The Heart

Illustration by Steven P. Goldberg, MD
Copyright © 2012 STS

The heart’s job is to collect blood from all areas of the body, pump the blood to the lungs where it receives oxygen, collect the oxygen-rich blood from the lungs, and pump it to all areas of the body.

The heart is composed of four chambers or rooms. The top two chambers are called atriums, and these are the collecting chambers of the heart. The bottom two chambers are called ventricles, and these are the pumping chambers of the heart.

The right side of the heart collects oxygen-poor blood from the body and pumps it to the lungs. The left side of the heart collects oxygen-rich blood from the lungs and pumps it to the body. More specifically, the right atrium collects oxygen-poor blood from the body through two large veins called the superior vena cava (SVC) and inferior vena cava (IVC). The blood flows from the right atrium to the right ventricle through the tricuspid valve. The valves in the heart, including the tricuspid valve, are designed to keep the blood flowing in the right direction and prevent it from flowing backwards. The right ventricle pumps the oxygen-poor blood through the pulmonary valve into the pulmonary artery, which carries the blood to the lungs.

The left atrium collects the oxygen-rich blood from the lungs through the pulmonary veins. The blood flows from the left atrium to the left ventricle through the mitral valve. The left ventricle pumps the oxygen-rich blood through the aortic valve and the aorta to the rest of the body.

The left and right sides of the heart are divided by walls called septums. There is an atrial septum that separates the right and left atriums, and a ventricular septum that separates the right and left ventricles.

Because the left ventricle has to do the big job of pumping blood to all parts of the body, the left ventricular muscle is thick and generates high pressure in the blood stream. When blood pressure is taken in the arm using a blood pressure cuff, what is being measured is the pressure in the artery in the arm that is generated by the left ventricle. In a normal heart, the right ventricle has an easier job, since it pumps blood only to the lungs, which are next to the heart. So, the muscle in the right ventricle is usually not so thick and generates much less pressure than the left ventricle.

Written by Jeffrey P. Jacobs, MD and Heidi Hess, RN - Reviewed September 2012

|||