Biology of the blood vessels

[Julene]

The heart and blood vessels constitute the cardiovascular (circulatory) system. The blood circulating in this system delivers oxygen and nutrients to the tissues of the body and removes waste products from the tissues.
The blood vessels consist of

Arteries
Arterioles
Capillaries
Venules
Veins

All blood is carried in these vessels.
If a blood vessel breaks, tears, or is cut, blood leaks out, causing bleeding. Blood may flow out of the body, as external bleeding, or it may flow into the spaces around organs or directly into organs, as internal bleeding.