The atrium is a hollow chamber that is part of the upper part of the heart. There are two atria and their names are denoted where they are located on the heart as right or left. Therefore, we have the left atria or right atria. It has its origins in England back in 1577 with the Latin language. The meaning is an opening or passageway. Everything medical is in Latin so if you know Latin than you have an edge on everyone else.
The main purpose is to receive blood from the body and squeeze it into the ventricles. The four chambered heart has a lot of advantages over a two chamber heart and the four chambered heart is more efficient.
The other purpose is giving the ventricles a little ‘kick’ in the cardiac cycle. The ventricles have a lot of work to do in order to get the blood to the body. It has to overcome all the pressure stored in the arteries of the entire body. In order to do that it has really ‘flexed’ its muscle so to speak.
The atria receives’ blood, right atria from the body and the left atria from the lungs, and holds it while the ventricles contracts or squeezes out the blood. Once the blood has left the ventricles the next load pours in by a pressure gradient known as diffusion. Since the ventricles are now in low pressure and the atria are now in high pressure the blood flows until it all equals out. At this point the ventricles are partially full and the atria still has blood left over. The atria then contracts to squeeze out the remainder of the blood into the ventricles and essentially overfills it. This causes the ventricles to be slightly stretched and now charged to give a powerful pump.
The atria contraction and subsequent over filling of the ventricles is known as an atrial kick and is part of the cardiac cycle that really helps with pushing the blood around the entire body. A failure in this area doesn’t cause a complete failure in the system as a failure in the ventricles would. It does, however, reduce the effectiveness of the pumping action of the heart and ultimately causes the heart to work too hard.