Why the exchange of materials between the blood and tissues occur through capillaries?

Dear Student,

Capillaries are microscopic blood vessels that connect arterioles and venules.Substances move in and out of the arteries as blood moves through the arteries and exchanges materials with the tissue cells.

The exchange of materials between the blood and the tissues takes place through capillaries because:

• They are composed of a single layer of endothelial cells, which allows fast diffusion of substances from the blood to the tissue cells
• Capillaries are interlinked with every cell and are very close to the cells, which reduces the time and path for diffusion of substances.
• The length of the capillaries is huge, which provides a very high surface area for diffusion to take place.

Hope it helps.