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Anterior Abdominal Wall
Abdomen, Pelvis & Perineum Unit
Lecture 1
‫ حيدر جليل األعسم‬.‫د‬
Abdomen
It is the region of trunk that lies
between diaphragm above and
pelvic inlet below.
Circumferentially, it is bounded by
abdominal wall. The abdominal
wall is bordered as follows:
• Superiorly by xiphoid process
and costal margins.
• Posteriorly by vertebral column.
• Inferiorly by upper parts of the
pelvic bones.
Anterior Abdominal Wall
Abdominal wall is divided into Anterior and Posterior walls.
Structure of Anterior Abdominal Wall:
1. Skin
2. Superficial fascia
3. Deep fascia
4. Muscles
5. Extraperitoneal fascia
6. Parietal peritoneum
Skin
Skin is loosely attached to the
underlying structures except at
the umbilicus (tethered to scar
tissue).
The natural lines of cleavage in
the skin are constant and run
almost horizontally around the
trunk. The umbilicus is a scar
representing the site of
attachment of umbilical cord in
the fetus; it is situated in the
linea alba
Superficial Fascia – fatty layer
It is divided into an outer fatty layer (Camper’s fascia) and a deep
membranous layer (Scarpa's fascia).
Camper's fascia contains fat and is
continuous with superficial fat over
the rest of the body.
In men’s scrotum, the fatty layer
of superficial fascia loses its fat
and represented as a thin
layer of smooth muscle
(dartos muscle).
In women, this superficial layer
retains some fat and is a
component of the labia majora.
Superficial Fascia – Membranous layer
Scarpa's fascia is thin membranous layer & has the following relations
Laterally, continuous with superficial fascia of the back.
Superiorly, continuous with superficial fascia of the thorax.
Inferiorly, fuses with the deep fascia of thigh (fascia lata) 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).
Superficial Fascia – Membranous layer
In the perineum, fuses with perineal superficial fascia (Colles'
fascia) and with perineal body and posterior margin of the
perineal membrane.
In men, it blends with fatty layer as they both pass over the
penis, forming the superficial fascia of the penis, before they
continue into the scrotum to form dartos fascia.
In women, it continues into labia majora and anterior part of the
perineum.
Deep Fascia of Anterior Abdominal
Wall
It is merely a thin layer of connective tissue covering
the muscles and lies immediately deep to the
membranous layer of superficial fascia
Muscles of Anterior Abdominal Wall
They consist of three broad thin sheets of muscles that are
aponeurotic in front (external oblique, internal oblique &
transversus abdominis). There is also a wide vertical muscle
(rectus abdominis)on
either side of the midline.
Muscles of Anterior Abdominal Wall
As aponeuroses of these three sheets pass forward,
they enclose rectus abdominis to form rectus sheath.
Lower part of rectus sheath may contain a small
muscle (pyramidalis)
External Oblique
Shape: broad, thin, muscular sheet.
Origin: from outer surfaces of lower eight ribs
Insertion: xiphoid process, linea alba, pubic crest, pubic tubercle, and
anterior half of the iliac crest.
A triangular-shaped defect in external oblique aponeurosis lies above
and medial to pubic tubercle known as superficial inguinal ring.
Between anterior superior iliac spine
and pubic tubercle, lower border of
the aponeurosis is folded backward on
itself, forming inguinal ligament.
From the medial end of the ligament,
lacunar ligament extends backward
and upward to pectineal line on the
superior ramus of the pubis.
Deep fascia of the thigh (fascia lata)
is attached to the inferior rounded
border of the inguinal ligament
Internal Oblique
Shape: broad, thin, muscular sheet.
Origin: lumbar fascia, anterior 2/3 of iliac crest, lateral 2/3 of inguinal
ligament.
Insertion: lower borders of lower three ribs (10th, 11th & 12th) & their costal
cartilages, xiphoid process, linea alba & symphysis pubis.
Its fibres run at right angles to external oblique fibres (upward and forward).
Internal Oblique
It has a lower free border that arches
over spermatic cord (or round
ligament of uterus) and attached to
pubic crest and pectineal line. The
lowest tendinous fibers are joined by
similar fibers from transversus
abdominis to form conjoint tendon
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 cremaster
muscle. The cremasteric fascia is the
term used to describe the cremaster
muscle and its fascia.
Transversus Abdominis
Shape: thin sheet of muscle.
Origin: from deep surface of lower six costal cartilages (interdigitating
with the diaphragm), lumbar fascia, anterior two thirds of iliac crest, and
lateral third of inguinal ligament.
Insertion: into xiphoid process, linea alba,
and symphysis pubis.
It lies deep to internal oblique, and its fibers
run horizontally forward.
