Muhammad Sohaib Shahid
(Lecturer & Course Co-ordinator MIT)
University Institute of Radiological
Sciences & Medical Imaging
Technology (UIRSMIT)
Abdominal Wall
• The abdomen is the region of the trunk that lies
between the diaphragm above and the inlet of the
pelvis below.
• Structure of the Anterior Abdominal Wall
The anterior abdominal wall is made up of skin,
superficial fascia, deep fascia, muscles, extra
peritoneal fascia, and parietal peritoneum.
Skin
• The skin is loosely attached to the underlying
structures except at the umbilicus, where it is
tethered to the scar tissue. The natural lines of
cleavage in the skin are constant and run
downward and forward almost horizontally
around the trunk. The umbilicus is a scar
representing the site of attachment of the
umbilical cord in the fetus; it is situated in the
linea alba
Clinical Notes
• Surgical Incisions
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 a narrow
scar, whereas one that crosses the lines will heal as
wide or heaped-up scars.
• Infection of the Umbilicus
In the adult, the umbilicus often receives scant
attention in the shower and is consequently a
common site of infection.
Nerve Supply
• The cutaneous nerve supply to the anterior
abdominal wall is derived from the anterior rami
of the lower six thoracic and the first lumbar
nerves .
• The first lumbar nerve is represented by the
iliohypogastric and the ilioinguinal nerves.
Dermatomes
• The dermatome of T7 is located in the
epigastrium over the xiphoid process.
• The dermatome of T10 includes the umbilicus
• L1 lies just above the inguinal ligament and the
symphysis pubis.
Blood Supply
• Arteries
The skin near the midline is supplied by branches
of the superior and the inferior epigastric
arteries.
• The skin of the flanks is supplied by branches of
the intercostal, the lumbar, and the deep
circumflex iliac arteries .
• In addition, the skin in the inguinal region is
supplied by the superficial epigastric, the
superficial circumflex iliac, and the
superficial external pudendal arteries,
branches of the femoral artery.
Veins
The venous drainage passes above mainly into
the axillary vein via the lateral thoracic vein
and below into the femoral vein via the
superficial epigastric and the great saphenous
veins
Superficial Fascia
• The superficial fascia is divided into a superficial fatty layer (fascia of
Camper) and a deep membranous layer (Scarpa's fascia) . The fatty
layer is continuous with the superficial fat over the rest of the body and
may be extremely thick (3 in. [8 cm] or more in obese patients).
• The membranous layer is thin and fades out laterally and above
where it becomes continuous with the superficial fascia of the back and
the thorax, respectively.
• Inferiorly, the membranous layer passes onto the front of the thigh,
where it fuses with the deep fascia one fingerbreadth below the inguinal
ligament.
• In the midline inferiorly, the membranous layer of fascia is not attached
to the pubis but forms a tubular sheath for the penis (or clitoris).
• Below in the perineum, it enters the wall of the scrotum (or labia
majora). From there it passes to be attached on each side to the
margins of the pubic arch; it is here referred to as Colles' fascia.
• In the scrotum, the fatty layer of the superficial
fascia is represented as a thin layer of smooth
muscle, the dartos muscle. The membranous layer
of the superficial fascia persists as a separate layer.
• Deep Fascia
The deep fascia in the anterior abdominal wall is
merely a thin layer of connective tissue covering
the muscles; it lies immediately deep to the
membranous layer of superficial fascia.
Membranous Layer of Superficial Fascia 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
superficial perineal pouch via the penis and scrotum.
Rupture of the penile urethra may be followed by
extravasations 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 .
• When closing abdominal wounds it is usual for a surgeon to
put in a continuous suture uniting the divided membranous
layer of superficial fascia. This strengthens the healing
wound, prevents stretching of the skin scar, and makes for a
more cosmetically acceptable result.
Muscles of the Anterior Abdominal
Wall
• The muscles of the anterior abdominal wall consist of three
broad thin sheets that are aponeurotic in front; from
exterior to interior they are the :
• External oblique, Internal oblique, and Transversus.
