Absorption of digested products
- Absorption is the process by which the end products of digestion pass through the intestinal mucosa into the blood or lymph.
- Some of the substances like fructose and some amino acids are absorbed with the help of the carrier ions like Na+ and this mechanism is called the facilitated transport.
- Transport of water depends upon the osmotic gradient and active transport occurs against the concentration gradient and hence requires energy.
- Fatty acids and glycerol being insoluble are first incorporated into small droplets called micelles which move into the intestinal mucosa.
- Micelles are re-formed into very small protein coated fat globules called the chylomicrons which are transported into the lymph vessels (lacteals) in the villi.
- Absorption of substances takes place in different parts of the alimentary canal, like mouth, stomach, small intestine and large intestine.
- The absorbed substances finally reach the tissues which utilise them for their activities. This process is called assimilation.
- The egestion of faeces to the outside through the anal opening (defaecation) is a voluntary process and is carried out by a mass peristaltic movement.
Fig. Lymph vessels in the villi