The small circulation allows the blood to obtain oxygen, and the oxygenated blood flows from the left atrium to the left ventricle.
Then it is pumped out from the left ventricle into the aorta, travels through the arteries to the whole body, transports oxygen to all the cells, and after completing its task, the blood is collected through the veins to the vena cava and finally returns to the right atrium.
At this point, the blood is lacking oxygen, so it flows from the right atrium to the right ventricle and begins the small circulation again to obtain oxygen—thus cycling back and forth, life continues unceasingly.
The heart relies on its rhythmic contraction and relaxation, pumping out and receiving blood, to achieve a continuous cycle.
There are active valves between each chamber to ensure that the blood flows in one direction only.
