Blood Circulation

Today onwards, we going to focus on our body blood circulation. The circulation is a closed network of blood vessels, in other words, tubes which carry blood around the body. At its centre is the heart, a mascular pump with the job of keeping the blood in constant motion.

The circulation of blood throughout our bodies is automatically regulated according to our activities, so that it is always in the places where it is most needed.

Blood starts its journey round the circulation by leaving the left side of the heart through the large artery known as the aorta.

At this stage, blood is rich in oxygen, food broken down into the microscopically small components known as molecules, and other important substances such as hormones, the body's chemical 'messengers'. On the early part of its journey blood flows through relatively large tubes called arteries, and then it passes into smaller vessels known as arterioles. These lead to every organ and tissue in the body, including the heart itself.

From the arterioles, the blood enters a vast network of minute vessels called the capillaries. It is here that oxygen and life-maintaining molecules are given up in return for the waste products of the body's activities.