This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Intestinal obstruction, Subject name: Surgery
First to recover from post-operative ileus: 
Select and explain. 
A. Small intestine, B. Stomach, C. Colon, D. None
A: Small intestine
Answer: A: Small intestine 
Explanation: POST-OPERATIVE ILEUS - Following most abdominal operations or injuries, the motility of GI tract is transiently impaired. - Proposed mechanisms responsible for this dysmotility are surgical stress-induced sympathetic reflexes, inflammatory response mediator release, and anesthetic / analgesic effects; each of which can inhibit intestinal motility. Return of normal motility: small intestineQ (within 24 hours) > Gastric (48 hours)Q>Colonic(3-5 days) Post-operative ileus is most pronounced in colon. - Because small bowel motility is returned before colonic and gastric motility, listening for bowel sounds is not a reliable indicator that ileus has fully resolved.