The schematic representation of the circulatory system of human body is explained as follows. The blood is carried to the various parts of the body through blood vessels which are hollow tubes. There are three types of blood vessels.
- Arteries: The function of arteries is to carry the oxygenated blood away from the heart
- Veins: These carry the blood to the heart which is to be oxygenated.
Arteries are tough elastic tubes and as they move away from the heart they divide into smaller tissues. The smallest arteries are called arterioles which carry bright red blood. The colour comes from the oxygen that it carries. The veins carry dark red blood that doesn’t have much oxygen. The smallest veins are called venules. Veins need not to be as strong as arteries because as the blood is returned to the heart, it is under less pressure.
In the circulatory system, the atrium collects the blood and pumps it into the ventricles. So the heart pumps the blood through pulmonary circulation to the lungs and through systemic circulation to the other parts of the body at an average rate of 72 times per minute for a normal adult. The system of blood vessels that ensures the supply of oxygenated blood from the left ventricle to all the body organs and return of deoxygenated blood to the right atrium is called systemic circulation. The main purpose of such a circulation is to transport oxygen as well as nutrients to the body tissues and remove carbon dioxide and harmful wastes from it.
The pulmonary arteries supply the deoxygenated blood from the right ventricle to the lungs and pulmonary veins bring back the oxygenated blood to the left auricle. Blood is also supplied to the heart muscles by the coronary arteries forming the coronary circulation. It is a pathway of blood through the arteries from the aorta arising from the heart and returning to the right atrium.