How the Heart Works
What does the heart do?
The heart is a muscle that pumps blood. It has four chambers that take oxygen-poor blood from the body, circulate it through the lungs and pump oxygen-rich blood back into the body.
The heart’s pumping action maintains the pressure and flow of oxygenated blood throughout the entire body.
The heart has a built-in electrical system that powers this pumping action. Electrical impulses travel down a special pathway through the heart muscle and give it the power to contract (squeeze) and relax. The heart pumps (beats) about 100,000 times each day.
For infants and children, the heart is about the size of their fist. For adults, the heart is about the size of two fists.
The heart is located in the center of the chest, between the lungs. It is divided into four chambers — two on the right and two on the left, separated by a wall called the septum.
Both sides of the heart work together. The right side pumps blood into the lungs and the left side pumps blood into the organs and tissues of the body.
Each side of the heart has an upper and a lower section. The upper section (atrium) receives blood and pumps it through a one-way valve into the lower section (ventricle), which pumps it out.
The valves prevent the blood from flowing backward inside the heart. The sound of the heartbeat is made by the heart valves as they open and close.
The right side of the heart receives oxygen-poor blood from the body and pumps it to the lungs, where oxygen is added. This oxygen-rich blood leaves the lungs and enters the left side of the heart through special blood vessels called the pulmonary veins.
The heart pumps the blood into the aorta, which is the largest artery in the body — about the diameter of a garden hose. The aorta distributes the blood throughout the body to provide oxygen and nutrients for normal body functions.
As the body absorbs oxygen from the blood, the now oxygen-poor blood returns to the right side of the heart and the cycle continues. Blood circulates through the body three times every minute.
Learn more about the heart.