• On either side of the midline anteriorly is, in addition, a
wide vertical muscle, the rectus abdominis . As the
aponeuroses of the three sheets pass forward, they enclose
the rectus abdominis to form the rectus sheath.
• The lower part of the rectus sheath might contain a small
muscle called the pyramidalis.
External Oblique
• The external oblique muscle is a broad, thin, muscular
sheet that arises from the outer surfaces of the lower
eight ribs and fans out to be inserted into the
xiphoid process, the linea alba, the pubic crest,
the pubic tubercle, and the anterior half of the
iliac crest .
• A triangular-shaped defect in the external oblique
aponeurosis lies immediately above and medial to the
pubic tubercle. This is known as the superficial
inguinal ring. The spermatic cord (or round
ligament of the uterus) passes through this opening
and carries the external spermatic fascia (or the
external covering of the round ligament of the uterus)
from
the
margins
of
the
ring.
• Between the anterior superior iliac spine and the
pubic tubercle, the lower border of the aponeurosis is
folded backward on itself, forming the inguinal
ligament .
• From the medial end of the ligament, the lacunar
ligament extends backward and upward to the
pectineal line on the superior ramus of the pubis . Its
sharp, free crescentic edge forms the medial margin
of the femoral ring.
• On reaching the pectineal line, the lacunar ligament
becomes continuous with a thickening of the
periosteum called the pectineal ligament
• The lateral part of the posterior edge of the inguinal
ligament gives origin to part of the internal oblique
and transversus abdominis muscles. To the inferior
rounded border of the inguinal ligament is attached
the deep fascia of the thigh, the fascia lata.
Internal Oblique
• The internal oblique muscle is also a broad, thin, muscular sheet that
lies deep to the external oblique; most of its fibers run at right angles
to those of the external oblique .
• It arises from the lumbar fascia, the anterior two thirds of the
iliac crest, and the lateral two thirds of the inguinal ligament.
The muscle fibers radiate as they pass upward and forward.
• The muscle is inserted into the lower borders of the lower three ribs
and their costal cartilages, the xiphoid process, the linea alba,
and the symphysis pubis.
• The internal oblique has a lower free border that arches over the
spermatic cord (or round ligament of the uterus) and then descends
behind it to be attached to the pubic crest and the pectineal line.
Near their insertion, the lowest tendinous fibers are joined by similar
fibers from the transversus abdominis to form the conjoint tendon .
The conjoint tendon is attached medially to the linea alba, but it has a
lateral free border.
• As the spermatic cord (or round ligament of the uterus) passes under
the lower border of the internal oblique, it carries with it some of the
muscle fibers that are called the cremaster muscle . The cremasteric
fascia is the term used to describe the cremaster muscle and its fascia.
Transversus
• The transversus muscle is a thin sheet of muscle
that lies deep to the internal oblique, and its fibers
run horizontally forward .
• It arises from the deep surface of the lower six
costal cartilages, the lumbar fascia, the
anterior two thirds of the iliac crest, and the
lateral third of the inguinal ligament.
• It is inserted into the xiphoid process, the linea
alba, and the symphysis pubis. The lowest
tendinous fibers join similar fibers from the
internal oblique to form the conjoint tendon,
which is fixed to the pubic crest and the
pectineal line .
Rectus Abdominis
• The rectus abdominis is a long strap muscle that
extends along the whole length of the anterior
abdominal wall. It is broader above and lies close to the
midline, being separated from its fellow by the linea
alba.
• The rectus abdominis muscle arises by two heads,
from the front of the symphysis pubis and from the
pubic crest . It is inserted into the fifth, sixth, and
seventh costal cartilages and the xiphoid
process .
• The rectus abdominis muscle is divided into distinct
segments by
three
transverse
tendinous
intersections: one at the level of the xiphoid process,
one at the level of the umbilicus, and one halfway
between these two . These intersections are strongly
attached to the anterior wall of the rectus sheath .
• The rectus abdominis is enclosed between the
aponeuroses of the external oblique, internal
oblique, and transversus, which form the rectus
sheath.
