Abdominal Wall Anatomy

Ephraim McDowell performed the first successful laparotomy on December 25, 1809. The patient was Jane Todd Crawford, a distant cousin of Abraham Lincoln’s wife, Mary Todd Lincoln.

Abdominal Wall Layers

• Skin
• Subcutaneous tissue
  • Camper fascia (superficial adipose)
  • Scarpa fascia (fibrous connective tissue
• Superficial fascia
• External oblique muscle
  • Originate from lower 7 ribs
  • Most posterior insert into anterior half of iliac crest
  • Lower portion of aponeurosis that extends from ASIS to pubic tubercle is called inguinal (Poupart) ligament
  • Inguinal ligament is lower free edge of external oblique aponeurosis
    • Femoral hernia passes posterior to inguinal ligament
    • Inguinal hernia passes anterior and superior to inguinal ligament
• Internal oblique muscle
  • Originates from iliopsoas fascia beneath lateral half of inguinal ligament
  • Uppermost fibers insert into lower 5 ribs
  • Some muscle fascicles accompany the spermatic cord into the scrotum as cremasteric muscle
• Transversus abdominis muscle
  • Arises from lower six costal cartilages, spines of lumbar vertebrae, iliac crest, and iliopsoas fascia beneath lateral third of inguinal ligament
  • Form aponeurotic arch which lies superior to Hesselbach triangle
• Transversalis fascia
  • Makes up floor of Hesselbach triangle
    • Hesselbach triangle → site of direct inguinal hernia
      • Inguinal ligament
      • Lateral margin of rectus sheath
      • Inferior epigastric vessels
• Preperitoneal adipose and areolar tissue
  • Preperitoneal space is between transversalis fascia and parietal peritoneum
  • Includes the following structures
    • Inferior epigastric artery and vein
    • Medial umbilical ligaments
    • Median umbilical ligament
    • Falciform ligament of the liver 
• Peritoneum 

Vascular Supply

• Arterial supply
  • Last 6 intercostal arteries
  • Last 4 lumbar arteries
  • Superior epigastric arteries
    • Terminal branch of internal mammary
    • Reaches posterior surface of rectus abdominis and descends to anastomose with branches of inferior epigastric artery
  • Inferior epigastric arteries
    • Branches off of external iliac artery
    • Courses through preperitoneal areolar tissue to enter lateral rectus sheath at the semilunar line of Douglas
  • Deep circumflex iliac arteries
    • Arises from lateral aspect of external iliac artery near origin of inferior epigastric artery
    • Gives rise to ascending branch that penetrates abdominal wall musculature above iliac crest 
• Venous drainage
  • Superficial veins above the umbilicus → internal mammary → intercostal → long thoracic → SVC
  • Veins inferior to umbilicus (superficial epigastric, circumflex iliac, pudendal) → saphenous vein → IVC

Lymphatics

• Supraumbilical → axillary LN
• Infraumbilical → superficial inguinal LN
• Liver → umbilicus → anterior abdominal wall LN

Innervation

• Ilioinguinal nerve
  • Sensory to hypogastrium and lower abdominal wall
  • Courses with spermatic cord, emerges from external inguinal ring providing sensory innervation to skin of inguinal region and scrotum/labium
• Iliohypogastric nerve
  • Run parallel to 12th thoracic nerve
  • Pierce transversus abdominis near iliac crest
  • Sensory to hypogastrium and lower abdominal wall