Anterior abdominal wall — concise study notes

Layers (superficial → deep)

1. Skin
2. Superficial fascia (fatty and membranous layers)
3. Deep (investing) fascia over muscles
4. Muscles and their aponeuroses
5. Extraperitoneal (subserous) fascia
6. Parietal peritoneum

Muscles (anterior/lateral)

• External oblique, internal oblique, transversus abdominis, rectus abdominis, pyramidalis (small; T12).
• Muscles provide wall strength, form rectus sheath and inguinal region structures.

Nerve supply

• Cutaneous motor and sensory supply from the anterior rami of lower 6 thoracic nerves: lower 5 intercostals (T7–T11) and subcostal (T12).
• These nerves innervate skin, parietal peritoneum, and the anterior abdominal muscles.

Key dermatomes

• T7: epigastrium, over xiphoid process.
• T10: umbilicus (useful clinical landmark).
• L1: skin just above the inguinal ligament and over the pubic symphysis.

Arterial supply

• Midline/central supply:
• Superior epigastric artery (branch of internal thoracic)
• Inferior epigastric artery (branch of external iliac)
• Superficial epigastric artery (from femoral)
• Lateral thoracic artery (from axillary) supplies upper anterior skin laterally
• Flank/lateral supply:
• Posterior intercostal arteries (from thoracic aorta)
• Lumbar arteries (from abdominal aorta)
• Deep circumflex iliac artery (from external iliac)
• Superficial circumflex iliac artery (from femoral)

Venous drainage

• Superficial veins form a network radiating from the umbilicus.
• Drain superiorly toward the thoracic/axillary veins.
• Drain inferiorly toward the femoral vein via the superficial epigastric and great saphenous veins.
• Paraumbilical veins connect the superficial network and ligamentum teres to the portal vein, creating important portal–systemic anastomoses (clinical: caput medusae in portal hypertension).

Lymphatic drainage

• Superficial (cutaneous)
• Above the umbilicus → anterior axillary (pectoral) lymph nodes.
• Below the umbilicus → superficial inguinal lymph nodes.
• Deep lymphatics follow arteries and drain to:
• Internal thoracic nodes
• External iliac nodes
• Para-aortic (lumbar) nodes
• Posterior mediastinal nodes

Clinical correlations (brief)

• Dermatomes help localize visceral pain and incision placement (e.g., T10 for umbilicus).
• Portal–systemic anastomoses at the umbilicus cause visible abdominal wall veins in portal hypertension (caput medusae).
• Knowledge of epigastric vessels is essential to avoid bleeding in midline and lower abdominal incisions and hernia repairs.

High-yield summary

• The anterior abdominal wall consists of six layers from skin to parietal peritoneum; motor/sensory supply is from T7–T12 (and L1 sensory contribution), arterial supply is segmental with midline and lateral sources, venous drainage includes superficial networks connected to the portal system, and lymph drains differently above vs below the umbilicus.