Blood Vessels

Three types of blood vessels may be found in the circulatory system. These are the

a) arteries, which carry blood from the heart to either the lungs or body tissues,

b) the capillaries which are minute vessels which deliver nutrients, water, and oxygen to the body cells and pick up cellular wastes,

c) and the veins which transport blood back to the heart.

In most cases, arteries are delivering oxygenated blood and nutrients to the body tissues, while veins transport deoxygenated blood & cellular wastes back to the heart. However, this does not always hold true, as the pulmonary arteries transport deoxygenated blood from the heart to the lungs, and the pulmonary veins transport oxygenated blood back to the heart from the lungs.

The structure of arteries, capillaries, and veins is reflected in the position as well as their function within the circulatory system. These differences in structure and function are illustrated in the diagrams below.