(Anterior abdominal wall (Skin pdf - Abdomen

natomy

asic

The abdomen is the region of the trunk that lies between

femoral artery.

the superficial external pudendal arteries, branches of the

superficial epigastric, the superficial circumflex iliac, and

tion, the skin in the inguinal region is supplied by the

and deep circumflex iliac arteries (see Fig. 4.15). In addi

flanks is supplied by branches of the intercostal, lumbar,

superior and inferior epigastric arteries. The skin of the

The skin near the midline is supplied by branches of the

Arteries

Figure 4.16.

omes and distribution of cutaneous nerves are shown in

inguinal ligament and the symphysis pubis. The dermat

includes the umbilicus and that of L1 lies just above the

over the xiphoid process. The dermatome of T10

The dermatome of T7 is located in the epigastrium

pogastric and the ilioinguinal nerves.

nerves; the 1st lumbar nerve is represented by the iliohy

racic nerves are the lower five intercostal and the subcostal

racic and the 1st lumbar nerves (see Fig. 4.16). The tho

wall is derived from the anterior rami of the lower six tho

The cutaneous nerve supply to the anterior abdominal

Nerve Supply

situated in the linea alba (see below).

site of attachment of the umbilical cord in the fetus; it is

is a scar representing the

around the trunk. The

stant and run downward and forward almost horizontally

in the skin are con

lines of cleavage

tissue. The natural

except at the umbilicus, where it is tethered to the scar

The skin is loosely attached to the underlying structures

etal peritoneum.

fascia, deep fascia, muscles, extraperitoneal fascia, and pari

The anterior abdominal wall is made up of skin, superficial

Abdominal Wall

the diaphragm above and the inlet of the pelvis below.

Structure of the Anterior

Skin

umbilicus

-
-

Blood Supply

C H A P T E R O U T L I N E

(continued)

C H A P T E R O B J E C T I V E S

the physician can often feel diseased organs that lie within

The abdominal wall is a flexible structure through which

■

Acute abdominal pain, abdominal swellings, and blunt and

penetrating trauma to the abdominal wall are common problems

facing the physician. The problems are complicated by the fact

that the abdomen contains multiple organ systems, and knowing

the spatial relationships of these organs to one another and to

the anterior abdominal wall is essential before an accurate and

complete diagnosis can be made.

■

the abdominal cavity. An intact abdominal wall is essential

for the support of the abdominal contents. A defect or

malfunction of the wall can allow the abdominal contents

provides the surgeon with a site for access to deep-lying

to bulge forward and form a hernia. The abdominal wall

diseased structures.

■

For the above reasons, the anatomy of the anterior abdominal

wall must be learned in detail. Because of its great clinical

importance, examiners ask many questions in this area.

Spleen 152

Pancreas 153

Kidneys 153

Stomach 154

Duodenum (First Part) 154

Cecum 155

Appendix 155

Ascending Colon 155

Transverse Colon 155

Descending Colon 155

Urinary Bladder and

Pregnant Uterus 155

Aorta 155

External Iliac Artery 155

Surgical Incisions

as a narrow scar, whereas one that crosses the lines will heal

If possible, all surgical incisions should be made in the lines of

cleavage where the bundles of collagen fibers in the dermis

run in parallel rows. An incision along a cleavage line will heal

as wide or heaped-up scars.

C L I N I C A L N O T E S

Infection of the Umbilicus

In the adult, the umbilicus often receives scant attention in the

shower and is consequently a common site of infection.

C L I N I C A L N O T E S

Basic Anatomy

pyramidalis.

the rectus sheath might contain a small muscle called the

abdominis to form the rectus sheath. The lower part of

of the three sheets pass forward, they enclose the rectus

cle, the rectus abdominis (Fig. 4.3). As the aponeuroses

midline anteriorly is, in addition, a wide vertical mus

oblique, and transversus (Fig. 4.2). On either side of the

exterior to interior they are the external oblique, internal

three broad thin sheets that are aponeurotic in front; from

The muscles of the anterior abdominal wall consist of

Muscles of the Anterior Abdominal Wall

ately deep to the membranous layer of superficial fascia.

layer of connective tissue covering the muscles; it lies immedi

The deep fascia in the anterior abdominal wall is merely a thin

Deep Fascia

persists as a separate layer.

The membranous layer of the superficial fascia

tos muscle.

is represented as a thin layer of smooth muscle, the

In the scrotum, the fatty layer of the superficial fascia

margin of the perineal membrane (see Fig. 4.1B).

