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Lecture 41
Small Intestine-Large Intestine
Term | Definition |
---|---|
Small Intestine | primary site of digestion and reab |
Structure | duodenum,jejunum,ileum.many folds inc surface area 600 fold. 91/day (may be 1/day) presented. (2 food,7 secretions). 1-2/day to colon,200 mL in feces |
Villi | folds of SI wall tissue.crypts of lieberkuhn at base.cells migrate upward-die by digestion.cells replaced every 3 days. |
Microvilli | brush border.folds of cell-membrane at the tips of villi cells. |
Mucus | protection from digestive enzyme |
Motility | Basic electrical rhythm (BER)-higher at duodenum than at ileum.moves chyme down SI-peristaltic waves of longitudinal smooth muscle segmentation:mixing contractions of circular smooth muscle |
Malabsorption | dec amino acid absorb leads to wasting (dec muscle mass) dec card and fat absrob. leads to inc stool and gas,dec vitamin absorb.autoimmune (chrons) and allergic diseases |
Diarrhea | mult causes-most common SI motify>absorp.loss of h2o and k+:potentially serious or fatal neural/heart problems.dehydration leads to shock.travel-change in water/electrolytes kills LI bacteria or e coli/other bacteria in food |
Large Intestine-Colon | handles absorption of h2o and na+ and some k+. no nutrient absorp from SI-some from bacteria |
Structure | SI leads to secum leads to ascending,descending colons leads to rectum leads to anus.internal and external sphincters control anus.appendix-closed pouch of lymphoid tissues off cecum |
Gastroileal Reflex | food in stomach cause relaxation of cecum and allows ileum to empty.gastrin releases ileocecal valve |
Absorption | active transport of na+,water follows |
Feces/Fiber | feces is minerals,fiber,bacteria,h2o.bacteria grow even during starvation.fiber is cellulose and related compounds.fiber inc colonic activity,dec colon |
Bacteria | e coli and other types-appear soon after birth.bacteria acquire nutrients from the colon mucosa.may produce useful vitamins and essential amino acids.can invade body after radiation poisoning |
Defecation | gastric triggers colonic contraction leads to mass movement into rectum inc pressure. inc rectal pressure causes reflex relaxation of internal anal sphincter (smooth muscle).voluntary control of external anal sphincter (skeletal muscle) |
Constipation | defecation varies from 3/day to 1 per 3 days. no sig health,consequences except discomfort.no "poison" absorption. |
Flatus | most is bacteria-some from ingestion.mult gases-smell is due to sulfides.sound:gas forced through closed sphincter.basal flatal rate:15mL/hr. 1 passage?hr.post prandial flatal rate:176mL/hr after 1 helping of baked beans-inc frequency. |