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

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Presentation on theme: "Small Intestine Duodenum: smallest section – Stomach empties here Jejunum: middle section Ileum: final section – Joins large intestine at ileocecal sphincter."— Presentation transcript:

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2 Small Intestine Duodenum: smallest 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


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