Absorption Of Food

Absorption Of Food its use

The digested food is absorbed mainly in the small intestine. Absorption is the process by which the products of digestion are taken into the blood stream.

The intestinal lining is provided with finger-like projections called villi. The absorption surface is greatly increased by presence of millions of villi.

Each villus is supplied with blood capillaries and a lymph vessel or lacteal.

Absorption is conducted by both active and passive transport processes. It first enters mucosal cells and then passes into submucosa.

No absorption occurs in stomach except that of ethanol.

Small intestine :

Fatty acids, glycerol, water, inorganic salts and vitamins are also absorbed in the small intestine. The villi are bathed in the digested food products contained in the lumen of intestine and the food diffuses through the epithelium into the blood vessels.

In villi, monosaccharides, peptides and amino acids are absorbed either by diffusion or active transport into the blood capillaries. These blood capillaries converge to form the hepatic portal vein which delivers the absorbed food to the liver.

Large intestine:

No enzymes are secreted here. This part is concerned with the absorption of water. The undigested semi-solid food which remains in small intestine is passed on into large intestine. In the large intestine water is absorbed from it.

The undigested waste called faeces is stored in the rectum from where it is egested through the anus. The process of elimination of undigested food is called defaecation. The roughage in the diet helps in promoting the movement of bowels.