Posteriorly, it fuses with the perineal body and the posterior

Colles’ fascia.

gins of the pubic arch; it is here referred to as

From there, it passes to be attached on each side to the mar

neum, it enters the wall of the scrotum (or labia majora).

tubular sheath for the penis (or clitoris). Below in the peri

nous layer of fascia is not attached to the pubis but forms a

inguinal ligament. In the midline inferiorly, the membra

it fuses with the deep fascia one fingerbreadth below the

membranous layer passes onto the front of the thigh, where

fascia of the back and the thorax, respectively. Inferiorly, the

above, where it becomes continuous with the superficial

The membranous layer is thin and fades out laterally and

be extremely thick (3 in. [8 cm] or more in obese patients).

with the superficial fat over the rest of the body and may

(Fig. 4.1). The fatty layer is continuous

(Scarpa’s fascia)

membranous layer

(fascia of Camper) and a deep

layer

fatty

The superficial fascia is divided into a superficial

Superficial Fascia

veins (see Fig. 4.18).

ral vein via the superficial epigastric and the great saphenous

vein via the lateral thoracic vein and below into the femo

The venous drainage passes above mainly into the axillary

Veins

115

dar-

membranous layer
(Scarpa's fascia)

line of fusion

fascia lata

position of scrotum spermatic cord

position of penis

fatty layer
(Camper's fascia)

superficial fascia

pubis

Colles' fascia

dartos muscle

urethra

membranous layer
(Scarpa's fascia)

fatty layer
(Camper's fascia)

perineal membrane

aponeurosis

of external

oblique muscle

FIGURE 4.1

taken by urine in cases of ruptured urethra.

Note the attachment of the membranous layer to the posterior margin of the perineal membrane. Arrows indicate paths

anterior abdominal wall. Note the line of fusion between the membranous layer and the deep fascia of the thigh (fascia lata).

Arrangement of the fatty layer and the membranous layer of the superficial fascia in the lower part of the

Membranous Layer of Superficial Fascia

When closing abdominal wounds, it is usual for a surgeon

and the Extravasation of Urine

The membranous layer of the superficial fascia is important

clinically because beneath it is a potential closed space that

does not open into the thigh but is continuous with the super-

ficial perineal pouch via the penis and scrotum. Rupture of the

penile urethra may be followed by extravasation of urine into

the scrotum, perineum, and penis and then up into the lower

part of the anterior abdominal wall deep to the membranous

layer of fascia. The urine is excluded from the thigh because

of the attachment of the fascia to the fascia lata (see Fig. 4.1).

to put in a continuous suture uniting the divided membra-

nous layer of superficial fascia. This strengthens the healing

wound, prevents stretching of the skin scar, and makes for a

more cosmetically acceptable result.

C L I N I C A L N O T E S

116

CHAPTeR 4

(see Fig. 4.1).

thigh, the

of the inguinal ligament is attached the deep fascia of the

versus abdominis muscles. To the inferior rounded border

ament gives origin to part of the internal oblique and trans

The lateral part of the posterior edge of the inguinal lig

(see Fig. 4.6).

pectineal ligament

the periosteum called the

lacunar ligament becomes continuous with a thickening of

(see page 460). On reaching the pectineal line, the

ral ring

femo

free crescentic edge forms the medial margin of the

on the superior ramus of the pubis (see Fig. 4.6). Its sharp,

extends backward and upward to the pectineal line

ment

lacunar liga

4.6). From the medial end of the ligament, the

(Figs. 4.2 and

inguinal ligament

ward on itself, forming the

tubercle, the lower border of the aponeurosis is folded back

Between the anterior superior iliac spine and the pubic

(Figs. 4.4 and 4.5).

round ligament of the uterus) from the margins of the ring

(or the external covering of the

external spermatic fascia

of the uterus) passes through this opening and carries the

Figs. 4.2 and 4.3). The spermatic cord (or round ligament

(see

superficial inguinal ring

tubercle. This is known as the

aponeurosis lies immediately above and medial to the pubic

A triangular-shaped defect in the external oblique

posterior free border.

most posterior fibers passing down to the iliac crest form a

are inserted by means of a broad aponeurosis. Note that the

rior half of the iliac crest (see Fig. 4.2). Most of the fibers

linea alba, the pubic crest, the pubic tubercle, and the ante

ribs and fans out to be inserted into the xiphoid process, the

sheet that arises from the outer surfaces of the lower eight

The external oblique muscle is a broad, thin, muscular

The Abdomen: Part I—The Abdominal Wall

External Oblique

-
-

fascia lata

General Appearances of the Abdominal Wall

The normal abdominal wall is soft and pliable and undergoes

inward and outward excursion with respiration. The contour is

subject to considerable variation and depends on the tone of

its muscles and the amount of fat in the subcutaneous tissue.

Well-developed muscles or an abundance of fat can prove to

be a severe obstacle to the palpation of the abdominal viscera.

C L I N I C A L N O T E S

external oblique muscle

internal oblique muscle

iliac crest

inguinal
ligament

lumbar fascia

superficial

inguinal ring

pubic

tubercle

transversus
muscle

lumbar fascia

inguinal ligament

FIGURE 4.2

External oblique, internal oblique, and transversus muscles of the anterior abdominal wall.

xiphoid process

tendinous
intersections

external
oblique
muscle

rectus muscle

inguinal
ligament

pubic tubercle

superficial inguinal ring

spermatic cord

pyramidalis

anterior
superior
iliac spine

arcuate line

internal
oblique
muscle

linea alba

linea semilunaris

FIGURE 4.3

Anterior view of the rectus abdominis muscle

shown at the level of the anterior superior iliac spine.

rectus sheath is shown. The edge of the arcuate line is

The posterior wall of the

has been partly removed, revealing the rectus muscle with

The anterior wall of the sheath

and the rectus sheath. Left.

its tendinous intersections. Right.

