What do the caplaries do?

Capillaries are the smallest blood vessels in the human body, forming a network that connects arterioles to venules. They play a vital role in the exchange of substances between the blood and the surrounding tissues.

The capillaries are lined with a single layer of endothelial cells, which are thin and porous enough to allow for the diffusion of small molecules such as oxygen, carbon dioxide, water, and glucose. The endothelial cells also have receptors for hormones and other signaling molecules, which allows them to regulate the exchange of substances across the capillary wall.

The capillaries are also responsible for the filtration of fluid from the blood into the surrounding tissues. This process is known as ultrafiltration, and it is driven by the hydrostatic pressure gradient between the blood and the tissues. The hydrostatic pressure is higher in the blood vessels than in the tissues, so fluid is forced out of the capillaries and into the tissues.

The capillaries are also responsible for the reabsorption of fluid from the tissues back into the blood. This process is known as absorption, and it is driven by the osmotic pressure gradient between the blood and the tissues. The osmotic pressure is higher in the blood vessels than in the tissues, so fluid is drawn back into the capillaries from the tissues.

The capillaries play a vital role in maintaining the fluid balance between the blood and the tissues. They also play a role in the exchange of nutrients and waste products between the blood and the tissues.