1. Digestive System
Part 3

2. Small Intestine Duodenum: smallest section Jejunum: middle section
Stomach empties here
Jejunum: middle section
Ileum: final section
Joins large intestine at ileocecal sphincter

3. Small Intestine
21 feet of small intestine with added structures to increase surface area
Almost all absorption occurs here
Circular folds: folds in the mucosa to splash chyme and enhance absorption
Villi: fingerlike projections that contain capillaries, arteries, veins, all to move absorbed substances quickly

4. Small Intestine
Microvilli: smaller projections on the villi to further increase surface area and absorption

5. Small Intestine
Intestinal glands: in mucosa that secrete intestinal juice
Clear, yellowish liquid quickly reabsorbed
pH 7.6 with water and mucous
Enzymes for Chemical Digestion:
Maltase, sucrose, lactase: disac. To monosa.
Peptidases: peptides to amino acids
Ribonuclease, dioxyribonuclease: nucleic acids

6. Small Intestine Mechanical Digestion:
Segmentation: Concentration of chyme and juice that sloshes between areas of contraction of the muscularis
Perstalsis: moves the chyme steadily through intestines

7. Absorption in Small Intestine
Passage of digested substances and nutrients from the lumen to into the blood or lymph
90% of all absorption takes place here
Substances absorbed by diffusion, osmosis, and active transport

8. Absorption in Small Intestine
Carbohydrates absorbed as monosaccharides
Proteins absorbed as amino acids
Lipids absorbed as monoglycerides and fatty acids
Water —9 liters enter daily and 8 are reabsorbed

9. Large Intestine Main functions: Completion of absorption
Manufacture certain vitamins
Formation of feces
Elimination of feces

10. Large Intestine Cecum: pouch after ileocecal sphincter
Colon: ascending, transverse, descending, sigmoid
Surface area increased by pouch-like divisions: haustra
Rectum: last part, stores waste
Last inch is anal canal
Anus: opening to exterior
Two sphincters: internal anal sphincter (involuntary), external anal sphincter (voluntary)

11. Chemical Digestion of Lrg. Intestine
No enzymes
Bacteria ferment remaining carbohydrates
Release hydrogen, carbon dioxide, and methane
Vitamins K and some B’s are made and absorbed

12. Mechanical Digestion of Lrg. Intestine
Haustral churning: walls contract when haustra fill to a certain level
Peristalsis: slower than other areas
Mass peristalsis: strong muscular wave that pushes waste into the rectum

13. Absorption & Feces Formation
Chyme in the colon for 3-10 hrs. becomes rather solid: feces
Water, epithelial cells from mucosa, bacteria, undigested food
All but 100mL of the 1L of water is absorbed

14. Defecation Emptying of the rectum
Diarrhea: not enough water is absorbed because chyme travels too quickly through intestine
Can cause dehydration
Constipation: feces remains in colon too long, almost all the water is absorbed

15. Digestive System Attachments
Peritoneum & serosa: secrete slippery fluid to glide organs over each other
Outermost layer of GI tract
Visceral peritoneum: covers some organs in abdominal cavity
Parietal peritoneum: the walls of the abdominal cavity

16. Digestive System Attachments
Mesentery: binds small intestine to posterior abdominal wall
Mesacolon: binds large intestine to posterior abdominal wall
Falciform ligament: attaches liver to the anterior abdominal wall and diaphragm

17. Digestive Disorders Ulcers: lesions in a membrane
Peptic —from gastric juice
Gastric —in stomach
Esophageal —in esophagus
Duodenal —in small intestine
Appendicitis: inflammation of appendix

18. Digestive Disorders
Cirrhosis: scarred liver due to chronic inflammation
Colitis: inflammation of colon and rectum
Hernia: protrusion of an organ through a membrane or cavity wall