Basic Anatomy

upward and forward. The muscle is inserted into the lower

inguinal ligament. The muscle fibers radiate as they pass

two thirds of the iliac crest, and the lateral two thirds of the

(see Fig. 4.2). It arises from the lumbar fascia, the anterior

fibers run at right angles to those of the external oblique

lar sheet that lies deep to the external oblique; most of its

The internal oblique muscle is also a broad, thin, muscu

117

Internal Oblique

borders of the lower three ribs and their costal cartilages,
the xiphoid process, the linea alba, and the

sis pubis.

symphy

The internal oblique has a lower free border that arches
over the spermatic cord (or round ligament of the uterus)

crest and the pectineal line. Near their insertion, the low

and then descends behind it to be attached to the pubic

est tendinous fibers are joined by similar fibers from the

cremaster

with it some of the muscle fibers that are called the

passes under the lower border of the internal oblique, it carries

As the spermatic cord (or round ligament of the uterus)

the linea alba, but it has a lateral free border.

is attached medially to

conjoint tendon

4.7 and 4.8). The

transversus abdominis to form the conjoint tendon (Figs.

fascia transversalis

transversus

internal oblique

external oblique

remains of
processus vaginalis

vas deferens

external spermatic fascia

cremasteric fascia

internal spermatic fascia

testis

superficial inguinal ring

conjoint tendon

urachus

extraperitoneal fat

peritoneum

obliterated umbilical artery

inferior epigastric vessels

deep inguinal ring

fatty layer of

superficial fascia

(fascia of Camper)

membranous layer of superficial fascia

skin of scrotum

dartos muscle

external spermatic fascia

cremasteric fascia

internal spermatic fascia

tunica vaginalis

conjoint tendon

skin

FIGURE 4.4

skin and superficial fascia of the abdominal wall and scrotum have been included, and the tunica vaginalis is shown.

The

Continuity of the different layers of the anterior abdominal wall with coverings of the spermatic cord.

superficial inguinal ring

aponeurosis of
external oblique

external
spermatic fascia

cremasteric fascia

internal
spermatic fascia

dartos muscle

skin of scrotum

tunica vaginalis

superficial fascia

appendix of testis

epididymis

vas deferens

testicular artery

FIGURE 4.5

Scrotum dissected from in front. Note the

spermatic cord and its coverings.

118

CHAPTeR 4

The Abdomen: Part I—The Abdominal Wall

rectus muscle

lacunar ligament

inguinal ligament

pectineal ligament

internal

oblique

muscle

external

oblique

muscle

transversus

muscle

quadratus lumborum

muscle

iliolumbar ligament

posterior superior

iliac spine

crest of ilium

anterior superior

iliac spine

pubic tubercle

symphysis pubis

sacrum

FIGURE 4.6

Bony pelvis viewed from above. Note the attachments of the inguinal, lacunar, and pectineal ligaments.

cremaster muscle

conjoint tendon

aponeurosis of external oblique muscle

pubic crest

pubic tubercle

lacunar ligament

inguinal ligament

anterior superior iliac spine

iliopectineal line

pectineal line

pectineal

ligament

linea alba

internal oblique muscle

transversus muscle

spermatic cord

FIGURE 4.7

achment of the conjoint tendon to the pubic crest and the adjoining

Anterior view of the pelvis showing the att

part of the pectineal line.

Basic Anatomy

119

external
oblique

femoral sheath

femoral artery

lymphatic vessels

ilioinguinal nerve

pubic tubercle

spermatic cord

symphysis
pubis

superficial
inguinal
ring

linea alba

iliohypogastric nerve

inferior epigastric

artery

deep inguinal
ring

fascia transversalis

conjoint
tendon

internal
oblique

ilioinguinal
nerve

cremaster
muscle

femoral vein

pectineal
line

pubic crest

transversus muscle

fascia transversalis

inferior
epigastric
artery

pubic tubercle

spermatic cord

FIGURE 4.8

Inguinal canal showing the arrangement of the external oblique muscle

inguinal ring lies lateral to the inferior epigastric artery.

oblique and the internal oblique and the posterior wall is formed by the fascia transversalis and the conjoint tendon. The deep

Note that the anterior wall of the canal is formed by the external

and the fascia transversalis

transversus muscle

(A), the internal oblique muscle (B), the

(C),

(D).

