Capillaries

These are very tiny blood vessels, single cell layer walled tubes. This means that, the walls of capillaries are thin and this allows the exchange of materials like oxygen, carbon dioxide, glucose, amino acid etc. between blood and the cells.

As the blood flows through the capillaries, oxygen, hormones and food nutrients such as glucose and amino acids diffuse out of the blood into the cells.

The waste substances from the tissue enter the capillaries and are carried away from the tissue.

The movement of the substances between the blood and cells is due to diffusion. The blood that flows through the capillaries is slow, this is due to the time needed for substances to be exchanged between the blood and the cells.

The main function of the capillary is to allow the exchange of substances (oxygen, carbon dioxide, water, glucose, amino acids) between the blood and the body tissues.