Anterior Abdominal Wall

Enumerate the layers of anterior abdominal wall.

Layers of anterior abdominal wall are:

• Skin
• Superficial fascia
• Outer fatty layer (Camper’s fascia)
• Inner membranous layer (Scarpa’s fascia)
• Muscles (arranged in three layers)
  • External oblique
  • Internal oblique
  • Transversus abdominis
• Fascia transversalis
• Extraperitoneal tissue
• Peritoneum (parietal layer)

There is no deep fascia in the anterior abdominal wall.

Name the planes used for dividing abdominal cavity into regions. 

Abdomen is divided into nine regions using:

• Two horizontal planes:
  • Transpyloric plane: passes in front through the tips of the ninth costal cartilages and behind at the lower border of L1 vertebra.
  • Subcostal plane: passes in front at the level of inferior margin of 10^th rib and behind through the upper part of L3 vertebra.
• Two vertical planes:
  • Right and left midclavicular planes: pass through the midpoint of clavicle to the midinguinal point (midway between the anterior superior iliac spine and pubic symphysis.

What are the vertebral levels of important abdominal planes?

• Transpyloric plane: Lower border of L1 vertebra
• Subcostal plane: Upper part of body of L3 vertebra
• Plane passing through the highest point of iliac crest: L4 Vertebra
• Intertubercular plane – Upper part of body of L5 vertebra

Enumerate the structures present at the transpyloric plane.

• Pylorus of stomach
• Neck of pancreas
• Duodeno – jejunal flexure
• Fundus of gall bladder
• Hilum of kidneys
• Origin of superior mesenteric artery
• Tip of ninth costal cartilage
• Termination of spinal cord

Name the nine abdominal regions and their main contents. 

Write the origin, insertion and nerve supply of muscles of anterior abdominal wall.

 What are the action/s of anterior abdominal wall muscles?

Anterior abdominal wall muscles

• Support and protect the abdominal viscera.
• Help in forced expiration that occurs during coughing, sneezing, vomiting,
• Increase the intra-abdominal pressure and thereby help in defecation, micturition (urination), and parturition (childbirth).
• Rotate the trunk to the opposite side (external oblique of one side and internal oblique of the opposite side).
• Flex the trunk laterally (external and internal oblique muscles of the same side).
• Flex the trunk anteriorly (rectus abdominis). 

What are linea alba, linea semilunaris?

Linea alba  

• Is an avascular fibro-tendinous raphe formed by the interlacing fibers of the aponeurosis of the three lateral muscles of anterior abdominal wall (external oblique, internal oblique and transversus abdominis).  
• It extends from the xiphoid process to pubic symphysis.

Linea semilunaris

• A curved fibrous line at the lateral margin of the rectus sheath that extends from the  tip of the ninth costal cartilage to the pubic tubercle.

 Write a short note on Umbilicus.

• Is a depressed scar in the midline of anterior abdominal wall , normally between the xhiphoid process and pubic symphysis or between L3 and L4 vertebra.
• Represents the site of attachment of fetal end of umbilical cord.
• Is innervated by T10 spinal segment.
• Acts as a water – shed line with respect to lymph and venous flow.
• Is one of the sites of portocaval anastomosis.
• Fibrous bands attached to the inner aspect of umbilicus:
• Ligamentum teres hepatis – remnant of left umbilical vein
• Median umbilical ligament (Urachus)– remnant of allantois
• Medial umbilical ligaments – remnant of umbilical arteries

Applied Aspect

Describe the superficial fascia of anterior abdominal wall.

Superficial fascia of anterior abdominal wall: In the lower part of the anterior abdominal wall (below the line passing through the midpoint between the umbilicus and pubic symphysis), the superficial fascia has two layers:

• Superficial fatty layer (Camper’s fascia)
• Deep membranous layer (Scarpa’s fascia)

        The superficial fatty layer is continuous with the superficial fascia of the rest of the body, the membranous layer is devoid of fat and has more of elastic fibers.

Attachment of Scarpa’s fascia:

• From the lower half of anterior abdominal wall, it passes over the inguinal ligament and is attached to the deep fascia of the thigh along an horizontal line (Holden’s line approx. 8cm.) passing laterally from the pubic tubercle.
• Medially it passes downwards over the body of the pubis and becomes continuous with the superficial perineal fascia (Colle’s fascia). The superficial perineal fascia is attached laterally to conjoint ischiopubic rami and posteriorly it is fused with the posterior border of perineal membrane.
• It also extends into the penis and scrotum (labia majora in females).

Applied Aspect

 Enumerate the arteries that supply anterior abdominal wall.

The following arteries supply anterior abdominal wall:

• Superior epigastric, branch of internal thoracic artery.
• Lateral cutaneous branches of posterior intercostal arteries.
• Superficial epigastric , branch of femoral artery
• Inferior epigastric – branch of external iliac artery.
• Deep circumfles, branch of external iliac artery.

Enumerate the cutaneous nerves innervating anterior abdominal wall.

Following cutaneous nerves supply anterior abdominal wall:

• Anterior cutaneous branches of T7-T11 intercostal nerves and subcosatl nerve.
• Lateral cutaneous branches of T10 and T11 intercostal nerves.
• Iliohypogastric nerve.

 Describe in brief the lymphatic drainage of anterior abdominal wall.

• Lymphatics from anterior abdominal wall  above the level of umbilicus drains into axillary lymph nodes.
• Lymphatics from anterior abdominal wall  below the level of umbilicus drains into superficial inguinal lymph nodes.