ANTERIOR ABDOMINAL WALL

The abdomen is the region of the body that is located between the diaphragm above and the pelvic inlet below.

It is divided into nine quadrants, by:

Two vertical lines at the level of: Midclavicular point superiorly Midinguinal point inferiorly

Two horizontal lines at the level of: Subcostal edges superiorly Right and left iliac tubercles inferiorly

The structures of the abdominal wall from out side to inside.1. Skin.2. Superficial fascia.3. Deep fascia4. Muscles.5. Extraperitoneal fascia6. Parietal peritoneum.

SKIN

Skin is loosely attached to the underlining structures except the umbilicus.

The umbilicus is a scar representing the site of attachment of the umbilical cord in the fetus; it is situated in the linea alba.

SUPERFICIAL FASCIA

The superficial fascia is divided into: Superficial fatty layer (fascia of Camper) Deep membranous layer (Scarpa's fascia)

SUPERFICIAL FATTY LAYER (CAMPER’S FASCIA).

It’s continuous with superficial fat over the rest of the body.

In the scrotum is modified as a thin smooth muscular layer called dartos muscle.

Deep membranous layer.(Scarpa’s fascia).

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.

DEEP FASCIA

Is a thin layer of connective tissue covering the muscles, it lies immediately deep to the membranous layer of superficial fascia.

MUSCLESThe 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 The internal oblique The 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.

ORIGIN

Lower eight ribs(5-12)

INSERTIONNERVE SUPPLY

lower six thoracic nerves

(T7-T12)iliohypogastric and ilioinguinal

nerves (L1)

ACTION

Supports abdominal contents; compresses abdominal contentsassists in flexing and rotation of trunkassists in forced expiration, micturition, defecation, parturition, and vomiting

Xiphoid processlinea alba

pubic crest pubic tubercle

iliac crest

EXTERNAL OBLIQUE MUSCLEBroad, thin, muscular sheet.

There is a triangular-shaped defect in the external oblique aponeurosis that lies immediately above and medial to the pubic tubercle known as 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

ORIGIN

Lumbar fascia,iliac crest, lateral two thirds of the inguinal ligament.

INSERTIONNERVE SUPPLY

lower six thoracic nerves

(T7-T12)iliohypogastric and ilioinguinal

nerves (L1)

ACTION

Supports abdominal contents; compresses abdominal contentsassists in flexing and rotation of trunkassists inforced expiration, micturition, defecation, parturition, and vomiting

lower three ribs and their costal cartilagesxiphoid process. linea alba. symphysis pubis.

INTERNAL OBLIQUE MUSCLEThe internal oblique muscle is also a broad, thin, muscular sheet that lies deep to the external oblique

Lower fibres of internal oblique are joinedby similar fibers from the transversusto form the conjoint tendon .

As the spermatic cord (or round ligament of the uterus) passes under the lower border of theinternal oblique, it carries with it some of the muscle fibers that are called thecremaster muscle .

TRANSVERSUS MUSCLEThin sheet of muscle that lies deep to the internal oblique

ORIGIN

Lower six costal cartilagesLumbar fascia,iliac crest, lateral two thirds of the inguinal ligament.

INSERTION

NERVE SUPPLY

lower six thoracic nerves

(T7-T12)iliohypogastric and ilioinguinal

nerves (L1)

ACTION

compresses abdominal contents

xiphoid process.linea alba. Symphysis pubis.

RECTUS ABDOMINISThe 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.

ORIGIN

symphysis pubispubic crest.

INSERTIONNERVE SUPPLY

lower six thoracic nerves

(T7-T12)

ACTION

compresses abdominal contents; flexes vertebral column; accessory muscle of expiration

fifth, sixth, and seventh costal cartilages xiphoid process

RECTUS ABDOMINIS

When it contracts, its lateral margin forms a curved ridge that can be palpated and often seen and is termed the linea semilunaris, this extends from the tip of the ninth costal cartilage to the pubic tubercle.

The rectus abdominis muscle is divided into distinct segments by three transverse tendinous intersections at the level of: xiphoid process. umbilicus. halfway between these two.

PYRAMIDALIS

ORIGIN

anterior surface of the pubis.

INSERTIONNERVE SUPPLY

Twelvth thoracic nerveT12

ACTION

Tenses the linea alba

Linea alba

EXTRAPERITONEAL FASCIAThe extraperitoneal fat is a thin layer of connective tissue that contains a variable amount of fat and lies between the fascia transversalis and the parietal peritoneum

PARIETAL PERITONEUMThe walls of the abdomen are lined with parietal peritoneum. This is a thin serous membrane and is continuous below with the parietal peritoneum lining the pelvis.

NERVE SUPPLY

The nerves of the anterior abdominal wall are the anterior rami of the lower six thoracic and the first lumbar nerves.

The thoracic nerves are the lower five intercostal nerves and the subcostal nerves First lumbar nerve is represented by the iliohypogastric and ilioinguinal nerves, branches of the lumbar

plexus

They supply the skin of the anterior abdominal wall, the muscles, and the parietal peritoneum. The lower six thoracic nerves pierce the posterior wall of the rectus sheath to supply the rectus muscle

and the pyramidalis (T12 only).

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.

Dermatomes of the abdominal wall. The xiphoid process: T7 The umbilicus: T10 The pubis: L1

BLOOD SUPPLY

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 arteries Lumbar arteries Deep circumflex iliac arteries

The superior epigastric artery, one of the terminal branches of the internal thoracic artery, enters the upper part of the rectus sheath It descends behind the rectus muscle, supplying the upper central part of the anterior abdominal wall, and anastomoses with the inferior epigastric artery.

The inferior epigastric artery is a branch of the external iliac artery just above the inguinal ligament. the rectus muscle, supplying the lower central part of the anterior abdominal wall, and anastomoses with the superior epigastric artery.

The deep circumflex iliac artery is a branch of the external iliac artery just above the inguinal ligament.

It supplies the lower lateral part of the abdominal wall.

The lower two posterior intercostal arteries, branches of the descending thoracic aorta, and the four lumbar arteries, branches of the abdominal aorta, pass forward between the muscle layers and supply the lateral part of the abdominal wall

VENOUS DRAINAGE

SUPERFICIAL VEINS The superficial veins form a network that radiates out from the umbilicus. Above, the network is drained into the axillary vein via the lateral thoracic vein. Below, into the femoral vein via the superficial epigastric and great saphenous veins.

DEEP VEINS The deep veins of the abdominal wall, the superior epigastric, inferior epigastric, and deep circumflex iliac

veins, follow the arteries of the same name and drain into the internal thoracic and external iliac veins.

superficial Lymphatics in the region above the umbilicus

Drain into the axillary lymph nodes which can be palpated just beneath the lower border of the pectoralis major muscle

Lymphatics in the region below the umbilicusDrain into the superficial inguinal nodes

The deep lymph vessels follow the arteries and drain into the internal thoracic, external iliac, posterior mediastinal, and para-aortic (lumbar) nodes.