Heart Chambers, Valves, Vessels, Wall and Conduction System

The heart is made up of four chambers. The upper two chambers are called atria (singular: atrium) and the lower two are known as ventricles.

Muscular walls, called septa or septum, divide the heart into two sides.

On the right side of the heart, the right atrium and ventricle work to pump oxygen-poor blood to the lungs.

On the left side, the left atrium and ventricle combine to pump oxygenated blood to the body.