120

CHAPTeR 4

the lumbar fascia, the anterior two thirds of the iliac crest,

six costal cartilages (interdigitating with the diaphragm),

ward (see Fig. 4.2). It arises from the deep surface of the lower

to the internal oblique, and its fibers run horizontally for

The transversus muscle is a thin sheet of muscle that lies deep

Transversus

term used to describe the cremaster muscle and its fascia.

is the

cremasteric fascia

(see Figs. 4.7 and 4.8). The

muscle

The Abdomen: Part I—The Abdominal Wall

and the lateral third of the inguinal ligament. It is inserted

the front of the symphysis pubis and from the pubic crest

The rectus abdominis muscle arises by two heads, from

from its fellow by the linea alba.

broader above and lies close to the midline, being separated

along the whole length of the anterior abdominal wall. It is

The rectus abdominis is a long strap muscle that extends

Rectus Abdominis

lumbar vertebrae by the lumbar fascia (Figs. 4.2 and 4.9).

nal oblique and the transversus muscles are attached to the

muscle is free, whereas the posterior borders of the inter

Note that the posterior border of the external oblique

to the pubic crest and the pectineal line (see Figs. 4.7 and 4.8).

internal oblique to form the conjoint tendon, which is fixed

pubis. The lowest tendinous fibers join similar fibers from the

into the xiphoid process, the linea alba, and the symphysis

(Figs.

rted into the 5th, 6th, and 7th

4.6 and 4.10). It is inse

the umbilicus, and one halfway between these two (see

one at the level of the xiphoid process, one at the level of

tendinous intersections:

segments by three transverse

The rectus abdominis muscle is divided into distinct

the ninth costal cartilage to the pubic tubercle.

(Figs. 4.3, 4.11, and 4.12). This extends from the tip of

naris

linea semilu

be palpated and often seen and is termed the

it contracts, its lateral margin forms a curved ridge that can

costal cartilages and the xiphoid process (see Fig. 4.3). When

Fig. 4.3). These intersections are strongly attached to the

present) and contains the anterior rami of the lower six

the rectus abdominis muscle and pyramidalis muscle (if

The rectus sheath is a long fibrous sheath that encloses

Rectus Sheath

of the rectus abdominis.

the linea alba (see Fig. 4.3). It lies in front of the lower part

from the anterior surface of the pubis and is inserted into

The pyramidalis muscle is often absent. It arises by its base

versus, which form the rectus sheath.

roses of the external oblique, internal oblique, and trans

The rectus abdominis is enclosed between the aponeu

(see below).

rectus sheath

anterior wall of the

-
-

Pyramidalis

posterior cutaneous nerves

sacrospinalis

T7–12

peritoneal

branch

posterior ramus

quadratus lumborum

lateral

cutaneous

nerve

lateral

cutaneous

nerve

anterior cutaneous nerve

external oblique

psoas

internal oblique

transversus

rectus muscles

FIGURE 4.9

ves.

Cross section of the abdomen showing the courses of the lower thoracic and first lumbar ner

Basic Anatomy

121

thoracic nerves and the superior and inferior epigastric ves

rior superior iliac spine, the aponeurosis of the internal

Between the costal margin and the level of the ante

and 7th costal cartilages and the intercostal spaces.

wall is formed by the thoracic wall—that is, the 5th, 6th

the aponeurosis of the external oblique. The posterior

Above the costal margin, the anterior wall is formed by

three levels (Fig. 4.13).

For ease of description, the rectus sheath is considered at

4.3, and 4.10).

roses of the three lateral abdominal muscles (see Figs. 4.2,

sels and lymph vessels. It is formed mainly by the aponeu

-
-

■

arcuate line

superficial

linea alba

transversus muscle

inferior

epigastric artery

conjoint tendon

fascia

transversalis

arcuate line

rectus muscle

external oblique

aponeurosis

tendinous

intersections

fascia

skin

xiphoid process

anterior layer of

internal oblique aponeurosis

posterior layer of

spermatic cord

internal oblique aponeurosis

transversus aponeurosis

fascia transversalis

extraperitoneal fat

inferior epigastric artery

peritoneum

pubis

FIGURE 4.10

Rectus sheath in anterior view

the rectus sheath.

Note the arrangement of the aponeuroses forming

and in sagittal section

(A)

(B).

tendinous

intersections

of rectus abdominis

umbilicus

iliac crest

anterior superior

iliac spine

inguinal canal

symphysis pubis

crease overlying

inguinal ligament

rectus abdominis

external oblique

linea semilunaris

costal margin

xiphoid process

xiphisternal joint

FIGURE 4.11

Anterior abdominal wall of a 27-year-old man.

122

CHAPTeR 4

anterior superior iliac spine, the posterior wall has a free,

posterior wall pass in front of the rectus at the level of the

It should be noted that where the aponeuroses forming the

muscle lies in contact with the fascia transversalis.

anterior wall. The posterior wall is absent, and the rectus

the pubis, the aponeuroses of all three muscles form the

Between the level of the anterosuperior iliac spine and

the transversus aponeurosis is directed behind the muscle.