• Note that the posterior border of the external
oblique muscle is free, whereas the posterior
borders of the internal oblique and transversus
muscles are attached to the lumbar vertebrae by the
lumbar fascia
Pyramidalis Muscle
• The pyramidalis muscle is often absent. It arises by
its base from the anterior surface of the pubis and
is inserted into the linea alba . It lies in front of the
lower part of the rectus abdominis.
Function of the Anterior Abdominal Wall
Muscles
• The oblique muscles laterally flex and rotate the trunk. The
rectus abdominis flexes the trunk and stabilizes the pelvis,
and the pyramidalis keeps the linea alba taut during the
process.
• The muscles of the anterior and lateral abdominal walls
assist the diaphragm during inspiration by relaxing as the
diaphragm descends so that the abdominal viscera can be
accommodated.
• The muscles assist in the act of forced expiration that
occurs during coughing and sneezing by pulling down the
ribs and sternum. Their tone plays an important part in
supporting and protecting the abdominal viscera. By
contracting simultaneously with the diaphragm, with the
glottis of the larynx closed, they increase the intraabdominal pressure and help in micturition, defecation,
vomiting, and parturition.
Nerve Supply of Anterior Abdominal Wall
Muscles
• The oblique and transversus abdominis muscles
are supplied by the lower six thoracic nerves and
the iliohypogastric and ilioinguinal nerves (L1).
The rectus muscle is supplied by the lower six
thoracic nerves . The pyramidalis is supplied by the
12th thoracic nerve.
Inguinal Canal
• The inguinal canal is an oblique passage through the
lower part of the anterior abdominal wall.
• In the males, it allows structures to pass to and from the
testis to the abdomen.
• In females it allows the round ligament of the uterus to
pass from the uterus to the labium majus.
• The canal is about 1.5 in. (4 cm) long in the adult and
extends from the deep inguinal ring, a hole in the
fascia transversalis , downward and medially to the
superficial inguinal ring, a hole in the aponeurosis of the
external oblique muscle.
• It lies parallel to and immediately above the inguinal
ligament. In the newborn child, the deep ring lies almost
directly posterior to the superficial ring so that the canal
is considerably shorter at this age. Later, as the result of
growth, the deep ring moves laterally.
• The deep inguinal ring, an oval opening in the
fascia transversalis, lies about 0.5 in. (1.3 cm) above
the inguinal ligament midway between the anterior
superior iliac spine and the symphysis pubis .
Related to it medially are the inferior epigastric
vessels, which pass upward from the external iliac
vessels. The margins of the ring give attachment to
the internal spermatic fascia (or the internal
covering of the round ligament of the uterus).
• The superficial inguinal ring is a triangularshaped defect in the aponeurosis of the external
oblique muscle and lies immediately above and
medial to the pubic tubercle . The margins of the
ring, sometimes called the crura, give attachment to
the external spermatic fascia.
Walls of the Inguinal Canal
• Anterior wall: External oblique aponeurosis,
reinforced laterally by the origin of the internal oblique
from the inguinal ligament . This wall is therefore
strongest where it lies opposite the weakest part of the
posterior wall, namely, the deep inguinal ring.
• Posterior wall: Conjoint tendon medially, fascia
transversalis laterally . This wall is therefore strongest
where it lies opposite the weakest part of the anterior
wall, namely, the superficial inguinal ring.
• Roof or superior wall: Arching lowest fibers of the
internal oblique and transversus abdominis muscles
• Floor or inferior wall: Upturned lower edge of the
inguinal ligament and, at its medial end, the lacunar
ligament .
Function of the Inguinal Canal
• The inguinal canal allows structures of the
spermatic cord to pass to and from the testis to
the
abdomen
in
the
male.
(Normal
spermatogenesis takes place only if the testis
leaves the abdominal cavity to enter a cooler
environment in the scrotum.)
• In the female, the smaller canal permits the
passage of the round ligament of the uterus from
the uterus to the labium majus.
