Peritoneal Innervation

Expansion

• Parietal peritoneum - supplied by the segmental somatic nerves of the overlying body wall (intercostal, subcostal, lumbar and phrenic). Sensitive to touch, pressure, temperature and cutting. Pain is sharp and well localised
• Visceral peritoneum - supplied by autonomic afferents. Sensitive only to stretch and ischaemia, not cutting. Pain is dull, poorly localised and midline

This explains the classic history of appendicitis: early periumbilical visceral pain (midgut, T10), then migration to sharp right iliac fossa pain once the parietal peritoneum is inflamed.

Two further points follow. The central diaphragmatic peritoneum is supplied by the phrenic nerve, so blood or pus under the diaphragm refers pain to the shoulder tip (C4). And in the pelvis, much of the peritoneum lies out of contact with the body wall, which is why pelvic appendicitis and pelvic abscesses produce surprisingly few abdominal signs.