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Digestive System Part 3.

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Presentation on theme: "Digestive System Part 3."— Presentation transcript:

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

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