme nces in the abdome n as an elon-gated sac ( the cisterna chyli), which lies on the right side of the aorta in front of the first two lumbar vertebrae. The cis-terna chyli receives the intestinal trunk, the right and left

lumba r trunks, and the lymph vessels that descend from thelower part of the thorax.

NERVES

Lumbar Ple xusThe lumbar p lexus is formed by the an terior rami of the up -

pe r four lumba r n erves ( Fig. 2-19). It is situated within the psoas musc le, an d its bra nc hes emerge from the late ral bor-der, the medial border, and the anterior surface of themuscle.

BRANCHES OF THE LUMBAR PLEXUS ON THEPOSTERIOR ABDOMINAL WALL

The b ranches of the lumbar plexus and their distribution aresummarized in Table 2-2.

Table 2-2 Branches of the Lumbar Plexusand Their Distribution

Branches Distribution

Iliohypogastric External oblique, in ternal oblique,n erve ( L1) transversus a bd ominis musc les

of anterior abdo minal wall;skin o ver lower anterior abdominal wall and buttock

Ilioinguinal nerve External oblique, internal oblique,(L1) transversus abdominis muscles of

anterior ab dom inal wall; skin of uppe r medial aspec t of thigh; rootof penis and scrotum in males andmons pubis and labia majorain fema les

Lateral cutaneous Skin of anterior and lateral surfacesnerve of thigh of the thigh( L2, 3)

Genitofemoral Cremaster muscle in scrotum in male;ne rve (L1, 2) skin ove r ante rio r su rface o f th igh ;

nervous pathway for crema steric reflex

Femoral nerve Iliacus, pectineus, sartorius, quadriceps( L2, 3, 4) femoris muscles; intermediate

cutaneous branches to the skin of theanterior surface o f the thighand by sapheno us branch to the skinof the med ial side of the leg and foot;articular branches to hip andknee joints

Obturator nerve Gracilis, adductor brevis, adductor (L2, 3, 4) longus, obturator externus,

pe ctineus, addu cto r magnus (a dd uc tor po rtion) ; skin on me dia lsurface of thigh; articular

bra nc he s to hip and kne e join tsSegmental Quadratus lumborum and psoas

bra nc he s mu scle s

COMPRESSION OF THE INFERIOR VENA CAVA

During the later stages of pregnancy, the enlarged

uterus commonly presses on the inferior vena cava, produ cing ede ma of th e ankles and feet and tem po-rary varicosed veins.

Malignant retroperitoneal tumors can cause se-vere compression and eventual blockage of the infe-rior vena cava. This results in the dilatation of the ex-tensive anastomoses of the communicating veins

joining the inferior vena cava to the superior venacava. The alternative pathway for the blood to returnto the right atrium of the heart is referred to as thecaval–caval shunt. The same pathway comes intoeff

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