oblique aponeurosis is directed in front of the muscle, and

oblique splits to enclose the rectus muscle; the external

The Abdomen: Part I—The Abdominal Wall

■

xiphisternal junction

xiphoid process

infrasternal angle

costal margin

median groove

tubercle of crest

anterior superior
iliac spine

right vertical line

scrotum

pubic
tubercle

superficial inguinal ring

linea
semilunaris

intertubercular
plane

subcostal
plane

transpyloric
plane

tip of ninth
costal cartilage

right

upper

quadrant

right

lower

quadrant

right
iliac

left iliac

left lower
quadrant

umbilical
region

left upper
quadrant

epigastrium

hypogastrium

FIGURE 4.12

Surface landmarks and regions of the anterior abdominal wall.

skin

rectus muscle

xiphoid process

intercostal muscles

aponeurosis of

external oblique

pectoralis major muscle

superficial fascia

rectus muscle

linea alba

extraperitoneal fat

peritoneum

fascia transversalis

transversus

internal oblique

external oblique

internal oblique

transversus

fascia transversalis

FIGURE 4.13

Transverse sections of the rectus sheath seen at three levels.

Below the level of the anterior superior iliac spine and above the pubis.

margin and the level of the anterior superior iliac spine.

Between the costal

Above the costal margin.

Basic Anatomy

Figs. 4.3 and 4.10).

attached to it by the muscle’s tendinous intersections (see

to the rectus abdominis muscle. The anterior wall is firmly

The posterior wall of the rectus sheath is not attached

pubis.

below the umbilicus to be attached to the symphysis

two sides. Wider above the umbilicus, it narrows down

the fusion of the aponeuroses of the lateral muscles of the

process down to the symphysis pubis and is formed by

Figs. 4.3, 4.7, and 4.13). This extends from the xiphoid

(see

linea alba

opposite side by a fibrous band called the

The rectus sheath is separated from its fellow on the

superior epigastric vessels.

the rectus sheath and pass upward to anastomose with the

and 4.10). At this site, the inferior epigastric vessels enter

(see Figs. 4.3

arcuate line

curved lower border called the

123

The symptoms that follow the trauma include midline abdomi

side below the level of the umbilicus. The source of the bleed

Hematoma of the Rectus Sheath

Hematoma of the rectus sheath is uncommon but important,

since it is often overlooked. It occurs most often on the right

ing is the inferior epigastric vein or, more rarely, the inferior

epigastric artery. These vessels may be stretched during a

severe bout of coughing or in the later months of pregnancy,

which may predispose to the condition. The cause is usually

blunt trauma to the abdominal wall, such as a fall or a kick.

nal pain. An acutely tender mass confined to one rectus

sheath is diagnostic.

C L I N I C A L N O T E S

transversus muscle

internal oblique

muscle

rectus muscle

external oblique

muscle

FIGURE 4.14

Action of the muscles of the anterior and

lateral abdominal walls. Arrows indicate line of pull of

different muscles.

xiphoid process

iliohypogastric
nerve

ilioinguinal nerve

inferior epigastric artery

position of deep
inguinal ring

deep

circumflex

iliac artery

lumbar
arteries

intercostal
arteries

superior epigastric artery

T10

T11

T12

lateral margin
of rectus
sheath

FIGURE 4.15

Segmental innervation of the anterior abdomi

A summary of the muscles of the anterior abdominal

pyramidalis is supplied by the 12th thoracic nerve.

by the lower six thoracic nerves (Figs. 4.9 and 4.15). The

and ilioinguinal nerves (L1). The rectus muscle is supplied

plied by the lower six thoracic nerves and the iliohypogastric

The oblique and transversus abdominis muscles are sup

Nerve Supply of Anterior Abdominal Wall

help in micturition, defecation, vomiting, and parturition.

larynx closed, they increase the intra-abdominal pressure and

simultaneously with the diaphragm, with the glottis of the

porting and protecting the abdominal viscera. By contracting

ribs and sternum. Their tone plays an important part in sup

occurs during coughing and sneezing by pulling down the

The muscles assist in the act of forced expiration that

accommodated.

diaphragm descends so that the abdominal viscera can be

assist the diaphragm during inspiration by relaxing as the

The muscles of the anterior and lateral abdominal walls

during the process.

the pelvis, and the pyramidalis keeps the linea alba taut

4.14). The rectus abdominis flexes the trunk and stabilizes

The oblique muscles laterally flex and rotate the trunk (Fig.

Function of the Anterior Abdominal Wall Muscles

wall

nal wall

(left) and arterial supply to the anterior abdominal

(right).

Muscles

wall, their nerve supply, and their action is given in Table 4.1.

iliaca that covers the iliacus muscle (see page 460).

limbs is formed from the fascia transversalis and the fascia

The femoral sheath for the femoral vessels in the lower

(see Fig. 4.10).

a similar layer lining the diaphragm and the iliacus muscle

the transversus abdominis muscle and is continuous with

The fascia transversalis is a thin layer of fascia that lines

Fascia Transversalis

Table 4.1

124

CHAPTeR 4

transversalis and the parietal peritoneum (see Fig. 4.10).

contains a variable amount of fat and lies between the fascia

The extraperitoneal fat is a thin layer of connective tissue that

Extraperitoneal Fat

The Abdomen: Part I—The Abdominal Wall

sive accumulation of fat in the fatty layer of the superficial

tone of its muscles. A middle-aged woman with poor abdomi

chest expands, the anterior abdominal wall also moves for

Normally,

Abdominal Muscles, Abdominothoracic Rhythm,

and Visceroptosis

The abdominal muscles contract and relax with respiration,

and the abdominal wall conforms to the volume of the abdomi-

nal viscera. There is an abdominothoracic rhythm.

during inspiration, when the sternum moves forward and the

ward. If, when the chest expands, the anterior abdominal wall

remains stationary or contracts inward, it is highly probable

that the parietal peritoneum is inflamed and has caused a

reflex contraction of the abdominal muscles.

