What is the process of digestion in man?

What Is Digestion? Explain The Process In Man?

• Answer:

  Mouth - The food is mechanically digested through chewing .The mouth has salivary glands that produces certain enzymes such as salivary amylase and lysosome. These enzymes digest the carbohydrates; Polysaccharides (starch, glycogen) and Disaccharides (sucrose and lactose) and turn them to smaller polysaccharides and maltose. The chewed up food (bolus) is swallowed, passing through the esophagus until it reaches the stomach. Stomach - The stomach is a muscular sac that churns and mixes the food where the proteins are digested. The stomach has gastric glands that have Parietal cells (secretes HCl to increase acidity), Goblet cells that secretes mucus (the mucus covers the lining of the stomach so the acid will not harm the organ) and chief cells that secrete personage and a hormone called Gasteren that controls the gastric juices. The proteins are digested by pepsin and breaks it down to small polypeptides. Lumen of Small Intestine - The polysaccharides (the carbohydrate that was digested in the mouth) will be broken down (by Pancreatic amylase) to maltose and other disaccharides. The small polypeptides (the protein that was digested in the stomach) will be further broken down to smaller polypeptides and small peptides. Also, Nucleic Acid digestion and Lipid digestion takes place in the lumen. DNA and RNA are broken down to Nucleotides (by Pancreatic nuclease's). Fat Globules are broken down to fat droplets (by Bile salts) and the fat droplets are further broken down to Glycerol, fatty acids and glycerine's (by Pancreatic lipase). Epithelium of Small Intestine - The Maltose and Disaccharides (from lumen) are broken down to Monosaccharides (by Disaccharidases). The smaller peptides (from lumen) will be broken down to amino acids (by Dipeptidases, carboxypeptidase and aminopeptidase). And finally, the nucleotides (from lumen) will be broken down to Nucleosides (by Nucleotidases). The Nucleosides will then be broken down to Nitrogenous bases, sugars and phosphates (by Nucleosidases and phosphatases). Large Intestine - Reabsorption of important nutrients, water and electrolytes takes place as it travels through the large intestine (or colon). The unabsorbed matter (feces) is stored in the rectum until it is eliminated trhough the anus. The colon is home for bacteria that produce biotin, folic acid, vitamin K, several B-vitamins.