Circulation and Blood Vessels

Your heart and blood vessels make up your overall blood circulatory system. Your overall blood circulatory system consists of four subsystems.

Arterial circulation

Arterial circulation is that part of your overall blood circulatory system which involves the arteries like the aorta and pulmonary arteries.

Arteries are blood vessels that carry blood from the heart. Healthy arteries are strong and elastic. They become narrow between heartbeats and they help to keep your blood pressure consistent. This helps the blood circulate more efficiently through your body.

The arteries branch into smaller blood vessels called arterioles. Arteries and arterioles have strong, flexible walls that allow them to adjust the quantity and rate of blood flowing to various parts of your body.

Venous circulation

Venous circulation is the part of your overall blood circulatory system that involves veins, like the vena cavae and pulmonary veins. Veins are blood vessels that carry blood to your heart. Veins have thinner walls than arteries. Veins can increase in width as the amount of blood passing through them increases.

Capillary circulation

Capillary circulation is part of your circulatory system where oxygen, nutrients, and waste pass between your blood and parts of your body.

Capillaries connect the arterial and venous circulatory subsystems. Capillaries are tiny blood vessels.

The importance of the capillaries is their very thin walls. In contrast, arteries and veins and capillary walls are thin enough that oxygen and nutrients in the blood can pass through walls to the parts of your body that need them to function normally. Thin walls of capillaries also allow waste products, such as carbon dioxide, to pass from your body organs and tissues into the bloodstream where it's taken away to your lungs.

Pulmonary circulation

Pulmonary circulation is the movement of blood from the heart to the lungs and back again to the heart. Pulmonary circulation includes both arterial and venous circulation.

Blood with no oxygen is pumped to the lungs from the heart. Oxygen-rich blood moves from the lungs to the heart through the pulmonary veins.

Pulmonary circulation also includes the capillary blood circulation. Oxygen you breathe in air passes through your lungs into the blood through many capillaries in lungs. Oxygen-rich blood moves through your pulmonary veins on the left side of your heart and from the aorta to the rest of your body. The capillaries in the lungs remove carbon dioxide from the blood so that your lungs can breathe the carbon dioxide out into the air.