Considering cardiovascular circulation which happens first 1-From the left atrium, the blood flows through the biscupid, or mitral valve into the left ventricle.
2- From the right ventricle, the blood flows through the pulmonic valve into the pulmonary artery.

Cardiovascular circulation happen in the following order;

Explanation:

The cardiovascular system functions by maintaining blood flow in all parts of the body. The cardiovascular system has three main components which are the heart, the blood vessels and the blood.

With cardiovascular circulation, the the right atrium pumps blood into the right ventricle and then the right ventricle pumps blood into the pulmonic valve and into the pulmonary artery. After which the blood flows to the lungs.

From the lungs, blood flows into the left atrium after which it flows into the left ventricle. The left ventricle goes on to pump the blood into the aorta and then the blood gets circulated to other parts of the body via the arteries

well when looking at this if you think about it   negativley and positivley   react with each other and when the first layer gets full they add layers it starts with 2 on the first layer and it constantly goes on until the official number is there