The shape of the anterior abdominal wall depends on the

nal muscles who has had multiple pregnancies is often inca-

pable of supporting her abdominal viscera. The lower part of

the anterior abdominal wall protrudes forward, a condition

known as visceroptosis. This should not be confused with an

abdominal tumor such as an ovarian cyst or with the exces-

fascia.

C L I N I C A L N O T E S

Parietal Peritoneum

the inguinal ligament and symphysis pubis.

through the ring. They end by supplying the skin just above

inguinal ring, and by the ilioinguinal nerve, which emerges

the external oblique aponeurosis above the superficial

is represented by the iliohypogastric nerve, which pierces

not enter the rectus sheath (see Figs. 4.9, 4.15, and 4.16). It

The 1st lumbar nerve has a similar course, but it does

and supplying the skin.

They terminate by piercing the anterior wall of the sheath

supply the rectus muscle and the pyramidalis (T12 only).

nerves pierce the posterior wall of the rectus sheath to

intercostal muscles; see page 41). The lower six thoracic

spaces between the internal intercostal and the innermost

intercostal nerves, which run forward in the intercostal

cles, and the parietal peritoneum. (Compare with the

supply the skin of the anterior abdominal wall, the mus

ilioinguinal nerves, branches of the lumbar plexus. They

lumbar nerve is represented by the iliohypogastric and

intercostal nerves and the subcostal nerves, and the 1st

versus muscles. The thoracic nerves are the lower five

the interval between the internal oblique and the trans

nerves (Figs. 4.9, 4.15, and 4.16). They pass forward in

rior rami of the lower six thoracic and the 1st lumbar

The nerves of the anterior abdominal wall are the ante

Nerves of the Anterior Abdominal Wall

pelvis (see pages 278 and 296).

continuous below with the parietal peritoneum lining the

neum (see Fig. 4.10). This is a thin serous membrane and is

The walls of the abdomen are lined with parietal perito-

Muscles of the Anterior Abdominal Wall

T A B L E 4 . 1

Name of Muscle Origin

Insertion

Nerve Supply

Action

external oblique

Lower eight ribs

Xiphoid process, linea

alba, pubic crest,

pubic tubercle, iliac

crest

Lower six thoracic nerves

and iliohypogastric and

ilioinguinal nerves (L1)

Supports abdominal contents;

compresses abdominal

contents; assists in flex-

ing and rotation of trunk;

assists in forced expiration,

micturition, defecation,

parturition, and vomiting

Internal oblique

Lumbar fascia, iliac crest,

lateral two thirds of

inguinal ligament

Lower three ribs and

costal cartilages,

xiphoid process,

linea alba,

symphysis pubis

Tenses the linea alba

Transversus

Lower six thoracic nerves

and iliohypogastric and

ilioinguinal nerves (L1)

As above

Lower six costal carti-

lages, lumbar fascia,

iliac crest, lateral third

of inguinal ligament

Xiphoid process, linea

alba, symphysis

pubis

Lower six thoracic nerves

and iliohypogastric and

ilioinguinal nerves (L1)

Compresses abdominal

contents

Rectus

abdominis

Symphysis pubis and

pubic crest

5th, 6th and 7th costal

cartilages and

xiphoid process

Lower six thoracic nerves

Compresses abdominal con-

tents and flexes vertebral

column; accessory muscle

of expiration

Pyramidalis

(if present)

Anterior surface of pubis

Linea alba

12th thoracic nerve

Basic Anatomy

125

anterior branch of

seventh thoracic

nerve

lateral branch of

seventh thoracic

nerve

rectus

abdominis

muscle

lateral branch of

10th thoracic nerve

lateral branch

of iliohypogastric

nerve (L1)

superficial

inguinal ring

ilioinguinal
nerve

T10

T12

T11

FIGURE 4.16

Dermatomes and distribution of cutaneous

nerves on the anterior abdominal wall.

Abdominal Pain

pain in the overlying skin that may radiate down into the abdo

A pleurisy involving the lower costal parietal pleura causes

table, to rest the arms by the sides and draw up the knees to

muscles of the anterior abdominal wall of a patient are rigid

See also page 224.
Muscle Rigidity and Referred Pain
Sometimes, it is difficult for a physician to decide whether the

because of underlying inflammation of the parietal peritoneum

or whether the patient is voluntarily contracting the muscles

because he or she resents being examined or because the

physician’s hand is cold. This problem is usually easily solved

by asking the patient, who is lying supine on the examination

flex the hip joints. It is practically impossible for a patient to keep

the abdominal musculature tensed when the thighs are flexed.

