How the Heart Works

About the Heart

The heart is one of the most important and fascinating organs in your body. The function of the heart entails the pumping of oxygenated, nutrient-rich blood throughout your body. The heart is roughly the size of a clenched fist and weighs between 10-12 ounces in men and 8 to 10 ounces in females The heart, often referred to as the engine room or powerhouse of the body, ceaselessly pumps about 2,000 gallons of life-sustaining blood to all parts of the body via the 60,000-mile-long network of blood vessels. It beats around 10,000 times a day, pumping five to six quarts of blood, and can beat up to three billion times over the average lifetime. Not only does the heart supply clean, oxygen-rich blood to the various tissues in the body, but it also removes the carbon dioxide and waste from the blood before doing so.

The organ lies in the center of the chest, slightly to the left behind the breastbone (sternum) and between the lungs, and is enclosed in a moistened chamber made up of a special kind of muscle (the cardiac muscle) and is supported all around it by the rib cage.

Anatomy and Function of the Heart

The heart is made up of four chambers: the upper two are called the atria and the lower two are referred to as the ventricles. The right atrium and right ventricle together make up the right side of the heart and the left atrium and left ventricle make up the left side of the heart. The left side of the heart beats more forcefully, which is why a person feels his or her heartbeat more on the left side of the chest. The septum, a wall of muscle, separates the left side of the heart from the right side of the heart. A double-layered sac called the pericardium encloses the heart and protects the organ by holding it tightly inside the chest. The outer layer, the parietal pericardium and the inner layer, the serous pericardium, supply pericardial fluid to the heart which lubricates the organ during contractions. The heart consists of three outer wall layers: the outermost called the epicardium (which is also the inner wall of the pericardium), the middle called the myocardium (containing the muscle that contracts), and the innermost called the endocardium (which lines the chambers of the heart). The surface of the heart contains coronary arteries, which supply oxygen-rich blood to the heart muscle itself.

On the inside of the heart, the atria and the ventricles work together by contracting and relaxing, pushing and pumping blood out of the heart. When these chambers become smaller during a contraction (produced by electrical impulses from the sinoatrial node), blood is forced out of the atria into the ventricles and then from each ventricle into large blood vessels connected to the top of the heart. During this process, the blood leaves each chamber and enters a valve. There are four heart valves: the mitral valve, tricuspid valve, aortic valve, and pulmonic valve. The mitral and tricuspid valves lie between the atria and ventricles while the aortic and pulmonic valves lie between the ventricles and major blood vessels leaving the heart.

Courtesy of Mayo Clinic

Blood Vessels

There are three main types of blood vessels: the arteries, capillaries, and veins.

Coronary arteries (on the surface of the heart) supply oxygen-rich blood to the heart that keep the heart tissue healthy and if blocked by the buildup of plaque, can contribute to coronary artery disease.

Additional Resources

To understand the circulatory system and the heart’s key role in the system, click here.

To learn more about the anatomy and function of the heart, click here to see live animation video of a 3-D heart.


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