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 (singular: ventricle).

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.