The blood circulatory system, also known as the cardiovascular system, assists to deliver nutrients and oxygen to all cells in the body. Blood comes into the right atrium of the heart, from the body and moves into the right ventricle chamber. The blood is then transported into the pulmonary arteries of the lungs. After collecting oxygen, the blood travels back into the heart through the pulmonary veins and into the left atrium, then moves to the left ventricle chamber and out to the body's tissues, via the aorta of the heart.