Needless to say, the examiner’s hand should be warm.

men. Although it is unlikely to cause rigidity of the abdominal

muscles, it may cause confusion in making a diagnosis unless

these anatomic facts are remembered.

It is useful to remember the following:

Dermatomes over:

■

The xiphoid process: T7

■

The umbilicus: T10

■

The pubis: L1

Anterior Abdominal Nerve Block

Area of Anesthesia
The area of anesthesia is the skin of the anterior abdominal wall.

The nerves of the anterior and lateral abdominal walls are the

anterior rami of the 7th through the 12th thoracic nerves and the

1st lumbar nerve (ilioinguinal and iliohypogastric nerves).

Indications
An anterior abdominal nerve block is performed to repair

lacerations of the anterior abdominal wall.

gastric nerve passes forward around the abdominal wall and

and emerges through the superficial inguinal ring. The iliohypo

along the lower border of the costal margin and then infiltrating

(Fig. 4.16). An abdominal field block is most easily carried out

Procedure
The anterior ends of intercostal nerves T7 through T11 enter

the abdominal wall by passing posterior to the costal cartilages

the nerves as they emerge between the xiphoid process and the

10th or 11th rib along the costal margin.

The ilioinguinal nerve passes forward in the inguinal canal

pierces the external oblique aponeurosis above the superficial

inguinal ring. The two nerves are easily blocked by inserting the

anesthetic needle 1 in. (2.5 cm) above the anterior superior iliac

spine on the spinoumbilical line (see Fig. 4.17).

C L I N I C A L N O T E S

The dermatome of T7 is located in the epigastrium over

into the axillary vein via the lateral thoracic vein and, below,

the umbilicus (see Fig. 4.18). Above, the network is drained

The superficial veins form a network that radiates out from

Superficial Veins

Veins of the Anterior Abdominal Wall

wall (see Fig. 4.15).

muscle layers and supply the lateral part of the abdominal

branches of the abdominal aorta, pass forward between the

the descending thoracic aorta, and the four lumbar arteries,

The lower two posterior intercostal arteries, branches of

supplies the lower lateral part of the abdominal wall.

rior iliac spine and then continues along the iliac crest. It

4.15). It runs upward and laterally toward the anterosupe

nal iliac artery just above the inguinal ligament (see Fig.

The deep circumflex iliac artery is a branch of the exter

anastomoses with the superior epigastric artery.

the lower central part of the anterior abdominal wall, and

Fig. 4.10). It ascends behind the rectus muscle, supplying

lis to enter the rectus sheath anterior to the arcuate line (see

(see Figs. 4.4, 4.8, and 4.15). It pierces the fascia transversa

and medially along the medial side of the deep inguinal ring

iliac artery just above the inguinal ligament. It runs upward

The inferior epigastric artery is a branch of the external

nal wall, and anastomoses with the inferior epigastric artery.

cle, supplying the upper central part of the anterior abdomi

diaphragm (see Fig. 4.15). It descends behind the rectus mus

rectus sheath between the sternal and costal origins of the

of the internal thoracic artery, enters the upper part of the

one of the terminal branches

superior epigastric artery,

The

Arteries of the Anterior Abdominal Wall

abdominal wall, see Figure 4.16.

the symphysis pubis. For the dermatomes of the anterior

and that of L1 lies just above the inguinal ligament and

the xiphoid process, that of T10 includes the umbilicus,

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-

126

CHAPTeR 4

into the femoral vein via the superficial epigastric and great

The Abdomen: Part I—The Abdominal Wall

saphenous veins. A few small veins, the

an important portal–systemic venous anastomosis.

along the ligamentum teres to the portal vein. This forms

connect the network through the umbilicus and

veins,

paraumbilical

iliohypogastric nerve

genitofemoral nerve

ilioinguinal nerve

pubic tubercle

costal margin

anterior superior

iliac spine

anterior superior
iliac spine

pubic tubercle

T10

FIGURE 4.17

ks. T7

Anterior abdominal wall nerve bloc

to the pubic tubercle and infiltrating the subcutaneous tis

blocked by inserting the needle through the skin just lateral

(X). The terminal branches of the genitofemoral nerve are

blocked by inserting the needle about 1 in. (2.5 cm) above

the costal margin. The iliohypogastric ilioinguinal nerves are

though T11 are blocked (X) as they emerge from beneath

the anterior superior iliac spine on the spinoumbilical line

sue with anesthetic solution (X).

lateral thoracic vein

portal vein in porta hepatis

lumbar veins

superficial epigastric vein

paraumbilical veins

varicosed vein

FIGURE 4.18

Superficial veins of the anterior abdominal

epigastric vein. This occurs if either the superior or the

between the lateral thoracic vein and the superficial

is obstructed. On the

the direction taken by venous blood when the portal vein

Arrows

and the portal vein via paraumbilical veins.

are anastomoses between systemic veins

left

wall. On the

indicate

right is an enlarged anastomosis

interior vena cava is obstructed.

ses with the superficial epigastric vein, a tributary of the great

If the superior or inferior vena cava is obstructed, the venous

Caval Obstruction

blood causes distention of the veins running from the anterior

chest wall to the thigh. The lateral thoracic vein anastomo-

saphenous vein of the leg. In these circumstances, a tortuous

varicose vein may extend from the axilla to the lower abdomen

(see Fig. 4.18).