Mechanics of the Inguinal Canal
• The inguinal canal in the lower part of the anterior abdominal wall is a
site of potential weakness in both sexes. It is interesting to consider how
the design of this canal attempts to lessen this weakness.
• Except in the newborn infant, the canal is an oblique passage with the
weakest areas, namely, the superficial and deep rings, lying some
distance apart.
• The anterior wall of the canal is reinforced by the fibers of the internal
oblique muscle immediately in front of the deep ring.
• The posterior wall of the canal is reinforced by the strong conjoint
tendon immediately behind the superficial ring.
• On coughing and straining, as in micturition, defecation, and
parturition, the arching lowest fibers of the internal oblique and
transversus abdominis muscles contract, flattening out the arched roof
so that it is lowered toward the floor. The roof may actually compress
the contents of the canal against the floor so that the canal is virtually
closed .
• When great straining efforts may be necessary, as in defecation and
parturition, the person naturally tends to assume the squatting position;
the hip joints are flexed, and the anterior surfaces of the thighs are
brought up against the anterior abdominal wall. By this means, the
lower part of the anterior abdominal wall is protected by the thighs
Spermatic Cord
• The spermatic cord is a collection of structures that pass
through the inguinal canal to and from the testis . It begins
at the deep inguinal ring lateral to the inferior epigastric
artery and ends at the testis.
• Structures of the Spermatic Cord
• The structures are as follows:
• Vas deferens
• Testicular artery
• Testicular veins (pampiniform plexus)
• Testicular lymph vessels
• Autonomic nerves
• Remains of the processus vaginalis
• Genital branch of the genitofemoral nerve, which supplies
the cremaster muscle
Coverings of the Spermatic Cord (the Spermatic Fasciae)
• The coverings of the spermatic cord are three
concentric layers of fascia derived from the layers of the
anterior abdominal wall. Each covering is acquired as
the processus vaginalis descends into the scrotum
through the layers of the abdominal wall .
• External spermatic fascia derived from the external
oblique aponeurosis and attached to the margins of the
superficial inguinal ring
• Cremasteric fascia derived from the internal oblique
muscle
• Internal spermatic fascia derived from the fascia
transversalis and attached to the margins of the deep
inguinal ring
• Vasectomy
• Bilateral vasectomy is a simple operation
performed to produce infertility. Under local
anesthesia, a small incision is made in the upper
part of the scrotal wall, and the vas deferens is
divided between ligatures. Spermatozoa may be
present in the first few postoperative
ejaculations, but that is simply an emptying
process. Now only the secretions of the seminal
vesicles and prostate constitute the seminal
fluid, which can be ejaculated as before.
Scrotum
• The scrotum is an outpouching of the lower part of the anterior
abdominal wall. It contains the testes, the epididymides, and the
lower ends of the spermatic cords .The wall of the scrotum has the
following layers:
• Skin: The skin of the scrotum is thin, wrinkled, and pigmented and
forms a single pouch. A slightly raised ridge in the midline indicates the
line of fusion of the two lateral labioscrotal swellings. (In the female,
the swellings remain separate and form the labia majora.)
• Superficial fascia: This is continuous with the fatty and membranous
layers of the anterior abdominal wall; the fat is, however, replaced by
smooth muscle called the dartos muscle. This is innervated by
sympathetic nerve fibers and is responsible for the wrinkling of the
overlying skin. The membranous layer of the superficial fascia (often
referred to as Colles' fascia) is continuous in front with the
membranous layer of the anterior abdominal wall (Scarpa's fascia), and
behind it is attached to the perineal body and the posterior edge of the
perineal membrane . At the sides it is attached to the ischiopubic rami.
Both layers of superficial fascia contribute to a median partition that
crosses the scrotum and separates the testes from each other.
• Spermatic fasciae: These three layers lie beneath the
superficial fascia and are derived from the three layers of
the anterior abdominal wall on each side, as previously
explained.
• The external spermatic fascia is derived from the
aponeurosis of the external oblique muscle.
