INNERVATION OF ANTERIOR ABDOMINAL WALL
The somatic innervation of anterior abdominal wall is from thoracoabdominal nerves (T7-L1).These includes anterior rami of lower thoracic nerves which are continuation of intercostal nerves and run in transversus abdominis plane and ilioinguinal, iliohypogastric nerves from first lumbar nerve. Each of the thoraco abdominal nerve gives off branch as posterior, lateral and anterior cutaneous branch to supply the skin of abdomen and back. Lateral cutaneous nerve supplies lateral abdominal wall after passing through TAP and terminal branches pierces the rectus sheath and rectus muscle to continue as anterior cutaneous nerves. Aberrant nerves may arise from lateral aspect of linea semilunaris and may cause block sparing. Ilioinguinal and iliohypogastric(L1) may also receive contributions from T12 and L2-L3. These nerve passes through anterior inferior abdominal wall into the TAP and have indistinct course which explains patchy block.