digestive system digestive system. introduction overview gastrointestinal tract (gi tract) – from...
Post on 17-Dec-2015
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Overview
• Gastrointestinal Tract (GI Tract) – from mouth to anus
• Accessory organs – teeth, tongue, salivary glands, liver, gallbladder, pancrea s
Functions
• Ingestion• Secretion – H20, enzymes, acid, buffers• Mixing and propulsion – peristalsis• Digestion – mechanical and chemical
breakdown• Absorption• Defecation
Mouth, Pharynx & Esophagus
• Mouth includes teeth, tongue, salivary glands
• Pharynx – throat; swallowing reflex• Esophagus – muscular tube; transports
food to the stomach; some absorption
Stomach
• J-shaped enlargement of the GI tract• Gastric Juice:– Mucus– Pepsinogen– HCl– Intrinsic factor
• Chyme: thick liquid of gastric juice and food
Stomach4 Layers of stomach wall• Mucosa– Rugae – folds of stomach wall– Columnar epithelium – secretes mucus
• Secretory Cells– Mucus cells– Parietal Cells – HCl and Intrinsic factor (vit. B12
absorption)– Chief cells – secrete pepsinogen– G cells – secrete gastrin
Small Intestine
• 3 sections: duodenum, jejunum, ileum• Most of digestion and absorption takes place
here• Absorptive cells in the microvilli• Absorption of sugars, amino acids, H2O, lipids,
vitamins• Digestive enzymes come from pancreas and
small intestine
Small Intestine
Digestive enzymes:• Maltase, sucrase, lactase• LipaseAbsorption:• Simple sugars, amino acids, ions, H2O, lipids,
and vitamins
Large Intestine
• 1st section at opening of ileum – cecum; appendix attached
• 4 regions: ascending, transverse, descending, and sigmoid colon
• Final stage of digestion (work of bacteria)• Absorption of H2O, vitamins• Chyme → feces → defecation (elimination)
Pancreas
• Pancreatic juice: H2O, salts, HCO3-, enzymes
• Enzymes:– Amylase; breaks down starches– Trypsin; breaks down proteins (inactive form)– Lipase; breaks down fats
Liver & Gallbladder
• Bile: emulsifies large lipid globules; stored in gallbladder
• Functions:– Carbohydrate metabolism – blood glucose levels– Lipid metabolism – cholesterol production, etc.– Protein metabolism – ATP production, converting
ammonia into urea, plasma protein production
Liver & Gallbladder
• Functions (continued)– Processes drugs and hormones; detox center– Stores minerals and vitamins– Activates vitamin D
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