What is the main function of capillaries?

Hint: Capillaries are the very small blood vessels that connect the blood flow system in our body as well as tissues in our body. They are made up of only the tunica interna layer. Capillaries have very fine capillary pores. Capillaries connect the arteries with the veins.

Complete answer: The capillaries are the tiny blood vessels that help in the exchange of oxygen, nutrients, waste between the tissues and the blood. Due to this reason, more active tissues in the body have a greater number of capillaries as compared to less active tissues of the body. The exchange of various substances between the blood and the tissues through the capillaries occurs through two main processes. These two processes are namely diffusion and pinocytosis. The capillaries are made up of a layer of cells called the endothelium. This endothelium is surrounded by a basement layer. This composition makes the capillaries much leakier than the other blood vessels that help in the transfer of nutrients, waste in between blood and tissues. The human body has mainly three types of capillaries known as the fenestrated capillaries, continuous capillaries, and the sinusoid capillaries.

Note: The human body has three kinds of blood vessels. These three types of blood vessels are arteries, veins, and capillaries. Arteries are the blood vessels that carry the oxygenated blood. Arteries are very deep-seated in the body. They have no valves present in them. Moreover, they are distributing blood vessels. Veins are the blood vessels that carry the deoxygenated blood. Veins are superficial vessels in the body. They have valves present in them. Moreover, they are collecting blood vessels.