largest cause of cancer deaths in males Forms from benign mucosal tumors called polyps Polyp formation increases with age Regular examination necessary if > age 50
Malabsorption of Nutrients • Causes – Anything that interferes with delivery of bile or pancreatic juice – Damaged intestinal mucosa (e.g., bacterial infection)
Malabsorption of Nutrients • Gluten-sensitive enteropathy (celiac disease) – Gluten damages the intestinal villi and brush border – Treated by eliminating gluten from the diet (all grains but rice and corn)
Fat digestion Figure 23.32 (3 of 4) Small intestine Small intestine Foodstuf f Unemulsified fats Emulsification by the detergent action of bile salts ducted in from the liver Pancreatic lipases Monoglycerides and fatty acids Glycerol and fatty acids Path of absorption Enzyme(s) and source Site of action • Fatty acids and monoglycerides enter the intestinal cells via diffusion. • Fatty acids and monoglycerides are recombined to form triglycerides and then combined with other lipids and proteins within the cells, and the resulting chylomicrons are extruded by exocytosis. • The chylomicrons enter the lacteals of the villi and are transported to the systemic circulation via the lymph in the thoracic duct. • Some short-chain fatty acids are absorbed, move into the capillary blood in the villi by diffusion, and are transported to the liver via the hepatic portal vein.
Bacteria Mucosa layer of stomach (a) A gastric ulcer lesion (b) H. pylori bacteria Figure 23.16
Ulcers = erosions of stomach wall • Predisposing factors: • “old blames”: • 90% recurrent ulcers: • Problem w/ theory … • TTX :
Developmental Considerations : EMBRYONIC DEVELOPMENT 3 rd week: gut formation; mouth and anus nearly formed 8 th week: accessory organ formation FETAL DEVELOPMENT Nutrition: via placenta GI tract development stimulated by: AT BIRTH Feeding: Enhanced by: rooting reflex sucking reflex OLD AGE
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