The circulatory system comprises the vessels and muscles that help and control the flow of the blood around the body. The main parts of this system are the heart, arteries, capillaries and veins. As blood begins to circulate, it leaves the heart from the left ventricle and goes into the aorta. The aorta is the largest artery in the body. Oxygen-rich blood leaves the aorta and travels through the body via the arteries. Waste-rich blood returns to the heart through the veins.

The circulatory system is extremely important for sustaining life. It is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, maintenance of optimum pH, and the mobility of the elements, proteins and cells of the immune system.

This system may be seen as a blood distribution network, but some consider the circulatory system to be composed of the cardiovascular system, which distributes blood, and the lymphatic system, which distributes lymph. Humans, as well as other vertebrates, have a closed cardiovascular system, which means that the blood never leaves the network of arteries, veins and capillaries.

In advanced countries, the two leading causes of death are heart attacks and strokes. Each of these can directly result from an arterial system that has been slowly and progressively compromised by years of deterioration. Blood that flows up to the brain may find it hard to climb upwards, causing a person to feel light-headed and possibly to faint. Fainting is your brain’s natural request for more oxygen-rich blood.

It is very important that the body maintains a good level of blood circulation and that the circulatory system is functioning properly.