Anterior Abdominal Wall

• The anterior abdominal wall is defined as the region of the trunk that lies between the diaphragm above and the inlet of the pelvis below.
• The anterior abdominal wall is formed above by the lower part of the thoracic cage and below by muscles (rectus abdominis, external oblique, internal oblique & transverse abdominis) and fasciae.
• The posterior abdominal wall is formed in the midline by the lumbar spine and laterally - by the 12th rib, and the muscles (psoas major & quadratus lumborum).
• The liver and gallbladder are in the right upper quadrant of the abdominal cavity.
• The stomach and spleen are in the left upper quadrant of the abdominal cavity.
• The cecum and appendix are in the right lower quadrant of the abdominal cavity.
• The end of the descending colon and sigmoid colon are in the left lower quadrant of the abdominal cavity.
• Pain arising out of the foregut derived structures is referred to the epigastric region.
• Pain arising out of the midgut derived structures is referred to the umbilical region.
• Spigelian hernia - The neck of the sac is usually narrow so that adhesion and strangulation of its contents are common complications.
• Femoral hernias pass below the inguinal ligament and inguinal hernias pass above.
• Direct inguinal hernias are rare in women, and most are bilateral.
• 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.
• The hernia is usually small and starts off as a small protrusion of extraperitoneal fat between the fibers of the linea alba.
• Spigelian hernia (semilunar) occurs through the aponeurosis of the transverses abdominis just lateral to the lateral edge of the rectus sheath.
• The hernial sac does not protrude through the umbilical scar, but through the linea alba in the region of the umbilicus.
• Direct inguinal hernia composes about 15% of all inguinal hernias.
• 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.
• Epigastric hernia occurs through the widest part of the linea alba, anywhere between the xiphoid process and the umbilicus.
• During a direct inguinal hernia, the abdominal contents will protrude through the weak area of the posterior wall of the inguinal canal medial to the inferior epigastric vessels in the inguinal Hesselbach's triangle and after that through superficial inguinal ring.
• A femoral hernia (i.e. a loop of the small intestine) may protrude through the femoral ring and after then through a saphenous opening in the deep fascia of the thigh and bulge upwards under the skin of the abdominal wall.
• Pain arising out of the hindgut derived structures is referred to the hypogastric region.
• The skin, superficial fascia, deep fascia, muscles, transversalis fascia, extraperitoneal fat, and parietal peritoneum are layers of the anterior abdominal wall.
• The muscles of the anterior-lateral abdominal wall are the rectus abdominis, external oblique, internal oblique, and transverse abdominis.
• Above the arcuate line, the anterior wall of the rectus sheath is 1.5 mm thick, composed of the aponeuroses of the external and internal oblique, and the posterior wall is 1.5 mm thick, composed of the aponeuroses of the internal oblique and transverse.
• In females, the genital branch is accompanied by the round ligament of the uterus and supplies sensation to the labia majora.
• Superficial veins drain into the axillary vein via the Lateral thoracic vein and below into the femoral vein via the Superficial epigastric and great saphenous veins.
• Paraumbilical veins connect the network through the umbilicus and along the ligamentum teres in falciform ligament to the portal vein.
• The superficial inguinal ring is a triangular-shaped opening in the aponeurosis of the external oblique muscle and lies immediately above and lateral to the pubic tubercle.
• The inguinal canal transmits the Ilioinguinal nerve (L1) in both sexes.
• Below the arcuate line, the anterior wall of the rectus sheath is 3.0 mm thick, composed of the aponeuroses of the external oblique, internal oblique and transverse, and the posterior wall is 0 mm thick, composed of transverse fascia.
• The cutaneous lymph vessels above the level of the umbilicus drain upward into the anterior axillary lymph nodes.
• In males, the genital branch (L1 - L2) of the genitofemoral nerve supplies the scrotal skin and cremaster muscle.
• Deep arteries lie in the neurovascular plane: Superior epigastric, Posterior intercostals arteries, Lumbar arteries, Deep circumflex iliac artery, and Inferior epigastric.
• The vessels below umbilicus drain downward into the superficial inguinal nodes.
• The inguinal canal allows the spermatic cord (structures to pass to and from the testis) in males and permits the passage of the round ligament of the uterus in females.
• Superficial arteries that supply skin are: Superficial epigastric and Superficial circumflex iliac.
• All nerves and deep blood vessels lie in the neurovascular plane: between internal oblique and transverse muscles.
• Deep veins follow arteries.