BIBC 120 Lecture Notes - Portal Vein, Pancreatic Juice, Dietary Fiber
24 May 2018
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Week 2.3
1) SMALL INTESTINE
- digestion, vast majority of absorption occurs here
- bile produced in liver (stored in gallbladder) used for digestion of lipids in small
intestine
- pancreas secretes pancreatic juice which has digestive enzymes and produces
more bicarbonate (to neutralize acidic chyme coming into small intestine)
- need lots of surface area for nutrient absorption (plica circulares → villi →
enterocytes → microvilli)
i. mucosa and submucosa arranged in circular folds called plica circulares
ii. Plica circularies are covered with fingerlike projections called villi, each
villus contains a capillary network and a lymphatic vessel (lacteal); villi
made of absorptive cells called enterocytes (epithelial cells)
iii. Enterocytes covered with small projections (microvilli) which project into
the intestinal lumen (luminal brush border membrane). These draw
nutrients toward enterocytes where nutrient absorption takes place
- Fat soluble nutrient: lumen of intestine→ enterocyte→ through blood capillary
→lymphatic vessel to thoracic duct
- Water soluble nutrient: lumen of intestine→enterocyte→ blood capillary to liver
- drainage of blood from small intestine goes into hepatic portal vein which goes
back to liver (gives liver chance to process nutrients and detoxify)
2) Large intestine
- Ileocecal sphincter controls flow of undigested food residue between ileum of
small intestine (last part) and first part of large intestine (Cecum)
i. The rest of the large intestine is referred to as the colon
1) Reabsorption of:
i. water (dehydrate remaining material to feces)
ii. salts, Na+, K+, Cl-
2) Site of intestinal microbiota (bacteria)
i. Fermentation of soluble fiber → absorb some nutrients
3) Storage of feces for egestion/defecation
i. anal sphincter: controls movement of feces
ii. Feces: is 30% bacteria, 30% fiber, 10-20% fat, 25% protein, inorganic
material
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Document Summary
Digestion, vast majority of absorption occurs here. Bile produced in liver (stored in gallbladder) used for digestion of lipids in small intestine. Pancreas secretes pancreatic juice which has digestive enzymes and produces more bicarbonate (to neutralize acidic chyme coming into small intestine) These draw nutrients toward enterocytes where nutrient absorption takes place. Fat soluble nutrient: lumen of intestine enterocyte through blood capillary. Water soluble nutrient: lumen of intestine enterocyte blood capillary to liver. Drainage of blood from small intestine goes into hepatic portal vein which goes back to liver (gives liver chance to process nutrients and detoxify: large intestine.