• The cremasteric fascia is derived from the internal oblique
muscle
• The internal spermatic fascia is derived from the fascia
transversalis.
• The cremaster muscle is supplied by the genital branch
of the genitofemoral nerve . The cremaster muscle can be
made to contract by stroking the skin on the medial aspect
of the thigh. This is called the Cremasteric reflex.
• The function of the cremaster muscle is to raise the testis
and the scrotum upward for warmth and for protection
against injury. For testicular temperature and fertility.
Structure of the Posterior Abdominal Wall
• The posterior abdominal wall is formed in the midline by the five lumbar
vertebrae and their intervertebral discs and laterally by the 12th ribs, the upper
part of the bony pelvis , the psoas muscles, the quadratus lumborum muscles,
and the aponeuroses of origin of the transversus abdominis muscles. The
iliacus muscles lie in the upper part of the bony pelvis.
• Lumbar Vertebrae
• The body of each vertebra is massive and kidney shaped, and it has to bear the
greater part of the body weight. The fifth lumbar vertebra articulates with the
base of the sacrum at the lumbosacral joint.
• The intervertebral discs in the lumbar region are thicker than in other regions
of the vertebral column. They are wedge shaped and are responsible for the
normal posterior concavity in the curvature of the vertebral column in the
lumbar region (lordosis). For a full description of the structure of the lumbar
vertebrae and the intervertebral discs.
• Twelfth Pair of Ribs
It should be noted that the head of the 12th rib has a single facet for
articulation with the body of the 12th thoracic vertebra. The anterior end is
pointed and has a small costal cartilage, which is embedded in the musculature
of the anterior abdominal wall. In many people it is so short that it fails to
protrude beyond the lateral border of the erector spinae muscle on the back.
Muscles of the Posterior Abdominal Wall
• Psoas Major
• The Psoas muscle arises from the roots of the transverse
processes, the sides of the vertebral bodies, and the
intervertebral discs, from the 12th thoracic to the 5th
lumbar vertebrae . The fibers run downward and laterally
and leave the abdomen to enter the thigh by passing
behind the inguinal ligament. The muscle is inserted into
the lesser trochanter of the femur. The psoas is enclosed
in a fibrous sheath that is derived from the lumbar fascia.
The sheath is thickened above to form the medial arcuate
ligament.
• Nerve supply: This muscle is supplied by the lumbar
plexus.
• Action: The psoas flexes the thigh at the hip joint on the
trunk, or if the thigh is fixed, it flexes the trunk on the
thigh, as in sitting up from a lying position.
Quadratus Lumborum
• The quadratus lumborum is a flat, quadrilateral-shaped
muscle that lies alongside the vertebral column. It arises below
from the iliolumbar ligament, the adjoining part of the iliac
crest, and the tips of the transverse processes of the lower
lumbar vertebrae . The fibers run upward and medially and are
inserted into the lower border of the 12th rib and the
transverse processes of the upper four lumbar vertebrae. The
anterior surface of the muscle is covered by lumbar fascia,
which is thickened above to form the lateral arcuate ligament
and below to form the iliolumbar ligament.
• Nerve supply: This muscle is supplied by the lumbar plexus.
• Action: It fixes or depresses the 12th rib during respiration
and laterally flexes the vertebral column to the same side.
• Iliacus
• The Iliacus muscle is fan shaped and arises from
the upper part of the iliac fossa. Its fibers join
the lateral side of the psoas tendon to be inserted
into the lesser trochanter of the femur. The
combined muscles are often referred to as the
iliopsoas.
• Nerve supply: This muscle is supplied by the
femoral nerve, a branch of the lumbar plexus.
• Action: The iliopsoas flexes the thigh on the
trunk at the hip joint, or if the thigh is fixed, it
flexes the trunk on the thigh.
