The inside of the heart - image description

The illustration shows a cross-section of the heart from the front. It shows where tubes (blood vessels) join the heart. Arrows indicate the direction blood flows through these blood vessels, into, through and out of the heart.

Four different chambers are shown inside the heart. The two at the top of the heart are called the right atrium and left atrium. The two lower and larger chambers are called the right ventricle and left ventricle. The arrows show that blood travels into each atrium, then through flaps (called valves) and into each ventricle. The arrows then show that blood leaves the ventricles through another set of valves and away from the heart through another set of blood vessels.