What does the top half of heart do?

The top half of the heart is known as the atria. The atria are responsible for receiving blood from the body and lungs and pumping it into the ventricles, the bottom half of the heart.

There are two atria, the left atrium and the right atrium. The left atrium receives oxygenated blood from the lungs via the pulmonary veins, while the right atrium receives deoxygenated blood from the body via the superior and inferior vena cavae.

The atria contract in a coordinated fashion, first the right atrium and then the left atrium, to force the blood into the ventricles. The ventricles then contract to pump the blood out to the body and lungs.

The atria also play a role in regulating the heart rate and rhythm. They contain specialised cells called the sinoatrial (SA) node and the atrioventricular (AV) node, which generate the electrical impulses that cause the heart to beat.