Circulatory system

The circulatory system (also called the cardiovascular system) is the body system that moves blood around the body. It consists of the heart and blood vessels. The blood carries various materials that the body needs, and takes away waste and harmful substances.

Blood vessels that take blood away from the heart are arteries. Arteries divide into smaller arteries as they go away from the heart. The smaller arteries that connect to the capillaries, are called arterioles.

Blood vessels that take blood towards the heart are veins. Veins get bigger as they go towards the heart. The smallest veins are called venules. Pronounced (VEHN-yools)

Capillaries go between arteries and veins. Capillaries are quite thin, hence the name which comes from the Latin capillus^[1] meaning "hair."

So blood moves: heart→artery→arteriole→capillary→venule→vein→heart. This is called circulation. There are two different circulations in the circulatory system. The systemic circulation is how blood goes to most of the body. The pulmonary circulation is how blood goes through the lungs. (Pulmonary means ¨about the lungs¨). This is how it works in mammals, including humans. Circulatory systems of other vertebrates differ somewhat.

1. ↑ Harper, Douglas. "Online Etymology Dictionary". Online Etymology Dictionary.