Peritoneal Lining of the Abdominal Walls
• The walls of the abdomen are lined with parietal
peritoneum. This is a thin serous membrane
consisting of a layer of mesothelium resting on
connective tissue. It is continuous below with the
parietal peritoneum lining the pelvis
• Nerve Supply
• The central part of the diaphragmatic peritoneum
is supplied by the phrenic nerves, and the
peripheral part is supplied by the lower intercostal
nerves. The peritoneum lining the anterior and
posterior abdominal walls is supplied segmentally
by intercostal and lumbar nerves, which also
supply the overlying muscles and skin.
Paracentesis of the Abdomen
• Paracentesis of the abdomen may be necessary
to withdraw excessive collections of peritoneal
fluid, as in ascites secondary to cirrhosis of the
liver or malignant ascites secondary to advanced
ovarian cancer. Under a local anesthetic, a
needle or catheter is inserted through the
anterior abdominal wall. The underlying coils of
intestine are not damaged because they are
mobile and are pushed away by the cannula.
McBurney's Incision
• This is chiefly used for cecostomy and appendectomy.
It gives a limited exposure only, and should any doubt
arise about the diagnosis, an infraumbilical right
paramedian incision should be used instead.
• An oblique skin incision is made in the right iliac
region about 2 in. (5 cm) above and medial to the
anterior superior iliac spine. The external and internal
oblique and transversus muscles are incised or split in
the line of their fibers and retracted to expose the
fascia transversalis and the peritoneum. The latter are
now incised and the abdominal cavity is opened. The
incision is closed in layers, with no postoperative
weakness.
Abdominal Herniae
• A hernia is the protrusion of part of the abdominal
contents beyond the normal confines of the abdominal
wall .
• It consists of three parts:
• the sac, the contents of the sac, and the coverings of
the sac.
• The hernial sac is a pouch (diverticulum) of
peritoneum and has a neck and a body.
• The hernial contents may consist of any structure
found within the abdominal cavity and may vary from
a small piece of omentum to a large viscus such as the
kidney.
• The hernial coverings are formed from the layers of
the abdominal wall through which the hernial sac
passes.
Femoral Hernia
• The hernial sac descends through the femoral canal
within the femoral sheath, creating a femoral hernia.
The femoral sheath, is a protrusion of the fascial
envelope lining the abdominal walls and surrounds the
femoral vessels and lymphatics for about 1 in. (2.5 cm)
below the inguinal ligament .
• The femoral artery, as it enters the thigh below the
inguinal ligament, occupies the lateral compartment of
the sheath. The femoral vein, which lies on its medial
side and is separated from it by a fibrous septum,
occupies the intermediate compartment. The lymph
vessels, which are separated from the vein by a fibrous
septum, occupy the most medial compartment.
• A femoral hernia is more common in women than in
men (possibly because of a wider pelvis and femoral
canal)
Umbilical Herniae
• Congenital umbilical hernia, or exomphalos (omphalocele), is
caused by a failure of part of the midgut to return to the
abdominal cavity from the extraembryonic coelom during fetal
life. The hernial sac and its relationship to the umbilical cord .
• Acquired infantile umbilical hernia is a small hernia that
sometimes occurs in children and is caused by a weakness in the
scar of the umbilicus in the linea alba . Most become smaller and
disappear without treatment as the abdominal cavity enlarges.
• Acquired umbilical hernia of adults is more correctly referred
to as a paraumbilical hernia. The hernial sac does not protrude
through the umbilical scar, but through the linea alba in the region
of the umbilicus . Paraumbilical herniae gradually increase in size
and hang downward. The neck of the sac may be narrow, but the
body of the sac often contains coils of small and large intestine and
omentum. Paraumbilical herniae are much more common in
women than in men.
Lumbar Hernia
• The lumbar hernia occurs through the lumbar
triangle and is rare. The lumbar triangle (Petit's
triangle) is a weak area in the posterior part of
the abdominal wall. It is bounded anteriorly by
the posterior margin of the external oblique
muscle, posteriorly by the anterior border of the
latissimus dorsi muscle, and inferiorly by the
iliac crest. The floor of the triangle is formed by
the internal oblique and the transversus
abdominis muscles. The neck of the hernia is
usually large, and the incidence of strangulation
low
Lumbar Triangle
Inguinal Hernia