Tubes that act like a system of canals to carry blood to and from all parts of the body. The three main types of blood vessels are arteries, veins, and capillaries. When heart pumps these vessels carry the blood with oxygen and nutrients that the cells need or take away waste that the cells do not need.
The blood vessels are part of the circulatory system and function to transport blood throughout the body. The most important types, arteries and veins, carry blood away from or towards the heart, respectively.