PHSI 208 Lecture Notes - Lecture 53: Hepatic Portal System, Portal Triad, Lactose Intolerance
Document Summary
5. 5 l of food, fluid and secretions enter the small intestine, an additional 3. 5 l of hepatic, pancreatic and intestinal secretions are added: most secretions are added in the duodenum. A combination of segmental and peristaltic contractions mixes the chyme w/ enzymes and expose digested nutrients to mucosal epithelium for absorption (7. 5 l absorbed mainly in duodenum and jejunum) Motility regulated to ensure proper digestion and absorption. Parasympathetic innervation, gastrin and cholecystokinin promote motility. Villi increase surface area available for absorption and secrete mucus: mucus secreted by goblet cells, not mucus cells. Crypts contain hormone and fluid secretory cells + stem cells: stem cells to replace damaged enterocytes. Most nutrients are absorbed into capillaries in the villi. Fats enter lacteals of lymphatics (as they are too large for the capillaries) Enterocytes have a brush border made of microvilli: there are enzymes anchored to the microvilli called brush border enzymes. *venous blood from gi tract does not go directly to heart.
