Human DIGESTION AND ABSORPTION

DIGESTION  AND ABSORPTION

The physiological process by which, in the presence of enzyme and other substances, the complex large molecules of organic food masses are broken down into simple, smaller molecules, e.9., carbohydrate into glucose, protein into amino acids and fats into fatty acids and glycerol, that can be absorbed by the body cells is called digestion. Digestion and absorption occurs in the alimentary canal, or more plainly the gut, which runs from the mouth to the anus. As the gut is continuous with the outside surface of the body, the food in the gut is considered to be 'outside' of the body. The type of digestion takes place in the alimentary canal is called extracellular digestion. Food can only be absorbed into the body after it has been ingested and broken down physically by the teeth and muscles of the gut wall (mechanical digestion). and chemically by its enzymes into molecules of a suitably small size to be absorbed through the gut wall (chemical digestion). From here the nutrients enter the blood or lymph and are delivered to the cells of the body tissues where they undergo assimilation. Undigested food is egested through the anus. The system responsible for the ingestion, digestion, absorption and removal of undigested food is called digestive system. The digestive system consists of alimentary canal and the digestive glands.