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How the Heart Works
Posted: May 1, 2009
Your heart is a muscle about the size of your fist. It works like a pump and it is always pumping blood throughout the body. The average heart beats 100,000 times a day.
The heart has a left and right side, separated by a wall of muscle called the septum. Blood vessels called veins bring blood to the heart, while other blood vessels called arteries carry blood away from the heart. Here is what happens:
- Blood from your body enters the right side of your heart through veins. The blood is dark because it has given all its oxygen to your body.
- The right side of the heart pumps the blood through the pulmonary artery to your lungs to pick up oxygen.
- After traveling through the lungs, the blood turns bright red because it is rich in oxygen.
- The oxygen-rich blood then returns to the left side of your heart and is pumped out to your body through the large artery called the aorta.
Heart chambers
The heart has four chambers or "rooms.” There are two on each side. The upper chambers are called atria and the lower chambers are called ventricles. The atria collect blood as it comes into the heart. As your heart beats, blood is pumped from the atria through valves down into the ventricles. Then, blood is pumped from the ventricles out of the heart through different valves.
Heart valves
The heart has four valves that open and close, like doors, to control the flow of blood through the heart in one direction. The four valves are:
- Tricuspid valve, between the right atrium and the right ventricle.
- Pulmonary valve, between the right ventricle and the entrance to the pulmonary artery.
- Mitral valve, between the left atrium and the left ventricle.
- Aortic valve, between the left ventricle and the entrance to the aorta.
Arteries
The arteries attached to the heart are:
- The aorta, the main artery that carries oxygen-rich blood from the left side of the heart to the body.
- The pulmonary artery, which carries blood from the right side of the heart to the lungs to pick up oxygen.
The heart also has arteries on its outside surface called the coronary arteries. These important arteries supply the heart muscle itself with the oxygen-rich blood it needs to work normally.
Source: National Heart, Lung and Blood Institute
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