The lowest tendinous fibers join similar fibers
from internal oblique to form conjoint tendon.
Posterior borders of internal oblique and
transversus muscles are attached
to lumbar spines by lumbar fascia.
Rectus Abdominis
Shape: long strap muscle extending along anterior abdominal wall.
Origin: by two heads, from the front of symphysis pubis and pubic crest.
Insertion: into 5th, 6th & 7th costal cartilages and xiphoid process.
When it contracts, its lateral margin forms a
curved ridge (linea semilunaris) that extends
from tip of 9th costal cartilage to pubic tubercle.
It is divided into distinct segments by three
transverse tendinous intersections:
one at the level of xiphoid process,
one at the level of umbilicus,
and one halfway between these two.
These intersections are attached to anterior
wall of rectus sheath only.
Rectus abdominis muscle is enclosed in
rectus sheath formed by aponerosus of other
Flat muscles.
Pyramidalis
It is often absent and arises by its base from anterior
surface of pubis and is inserted into linea alba. It lies
in front of lower part of the rectus abdominis muscle.
Rectus Sheath
It is long fibrous sheath that encloses rectus abdominis muscle and pyramidalis muscle.
It is formed mainly by aponeuroses of the three lateral abdominal muscles (External
Oblique, Internal Oblique & Transversus Abdominis.
Contents of rectus sheath: Rectus abdominis muscle, Pyramidalis muscle, anterior
rami of lower six thoracic nerves and superior and inferior epigastric vessels and lymph
vessels.
Rectus Sheath
Rectus sheath walls are formed of different components according to three levels.
Above costal margin, anterior wall is formed by aponeurosis of external oblique.
Posterior wall by thoracic wall (5th, 6th & 7th costal cartilages & intercostal spaces).
Between costal margin and level of anterior superior iliac spine, internal oblique
aponeurosis splits to enclose rectus muscle; external oblique aponeurosis is directed in
front of the muscle, and transversus aponeurosis is directed behind muscle.
Between the level of the anterosuperior iliac spine and the pubis, aponeuroses of all
three muscles form the anterior wall. The posterior wall is absent.
The posterior wall has a free, curved lower border called arcuate line; where inferior
epigastric vessels enter rectus sheath and anastomose with superior epigastric vessels.
Fascia Transversalis
It is a thin layer of fascia that lines transversus abdominis
muscle and is continuous with a similar layer lining the
diaphragm and the iliacus muscle. The femoral sheath for the
femoral vessels in the lower limbs is
formed from fascia transversalis
and fascia iliaca that covers
the iliacus muscle.
Extraperitoneal Fat
It is a thin layer of connective tissue that contains a
variable amount of fat and lies between fascia
transversalis and parietal peritoneum.
Nerve Supply of Abdominal Wall
1- Anterior rami of lower six thoracic (lower five intercostal & subcostal
nerves) pierce posterior wall of rectus sheath to supply rectus muscle &
pyramidalis (T12 only)
2- First lumbar nerves (iliohypogastric & ilioinguinal nerves). They do
not enter rectus sheath but iliohypogastric nerve pierces external
oblique aponeurosis and ilioinguinal nerve emerges through superficial
inguinal ring. They supply skin above inguinal lig. & symphysis pubis.
They all pass in an interval between
internal oblique and transversus muscles.
T7 Dermatome is located in the
epigastrium over xiphoid process.
T10 Dermatome includes the umbilicus
L1 Dermatome lies just above inguinal
ligament & symphysis pubis.
Blood Supply of Abdominal Wall
Arteries:
Skin near the midline: by superior & inferior epigastric arteries.
Skin of the flanks: by intercostal, lumbar & deep circumflex iliac arteries.
Skin in inguinal region is supplied by femoral artery (superficial
epigastric & superficial circumflex iliac arteries).
Veins:
Superficial Veins: they form a network
that radiates out from the umbilicus.
Above, they are drained into axillary vein
via lateral thoracic vein and, below, into
femoral vein via superficial epigastric
and great saphenous veins.
Deep Veins: Superior & Inferior epigastric,
and deep circumflex iliac veins (drain
into internal thoracic & external iliac veins.
Posterior intercostal veins drain into azygos
Lumbar veins drain into the inferior vena cava
Lymph Drainage of the Abdominal Wall
Superficial Lymph Vessels of Anterior abdominal wall:
Above the umbilicus: anterior axillary (pectoral) group of nodes.
Below the umbilicus: superficial
inguinal nodes.
Superficial Lymph Vessels of back:
Above the iliac crests: posterior
axillary group of nodes
Below the iliac crests: Superficial
inguinal nodes.
Deep Lymph Vessels
They follow the arteries and drain
into internal thoracic, external iliac,
posterior mediastinal & para-aortic
(lumbar) nodes.
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