How the heart works

The heart is a muscle about the size of your fist. It works like a pump and beats 100,000 times a day. The heart has two sides, separated by an inner wall called the septum. The right side of the heart pumps blood to the lungs to pick up oxygen. Then, oxygen-rich blood returns from the lungs to the left side of the heart, and the left side pumps it to the body. The heart has four chambers and four valves and is connected to various blood vessels. Veins are the blood vessels that carry blood from the body to the heart. Arteries are the vessels that carry blood away from the heart to the body.

Heart chambers

The heart has four chambers or "rooms"—two on the left side of the heart and two on the right.

The atria are the two upper chambers that collect blood as it comes into the heart.
The ventricles are the two lower chambers that pump blood out of the heart to the lungs or other parts of the body.

Heart valves

Four valves control the flow of blood from the atria to the ventricles and from the ventricles into the two large arteries connected to the heart:

The tricuspid valve is in the right side of the heart, between the right atrium and the right ventricle.
The pulmonary valve is in the right side of the heart, between the right ventricle and the entrance to the pulmonary artery that carries blood to the lungs.
The mitral valve is in the left side of the heart, between the left atrium and the left ventricle.
The aortic valve is in the left side of the heart, between the left read more