• Category:
  • Document type:
  • Level:
  • Page:
  • Words:

Topic: Circulatory system

Circulatory system

The heart is a powerful muscle that is composed of four chambers, two lower ventricles and two upper atria. It works as a pump by sending blood rich in oxygen to all the body parts. The human heart beats an approximately 100000 times in a day, during which it pumps over 4300 gallons of blood throughout the entire body (Iaizzo, 2009). It can be described as two pumps, side by side within one organ because it is divided into two main parts, the left side and the right side. Each side contains two chambers, the lower chambers known as ventricles and the upper chambers known as an atrium.

On the right side, the right ventricle receives deoxygenated blood as the right atrium contracts. During this process, a valve known as the pulmonary valve is closed, allowing the right ventricle to fill up. When right ventricle is full, it contract. When the ventricle contracts, a valve known as the tricuspid valve closes after which the pulmonary valve opens. Backflow of blood into the atrium is prevented by the closure of the tricuspid valve. The opening of the pulmonary valve lets the blood through to the pulmonary artery, toward the lungs so that the blood can be oxygenated (Starr, 2012).

On the left side, blood rich in oxygen enters the left atrium through the pulmonary veins. When the left atrium is filled up, the bicuspid valve opens, and blood is forced to the left ventricle filling it. The left ventricle contracts, forcing blood through the aorta, which carries blood to all the body parts except the lungs. The aortic valve opens allowing the flow of blood through the artery. Since the blood is pumped with a lot of pressure, the walls of the aorta expand, and its muscles stretch. When the ventricle is almost empty, the semi-lunar valve closes, preventing the flow of blood back into the heart (Roberts & King, 2002).


IAIZZO, P. A. (2009). Handbook of cardiac anatomy, physiology, and devices. New York, NY, Springer.

ROBERTS, M. B. V., & KING, T. J. (2002). Biology: a functional approach. Students’ manual. Walton-on-Thames, Surrey, Nelson.

STARR, L. (2012). Animal structure and function. Pacific Grove, Calif, Brooks/Cole.

TOOLE, G., & TOOLE, S. (1997). Advanced human and social biology. Cheltenham, Stanley Thornes.