Answer to Question #312739 in Human Anatomy and Physiology for Sonia

Question

1. Identify the enzymes secreted by the pancreas. Describe the concept of zymogens.
2. Discuss the sequential digestion of proteins, by gastric pepsin, pancreatic enzymes and duodenal enteropeptidase at the apical membrane of the small intestine.
3. Explain membrane transport mechanisms for amino acids and dipeptides by intestinal epithelial cells.
4. Describe the sequence of events in the colon and anal sphincter occurring during reflective defecation differentiating those movements under voluntary control and those under autonomic control

Answer 1

1.Trypsinogen and chymotrypsinogen, zymogens secreted by the pancreas, are activated in the intestinal tract to trypsin and chymotrypsin.

2.Luminal digestion of dietary proteins begins in the stomach and is initiated by pepsin that is secreted by chief cells, deep in the mucosal crypts.

3.There is virtually no absorption of peptides longer than four amino acids. However, there is abundant absorption of di- and tripeptides in the small intestine. These small peptides are absorbed into the small intestinal epithelial cell by cotransport with H+ ions via a transporter called PepT1.

4.The defecation reflex occurs when the internal anal sphincter relaxes and the external anal sphincter contracts. The rectoanal inhibitory reflex (RAIR) is an involuntary internal anal sphincter relaxation in response to rectal distention. After the defecation reflex is triggered, you can either delay or defecate