Heart Chambers

What Do Heart Chambers Do?

The inside of your heart is divided into four sections, or chambers. The chambers are like separate rooms that hold the blood before pumping it out to the body. Each chamber has doors (valves) that let blood pass in and out.

The Atria—Receiving Blood From the Body

The two upper chambers in your heart are called the atria. (Just one of these chambers is called an atrium.) When blood flows into your heart from the body or lungs, it always flows into either the right or left atrium. When blood flows into your heart from the lungs, it always flows into the left atrium. Blood flows into both atria at the same time. When the atria are full with blood, they contract and push blood down into the ventricles at the same time.

The Ventricles—Pumping Blood Out to the Body

The two lower chambers in your heart are called ventricles. The ventricles are known as the pumping chambers of your heart. When blood leaves your heart to go to your lungs, it is always pumped out from the right ventricle. When blood leaves your heart to go to the rest of your body, it is always pumped out from the left ventricle. The ventricles are larger than the atria. The ventricles are also very strong because they have to pump hard enough to push blood throughout your entire body.

Your Heart’s Right and Left Sides

Sometimes the right and left sides of your heart are called your right heart and left heart. The right atrium and right ventricle are, of course, on the right side of your heart. (It’s the same side as your right arm.) The left atrium and left ventricle are on the left side of your heart. However, when you look at a picture of the heart, the right heart is on the left.

A wall called the septum separates the right and left sides of your heart. The septum also separates the oxygen-rich blood from the oxygen-poor blood in your heart. Blood that hasn’t yet been to the lungs (oxygen-poor blood) stays on the right side of the septum. Blood returning from the lungs (oxygen-rich blood) stays on the left side of the septum.