Examville - Physiology =digestion And Absorption In Git

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DIGESTION AND ABSORPTION IN GIT

THIS INCLUDES: 1. CARBOHYDRATE DIGESTION AND ABSORPTION 2. FATS DIGESTION AND ABSORPTION 3. PROTEINS 4. WATER AND ELECTROLYTES 1. CARBOHYDRATE DIGESTION: In Mouth, Starch -----------alpha amylase ------

Maltose.

In Stomach, Sucrose -------HCl---------

glucose and fructose.

In Duodenum, Starch ------------- Pancreatic alpha amylase-----

Maltose.

pH 7.1 In Small intestine, Disaccharides ----------------disaccharidases………..> monosaccharides.

Absorption: Monosaccharides in the gut lumen are absorbed in jejunum or proximal ileum. Absorption occurs by: Simple diffusion and Active transport Carriers: 1. Glucose binds to Sodium dependent glucose transporter-1. (SGLT-1) that carries glucose from the intestinal lumen to inside the cell . No energy is needed for this process. 2. Glucose is transported from the cell to blood capillaries by glucose transporter-2 (GLUT-2)

DIGESTION AND ABSORPTION OF FATS: In mouth, 1. Salivary lipase and gastric lipase digests triglycerides in stomach. 2. Bile salts and Pancreatic lipase acts in small intestine in digestion of fats. 3. Bile salts cause emulsification of fats so that fats can be hydrolyzed by lipase. 4. Triglycerides are hydrolyzed into diglycerides and further broken down into monoglycerides.

5. Micelle formation- Monoglycerides, bile salts and pancreatic electrolytes interact to form micelle. 6. Micelles are absorbed down the concentration gradient into luminal brush border. 7. Fatty acid and monoglycerides are re-esterified in the mucosal cells to triglycerides. Chylomicrons are formed which enter lymphatic system via thoracic duct and then into blood.

DIGESTION OF PROTEINS Pepsin hydrolyzes the proteins in stomach. Trypsin , chymotrypsin and carboxypeptidase act in duodenum on peptones and hydrolyze into free amino acids and lower peptides Erepsin act in small intestine on peptides and convert them into free amino acids

ABSORPTION OF AMINO ACIDS Absorption of amino acids occurs mainly in the duodenum and jejunum. Some absorption occurs in the large intestine. ABSORPTION OF WATER AND ELECTROLYTES Water- More than 90% of fluid is reabsorbed from GIT Sodium and potassium is reabsorbed from small intestine