Venule | Vein

Venule

The smallest veins in the human body are called venules. The wall structure of this vein/venule is similar to that of the capillary, but the diameter is much larger (10-30 micrometers). A venule has no muscle layer.

Often the wall of a venule is not completely sealed, there are no connections between the individual cells of the vessel wall (endothelial cells). As a result, white blood cells can enter the surrounding tissue and fight pathogens and centres of inflammation. The passage of the white blood cells through the vascular wall of the venules is called diapedesis.

Jugular vein

A jugular vein has the ability to close completely. This possibility exists because jugular veins have an additional longitudinal muscle layer in the innermost vascular wall layer (tunica intima). However, this is the exception; normal blood vessels cannot close up. This type of vein is mainly found in the intestine and in the adrenal medulla.

Portal vein system

The portal vein (vena portae) collects venous blood from all unpaired abdominal organs (stomach, intestine, pancreas and spleen) and carries it to the liver. There, the blood flows through the capillary system of the liver, where various metabolic processes take place. The venous blood then flows via the hepatic veins (Venae hepatis) into the inferior vena cava (Vena cava inferior).

Venous bulge (Sinus venosus)

In the human body there are numerous venous blood collection areas. These are called sinuses (plural: sinus), which means bulge. For example, the coronary sinus, a collection point for the venous blood of the heart, is located at the heart.

Venous plexus (Plexus venosus)

The human body also contains many tiny meshes and networks of venous vessels. Often small organs and glands are surrounded by a venous plexus, thus ensuring that venous blood can flow evenly from all parts of the organ. Likewise, many turns around an organ, for example in the testicles, create a very large contact surface between the organ and the blood vessels, which leads to a more efficient exchange of substances.