Explain the functions of the large intestine: (i) absorption of water and vitamins, (ii) formation of faeces

Defaecation

9.5

Defaecation

Function of The Large Intestine

After the absorption of nutrients is completed in the ileum, undigested food, dead cells, epithelial cells, fibre and water enter the large intestine and move slowly through peristaltic action.
Fibre consists of cellulose walls of plant cells.
The large intestine carries out two main functions:
- absorption of water and vitamins.
- formation of faeces.

Absorption of Water and Vitamins

Substances absorbed are water, mineral salts, metabolic byproducts of some bacteria such as vitamin B, vitamin K and folic acid.

Formation of Faeces

After the water is absorbed, the remaining waste is a semisolid called faeces.
Faeces contains dead cells from the inner layer of the intestine, waste products such as bile pigments, bacteria and toxic substances.
The walls of the large intestine secrete mucus to smoothen the movement of faeces until the anus.
The movement of faeces takes about 12 to 24 hours before entering the rectum.
The faeces will accumulate in the rectum until the pressure in the rectum increases and triggers the need to expel faeces from the body.
The rectum muscles will contract to expel faeces from the anus.
This process is called defaecation.

9.5

Defaecation

Function of The Large Intestine

After the absorption of nutrients is completed in the ileum, undigested food, dead cells, epithelial cells, fibre and water enter the large intestine and move slowly through peristaltic action.
Fibre consists of cellulose walls of plant cells.
The large intestine carries out two main functions:
- absorption of water and vitamins.
- formation of faeces.

Absorption of Water and Vitamins

Substances absorbed are water, mineral salts, metabolic byproducts of some bacteria such as vitamin B, vitamin K and folic acid.

Formation of Faeces

After the water is absorbed, the remaining waste is a semisolid called faeces.
Faeces contains dead cells from the inner layer of the intestine, waste products such as bile pigments, bacteria and toxic substances.
The walls of the large intestine secrete mucus to smoothen the movement of faeces until the anus.
The movement of faeces takes about 12 to 24 hours before entering the rectum.
The faeces will accumulate in the rectum until the pressure in the rectum increases and triggers the need to expel faeces from the body.
The rectum muscles will contract to expel faeces from the anus.
This process is called defaecation.