PHSI 208 Lecture 2: GI2
Document Summary
Know the general structural and regulatory features of the gi tract. Know the cellular and electrical basis for gi motility. There are 6 functions: secretion, digestion, absorption, motility, excretion, and host defense. Commensal bacteria contributes to the digestion of food (ex: dietary fibre by fermentation). It provides essential nutrients such as secondary and deconjugated bile acids. It is friendly bacteria that inhabits the large intestine. Immune cells allow commensal bacteria, but kill harmful bacteria. Primary bile acids are reabsorbed by commensal bacteria at the distal part of the small intestine. The large intestine then converts it to secondary/deconjugated bile acids that difuse across the membrane. Cb also prevents pathogenic microorganisms from colonizing the intestine. (ex: c. difficile, v. cholerae, salmonella and listeria). Some bacteria can puncture through the epithelium and can also produce toxins, which leads to secretion of fluids, massive loss of fluids, severe dehydration, and even death.