C L I N I C A L N O T E S

Deep Veins

bar veins drain into the inferior vena cava.

intercostal veins drain into the azygos veins, and the lum

internal thoracic and external iliac veins. The posterior

follow the arteries of the same name and drain into the

gastric, inferior epigastric, and deep circumflex iliac veins,

The deep veins of the abdominal wall, the superior epi-

Portal Vein Obstruction

In cases of portal vein obstruction (see Fig. 4.19), the super-

ficial veins around the umbilicus and the paraumbilical veins

become grossly distended. The distended subcutaneous veins

radiate out from the umbilicus, producing in severe cases the

clinical picture referred to as caput medusae.

C L I N I C A L N O T E S

Basic Anatomy

ward to the superficial inguinal nodes (see Fig. 4.19).

the axilla; below the level of the iliac crests, it drains down

axillary group of nodes, palpated on the posterior wall of

level of the iliac crests is drained upward to the posterior

(Fig. 4.19). The lymph of the skin of the back above the

downward and laterally to the superficial inguinal nodes

muscle. Below the level of the umbilicus, the lymph drains

pated just beneath the lower border of the pectoralis major

rior axillary (pectoral) group of nodes, which can be pal

wall above the level of the umbilicus is upward to the ante

The lymph drainage of the skin of the anterior abdominal

Superficial Lymph Vessels

Lymph Drainage of the Anterior Abdominal Wall

127

-
-

inguinal node) caused by an infection or malignant tumor of

group of lymph nodes is clinically important. For example, it is

Skin and its Regional Lymph Nodes

Knowledge of the areas of the skin that drain into a particular

possible to find a swelling in the groin (enlarged superficial

the skin of the lower part of the anterior abdominal wall or that

of the buttock.

C L I N I C A L N O T E S

Deep Lymph Vessels

part of the posterior wall, namely, the deep inguinal ring.

therefore strongest where it lies opposite the weakest

inguinal ligament (see Figs. 4.3 and 4.8). This wall is

laterally by the origin of the internal oblique from the

External oblique aponeurosis, reinforced

Anterior wall.

Walls of the Inguinal Canal

external spermatic fascia.

give attachment to the

crura,

4.3, 4.5, and 4.8). The margins of the ring, sometimes called

immediately above and medial to the pubic tubercle (see Figs.

in the aponeurosis of the external oblique muscle and lies

is a triangular-shaped defect

superficial inguinal ring

The

the internal covering of the round ligament of the uterus).

(or

internal spermatic fascia

ring give attachment to the

upward from the external iliac vessels. The margins of the

it medially are the inferior epigastric vessels, which pass

and the symphysis pubis (see Figs. 4.4 and 4.8). Related to

ligament midway between the anterior superior iliac spine

transversalis, lies about 0.5 in. (1.3 cm) above the inguinal

* an oval opening in the fascia

deep inguinal ring,

The

Later, as the result of growth, the deep ring moves laterally.

ficial ring so that the canal is considerably shorter at this age.

child, the deep ring lies almost directly posterior to the super

immediately above the inguinal ligament. In the newborn

oblique muscle (see Figs. 4.3 and 4.8). It lies parallel to and

ficial inguinal ring, a hole in the aponeurosis of the external

versalis (see page 137), downward and medially to the super

extends from the deep inguinal ring, a hole in the fascia trans

The canal is about 1.5 in. (4 cm) long in the adult and

from the uterus to the labium majus.

females, it allows the round ligament of the uterus to pass

structures to pass to and from the testis to the abdomen. In

part of the anterior abdominal wall. In the males, it allows

The inguinal canal is an oblique passage through the lower

and para-aortic (lumbar) nodes.

the internal thoracic, external iliac, posterior mediastinal,

The deep lymph vessels follow the arteries and drain into

Inguinal Canal

-
-

the

caput medusae

anterior axillary lymph nodes

superficial inguinal nodes

posterior axillary lymph nodes

FIGURE 4.19

Lymph drainage of the skin of the anterior and posterior abdominal walls. Also shown is an example of caput

medusae in a case of portal obstruction caused by cirrhosis of the liver.

openings for the fingers when the glove is viewed from the outside.

with the openings for the fingers seen inside a glove with the absence of

edges of the rings cannot be observed externally. Compare this arrangement

fascia is attached to the margins of the superficial inguinal ring so that the

attached to the margins of the deep inguinal ring and the external spermatic

rings as openings. One must remember that the internal spermatic fascia is

*A common frustration for medical students is the inability to observe these