Question

What does atrium mean?

Answer 1

The word itself means a room or a small area that you enter before a larger area.

The heart has two atria, one above each ventricle. Blood flowing back to the heart from veins is under very low pressure and goes into the atria first and then into the ventricle.

The blood first goes into the atria and then a valve (the tricuspid or the mitral) and lastly into the ventricle. Both sides of the heart do this at the same time.

The atrium contract first with their thin cardiac muscle walls. They are thin because the blood is not going very far. They push a little bit more blood into the ventricles before the ventricles contract.

The contraction of the atrium causes the pulmonary and the aortic valves to close.

There is a very slight pause and then the ventricles will contract forming the tricuspid and mitral valves shut and will force open the pulmonary and the aortic valves to open as the force form these muscles is much greater.

Blood will go into the lungs and to the body and come back once again.

The sounds of these valves slamming shut produce the familiar lubb-dubb sounds of the beating heart.

If the valves do not close tightly, blood backflow produces what we call a murmur.

https://www.youtube.com/watch?list=PLCC2DB523BA8BCB53&v=NJzJKvkWWDc