Blood comes into the right atrium from the body, moves into the right ventricle and is pushed into the pulmonary arteries in the lungs. After picking up oxygen, the blood travels back to the heart through the pulmonary veins into the left atrium, to the left ventricle and out to the body's tissues through the aorta.
The pumping process
The heart's blood pumping cycle, which is called the cardiac cycle, begins when oxygen-free blood returns to the heart through the right atrium, after distributing oxygen and nutrients to other parts of the body.
Circulation
Blood is carried through the body in blood vessels, or tubes, called arteries and veins. The process of moving blood through the body is called circulation. Together, the heart and vessels make up the cardiovascular system.
