The Heart's Chambers and Valves

Human heart and valves

The function of the heart is to pump the blood that bathes every organ of the body. The blood carries the oxygen and nutrients vital to the tissues and removes waste products. If the pumping action of the heart is disrupted, the body's organs begin to fail very quickly. So life itself is dependent on the efficient, continuous operation of the heart.

The heart is a muscular organ roughly the size of your fist.

As the heart muscle contracts or squeezes, it propels the blood out into the vascular system. The heart's chambers and valves are arranged to direct the flow of the blood as the heart beats.

Heart’s Chambers and Valves

The heart has four chambers. The two ventricles (right and left) are muscular chambers that propel the blood out of the heart. The right ventricle pumps blood to the lungs, and the left ventricle pumps blood to all other organs.

The two atria (right and left) hold the blood returning to the heart, and at just the right moment empty into the right and left ventricles. 

The four heart valves (tricuspid, pulmonary, mitral and aortic) keep the blood moving in the right direction through the heart.

It is helpful to visualize the heart functioning as two separate pumps, working in series; the right heart pump, and the left heart pump. 

The Right Heart Pump

The right heart pump consists of the right atrium, tricuspid valve, right ventricle, pulmonic valve, and pulmonary artery.

Its job is to make sure “used” blood gets reloaded with oxygen. Oxygen-poor blood returning to the heart from the body’s tissues enters the right atrium. When the atria contract, the tricuspid valve opens and allows the blood to be pumped from the right atrium to the right ventricle. Then, when the right ventricle contracts, the tricuspid valve closes (to prevent blood from washing backwards to the right atrium), and the pulmonic valve opens — so blood is ejected from the right ventricle and out to the pulmonary artery and the lungs, where it is replenished with oxygen.

The Left Heart Pump

The left heart pump consists of the left atrium, mitral valve, left ventricle, aortic valve, and aorta. Its job is to pump oxygen-rich blood out to the body’s tissues. Blood returning to the heart from the lungs enters the left atrium. When the atria contract, the mitral valve opens and allows the blood to enter the left ventricle. When the left ventricle contracts a moment later, the mitral valve closes and the aortic valve opens. Blood is propelled out of the left ventricle, across the aortic valve, and out to the body.

The Cardiac Cycle

You may hear about a concept called the cardiac cycle. Simply, the “cardiac cycle” is a way doctors have of dividing the work of the heart into two phases — the diastolic phase and the systolic phase. 

In the diastolic phase, the two ventricles are relaxing and are being filled with blood from the two atria.

In the systolic phase, the two ventricles are contracting.

This terminology is useful in several ways. For instance, when we measure blood pressure, we are measuring the pressure in the arteries during both phases of the cardiac cycle - systolic and diastolic. So, blood pressure is reported as two numbers, such as 120/80. Here, the systolic blood pressure (the arterial pressure at the moment the ventricles are beating) is 120 mmHg, and the diastolic pressure (the pressure during ventricular relaxation) is 80 mmHg.

Also, when cardiologists talk about heart failure, they often specify whether the cardiac dysfunction primarily affects the systolic portion of cardiac function (as in dilated cardiomyopathy), or the diastolic portion (as in diastolic dysfunction). Proper treatment requires making this distinction. 

Read about the anatomy of the normal coronary arteries.


Otto CM. Textbook of Clinical Echocardiography, 4th edition, Saunders Elsevier, 2009.

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