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2. APPENDIX Blind tube off cecum
No important digestive functions in humans

3. PERITONEUM (FIGURE 15-14)
Definitions—peritoneum, serous membrane lining abdominal cavity and covering abdominal organs; parietal layer of peritoneum lines abdominal cavity; visceral layer of peritoneum covers abdominal organs; peritoneal space lies between parietal and visceral layers
Extensions—largest are the mesentery and greater omentum
Mesentery is extension of parietal peritoneum, which attaches most of small intestine to posterior abdominal wall
Greater omentum, or “lace apron,” hangs down from lower edge of stomach and transverse colon over intestines
X-ray studies of the GI tract—radiopaque contrast medium used to help visualize structures in study images

5. DIGESTION (TABLE 15-2)
Definition—transforms foods into substances that can be absorbed and used by cells
Mechanical digestion—chewing (mastication), swallowing (deglutition), and peristalsis break food into tiny particles, mix them well with digestive juices, and move them along the digestive tract
Chemical digestion—breaks up large food molecules into compounds that have smaller molecules; brought about by digestive enzymes (Figure 15-15)
Enzymes and chemical digestion
Enzymes are specialized protein molecules that act as catalysts
Breakdown process called hydrolysis

7. DIGESTION Carbohydrate digestion—mainly in small intestine
Pancreatic amylase—breaks polysaccharides down to disaccharides
Intestinal juice enzymes
Maltase—changes maltose to glucose
Sucrase—changes sucrose to glucose
Lactase—changes lactose to glucose

8. DIGESTION
Protein digestion—starts in stomach; completed in small intestine
Gastric juice enzyme pepsin partially digests proteins
Pancreatic enzyme, trypsin, continues digestion of proteins
Intestinal enzymes, peptidases, complete digestion of partially digested proteins and convert them to amino acids
Fat digestion
Bile contains no enzymes but emulsifies fats (breaks fat droplets into very small droplets)
Pancreatic lipase changes emulsified fats to fatty acids and glycerol in small intestine

9. ABSORPTION
Definition—process by which digested food moves from intestine into blood or lymph
Foods and most water minerals and vitamins are absorbed from small intestine; some water and vitamin K also absorbed from large intestine
Surface area absorption
Structural adaptations increase absorptive surface area
Fractal geometry—study of fragmented geometric irregular shapes such as those in lining of intestine