BIOL 2420 Lecture Notes - Lecture 15: Internal Anal Sphincter, Ileocecal Valve, External Anal Sphincter

• School: University of Manitoba
• Department: Biological Sciences
• Course: BIOL 2420
• Professor: Diana Mlinar

Document Summary

Small surface area: no villi or convolutions, begins at the ileum as the ascending colon, the transverse colon, then the descending colon, after the descending colon it ends at the sigmoid colon. About 1500 ml of chyme enters the caecum each day: moves through the ileocaecal sphincter, due to contractions of the distal ileum. The ileocaecal valve closes because of colonic stretch: prevents feces from entering the small intestine. Haustral contractions are very slow: about 2 per hour, moves contents along the large intestine. Distension of the rectal walls triggers the defecation reflex. Increased peristaltic activity of the sigmoid colon: relaxation of the internal anal sphincter. Smooth muscle: pressure builds, voluntary relaxation of the external anal sphincter allows feces to exit the body. Over a 24 hour period the body undergoes two physiologically distinct nutritional states: absorptive state. Period when ingested nutrients absorbed from the digestive tract supply the energy needs of the body. Anabolic state: post - absorptive state.