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Explain the process of digestion and absorption of food in man?

Answer» \xa0The major organs or structures that coordinate digestion within the human body include the mouth, esophagus, stomach, small and large intestine, and liver.\xa0Mouth-\xa0The mouth\xa0is a specialized organ for receiving food and breaking up large organic masses. In the mouth, food is changed mechanically by biting and chewing.\xa0Food is moistened by saliva.\xa0The saliva contains an enzyme called\xa0amylase, which digests starch\xa0into\xa0maltose. During chewing, the tongue moves food about and manipulates it into a mass called a\xa0bolus. The bolus is pushed back into the pharynx\xa0and is forced through the opening to the esophagus.Esophagus-\xa0The bolus of food moves through the esophagus by peristalsisStomach - The\xa0stomach\xa0is an expandable pouch located high in the abdominal cavity. Layers of stomach muscle contract and churn the bolus of food with gastric juices to form a soupy liquid called chyme. The stomach stores food and prepares it for further digestion. In addition, the stomach plays a role in protein digestion. Gastric glands called\xa0chief cells\xa0secrete pepsinogen, which is converted to\xa0pepsin in the presence of hydrochloric acid.\xa0The pepsin then digests large proteins into smaller proteins called peptides. To protect the stomach lining from the acid stomach\xa0cells secretes mucus that lines the stomach cavity.Small intestine: The\xa0chyme enters from\xa0stomach to the small intestine. The three parts of small intestine are\xa0duodenum, jejunum and\xa0ileum.\xa0The inner surface of the small intestine contains numerous fingerlike projections called\xa0villi. Each villus has projections of cells called\xa0microvilli\xa0to increase the surface area.Most chemical digestion takes place in the duodenum. In this region, enzymes digest nutrients into simpler forms that can be absorbed. Intestinal enzymes are supplemented by enzymes from the pancreas. In addition, bile enters the small intestine from the gall bladder to assist in fat digestion.The enzymes functioning in carbohydrate digestion include amylase (for starch), maltase (for maltose), sucrase (for sucrose) and lactase (for lactose).For fats, the principal enzyme is lipase. Before this enzyme can act, the large globules of fat must be broken into smaller droplets by bile.Protein digestion is accomplished by several enzymes, including two pancreatic enzymes: trypsin and chymotrypsin. Peptides are broken into smaller peptides, and peptidases reduce the enzymes to amino acids.Nucleases digest nucleic acids into nucleotides in the small intestine also.The products of digestion enter cells of the villi, move across the cells, and enter blood vessels called capillaries. Diffusion accounts for the movement of many nutrients, but active transport is responsible for the movement of glucose and amino acids. The products of fat digestion pass as small droplets of fat into lacteals, which are branches of the lymphatic system.Substances that have not been digested or absorbed then pass into the large intestine.Large intestine -\xa0The large intestine\'s chief functions are to absorb water and to store, process, and eliminate the residue following digestion and absorption. The intestinal matter remaining after water has been reclaimed is known as\xa0feces.\xa0The feces are stored in the rectum and passed out through the **** to complete the digestion process.


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