digestion &absorption

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Digestion and Absorption

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Digestion is the process where complex organic molecules of food stuffs are converted to smaller molecules which are easily absorbed by GIT

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Gastro Intestinal tract Mouth - Saliva  amylase Stomach - Hcl, Gastric enzymes Pancrease - NaHCo3 and many enzymes Liver - Bile acids Small Intestine - Final digestion and Absorption

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Saliva - Secreted by Salivary glands Contains - 99.5% water - Mucin - Salivary enzymes ( Salivary amylase, Lingual Lipase)

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Gastric Juice - 97 – 99% water - 0.2 – 0.5 % Hcl with a pH - 1 - Mucin, Inorganic salts. - Digestive enzymes (Rennin, Pepsin, Lipase)

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Bile - Liver produces Bile Function: Emulsification Neutralization of acid Excretion

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Pancreatic Juice - non viscid watery fluid. contains - Proteins, Organic & Inorganic compounds - Many enzymes Trypsin, Chymotrypsin, Elastase, Carboxypeptidase, Amylase, Lipase, Phospholipases, Cholesterolesterases, Ribonuclease

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Intestinal Juice Secreted by the glands of Brunner & Luberkerhin - Aminopeptidases - Disacharidases - Oligosacharidases -  - glucosidases - polynucleotidases - Phospholipases

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Digestion of Carbohydrates The major Dietary carbohydrates are Starch Glycogen Lactose Sucrose

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Digestion of carbohydrates in mouth Salivary  - amylase (ptyalin) acts on 1,4 glycosidic bonds randomly and the products are limitdextrins, maltotriose, maltose. No carbohydrate Digestion in stomach

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Digestion in Small Intestine The acidic contents are neutralized by NaHCo3 present in PancreaticJuice. Pancreatic amylase acts on starch and cleaves  1,4 glycoside bonds and the resultant products are Disaccharides and Oligosaccharides. Oligosaccharidases, Disaccharidases, Sucrase & Lactase finally digest and the products to monosaccharides.

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Absorption of monosaccharides The end products of Carbohydrate digestion are glucose fructose galactose Absorption of carbohydrates mostly takes place in Duodenum and upper jejunum.

MECHANISM OF ABSORPTION : 

MECHANISM OF ABSORPTION Glucose is transported into the intestinal mucosal cells by carrier mediated and energy requiring process. Phlorizin blocks the sodium dependent transport of glucose.

Abnormalities of carbohydrate digestion. : 

Abnormalities of carbohydrate digestion. Lactose intolerance - lactase deficiency lactose accumulates in the gut,it is acted upon by bacteria to produce organic acids, and these acids take up water from intestinal cells by osmotic effect and produce diarrhea. Benedicts test is +ve for stool samples. Treatment: restriction of milk and milk products.

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Digestion and Absorption of PROTEINS Daily Protein load for digestion is around 100 – 200 gms - Dietary Protein - 50 – 100 gms/day -Endogenous Protein - 30 – 100 gms/day Proteins are degraded by Hydrolases, called as Peptidases Endopeptidases – which attack internal peptides and release peptide fragments. Pepsin Trypsin Exopeptidases - which attack peptide bonds of terminal amino acids Carboxypeptidases Amino peptidases

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Proteins are not digested in Mouth Digestion in Stomach Hcl Gastric Juice Proenzyme pepsinogen HCL has 2 functions It denatures Protein It kill microorganisms Pepsin: It is produced in inactive form pepsinogen It is converted to pepsin by Hcl & Pepsin molecules ( Auto catalysis) Pepsin is acid stable – active at very low pH i.e., 2.0

Rennin ( Chymosin) : 

Rennin ( Chymosin) It is found in the stomach of Infants & children It converts casein Calcium Paracaseinate It is involved in curdling of milk Rennin is absent in adults.

Pancreatic Digestion of Proteins : 

Pancreatic Digestion of Proteins NaHCo3 Pancreatic Juice Trypsin Chymotrypsin Elastase Endopeptidases Secretion of Pancreatic is stimulated by Cholecystokinin and Pancreozymin All the Pancreatic enzymes are active at neutral pH. All these enzymes are secreted as inactive forms, these are converted to active form by ‘Enteropeptidase’ (Enterokinase)

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Intestinal Digestion of Proteins Complete digestion of proteins is brought by enzymes present in Intestinal Juice Aminopeptidases Dipeptidases

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Absorption of Amino acids Mainly in small intestine Energy requiring process . Five different transporters are present 1. Neutral Amino Acid 2. Basic Amino Acid 3 . Acidic Amino Acid 4. Iminoacids and Glycine 5.  - Amino acid