Glossary of Terms

Atria / Atrium
The collecting chambers for blood brought into the heart from the vena cava and from the lungs. The human heart has two atria, called the left atrium and right atrium. The right atrium receives deoxygenated blood (blood that no longer contains oxygen) from from the vena cava, then sends that blood to the right ventricle, which then pumps the blood to the lungs to receive oxygen. The left atrium receives oxygenated blood (blood that contains oxygen) from the lungs, then sends the blood to the left ventricle, which in turn pumps the oxygenated blood to the aorta, which sends the blood to the rest of the body.

Related links:
Patient's Guide to Heart Surgery: Circulation of blood