How the Heart Works

Your heart is a strong muscle about the size of your fist. It beats about 100,000 times every day, pumping blood through your body. Blood carries oxygen and nutrients to your cells and takes away waste. Your heart never takes a break. It works every second of every day of your life.

Inside the Heart

Your heart has four chambers: two on top and two on the bottom. The top chambers are called atria. They receive blood coming into the heart. The bottom chambers are called ventricles. They pump blood out of the heart. Valves between the chambers open and close to keep blood flowing in the right direction.

The Blood Loop

Blood follows a loop through your body. The right side of the heart pumps blood to the lungs to pick up oxygen. The blood returns to the left side of the heart. Then the left side pumps the oxygen-rich blood to the rest of the body. After delivering oxygen, the blood returns to the right side, and the loop starts again.

Fun Facts

• Your heart pumps about 2,000 gallons of blood every day.
• If you lined up all your blood vessels end to end, they would stretch about 60,000 miles.
• A child's heart beats faster than an adult's, about 70 to 120 times per minute.

Did You Know?

The lub-dub sound of your heartbeat is made by the heart valves closing. The lub is the valves between the atria and ventricles closing. The dub is the valves between the ventricles and arteries closing!