In a step by step format, write about the process of the blood flow as it enters the heart until it leaves the heart.

To explain how blood flow enters and leaves the heart, we need to separate the bloodstream into two processes.

The first process is called a small circulation, which is the process that allows blood to pass between the heart and lungs. In this process, venous blood, which is a blood low in oxygen, is bombarded by the right ventricle of the heart to the pulmonary artery, which allows blood to leave the heart and be distributed to the right lung and the left lung. Within the lungs, blood settles into the capillaries of the alveoli, expelling carbon dioxide and absorbing oxygen. Once oxygenated, blood is transported from the lungs to the heart, through the pulmonary vein that transfers blood to the left atrium.

The second process is called a large circulation that represents the blood flow that leaves the heart and is distributed by the cells of the body. In this process, blood already rich in oxygen is transported from the left atrium to the left ventricle. Once there, the blood will be transported to the aorta, which has the function of distributing this blood to all tissues of the body.

Upon reaching the tissues, the blood allows the tissues to absorb all the oxygen and release carbon dioxide that is absorbed by the blood, making it venous once again. After that, the blood uses the aorta to walk back to the heart, entering the right atrium and starting blood flow again.