Blood moves from the right atrium to the right ventricle in the heart. Oxygen-poor blood enters the right atrium, is pumped into the right ventricle, then travels to the lungs for gas exchange. Oxygen-rich blood returns to the left atrium, moves to the left ventricle, and is distributed by the aorta to the body.
In the heart, blood moves from the right atrium to the right ventricle. This process begins when oxygen-poor blood returns to the heart via the superior and inferior vena cava, filling the right atrium.
Once full, the right atrium contracts, sending blood through the tricuspid valve into the right ventricle.
During ventricular systole, the right ventricle contracts, pushing the blood through the pulmonary valve and into the pulmonary artery.
This artery leads the blood to the lungs for oxygenation within the pulmonary circulation.
After this exchange of gases, oxygen-rich blood flows back to the heart via the pulmonary veins into the left atrium.
From the left atrium, blood is pumped through the mitral valve into the left ventricle, and finally, during the contraction of the left ventricle, blood is pushed through the aortic valve into the aorta.
The aorta distributes the oxygen-rich blood to the rest of the body.
Cardiac circulation ensures that blood flow occurs in a cyclical and unidirectional manner, from atria to ventricles and then onwards to either the lungs or the rest of the body depending on whether the blood is oxygen-rich or not.