How Your Heart Pumps Blood

Your heart is a muscle about the size of your fist, and it works day and night for your whole life. Its job is to pump blood around the body, delivering oxygen and nutrients to every part and carrying waste away.

Four chambers

The heart has four chambers. The two upper chambers are called atria, and the two lower chambers are called ventricles. A wall of muscle divides the heart into a right side and a left side.

Two loops

Blood travels in two loops. The right side of the heart receives blood that has already given up its oxygen, and pumps it to the lungs. In the lungs, the blood picks up fresh oxygen. That oxygen-rich blood returns to the left side of the heart, which pumps it out through the arteries to the rest of the body. After the body’s cells have taken what they need, the blood returns through the veins to the right side, and the cycle begins again.

Valves keep it one-way

Each chamber has a valve at its exit that works like a one-way door. Valves open to let blood move forward and close to stop it flowing backwards. The familiar ‘lub-dub’ sound of a heartbeat is the sound of these valves closing.

What sets the beat

A heartbeat is triggered by a tiny electrical signal that starts in a small group of cells in the heart, known as the natural pacemaker. The signal spreads through the heart in an orderly way, making the chambers squeeze in the right order. In a resting adult, the heart typically beats somewhere between about 60 and 100 times a minute. It beats faster during exercise, when the body needs more oxygen.

The heart needs blood too

The heart muscle itself needs a supply of oxygen. It gets this from its own small arteries, called the coronary arteries, which run across its surface.

Key points

• The heart is a muscular pump with four chambers.
• The right side sends blood to the lungs, and the left side sends it to the rest of the body.
• Valves keep blood flowing in one direction.
• A natural pacemaker sets the rhythm of the heartbeat.

This article is general education, not medical advice. If you are worried about your heart, please speak to a doctor.