circulation of the blood

the basic circulation is as follows: all the BLOOD from the body returns to the HEART via the VEINS , eventually entering the right ATRIUM through the inferior and superior venae cavae (see VENA CAVA ). This contracts and forces the blood into the right VENTRICLE , and from there it is driven to the LUNGS via the pulmonary ARTERY . In the lungs, oxygen is taken up and carbon dioxide is released, and the blood then passes into the pulmonary veins and is returned to the left atrium of the heart. Blood is forced from the left atrium into the left ventricle and from there into the AORTA . The aorta branches, giving off the various arteries that carry the blood to all different parts of the body. The blood eventually enters the fine network of arterioles and capillaries and supplies all the tissues and organs with oxygen and nutrients. It passes into the venules and veins, eventually returning to the right atrium through the vena cavae to complete the cycle.