Venules are small veins that serve as a link between larger veins and capillaries. These blood vessels therefore join the veins at one end and the capillaries at the other.
It can be said that venules are small veins responsible for collecting blood from capillaries and taking it to common veins. In this way, venules play a very important role in returning blood to the heart. It is important to remember at this point that blood is a liquid made up of plasma and different types of cells in suspension (platelets, red blood cells, white blood cells). Nutrients and oxygen are distributed throughout the body through the blood and waste substances are collected.
As for the structure of venules, it is similar to that of veins. Venules have an inner layer (endothelium) and an adventitial or outer layer (a fibrous connective tissue), although they lack the elastic tissue that, in veins, is located between the two sectors. It is important to mention that venules, veins and venous capillaries constitute what is known as the venous system. Its function is to transport already deoxygenated blood that carries waste and carbon dioxide, making a path parallel to that of the arterial system, although in the opposite direction. In short, venules are a kind of blood vessel. Among the vessels we also find veins, capillaries, arterioles and arteries. In the specific case of venules, through them begins the return of blood to the heart after passing through the capillaries.