The cardiovascular system is comprised of the heart and the blood vessels which would extend a length of over 150,000 km. Blood circulates in two separate loops, the systemic blood stream and the pulmonary blood stream. The heart's right ventricle propels the blood to the lungs where it is oxygenated and sent back to the heart through the pulmonary veins. The blood is then expelled by the left ventricle and enters the systemic blood system which irrigates the entire body and supplies the tissues with oxygen. When the blood returns to the heart less than a minute later, it is loaded with carbon dioxide and is darker in color.

Originally released by QA International, 2005. Streaming video file encoded with permission for digital streaming by Infobase on May 06, 2015.

Cardiovascular System, The (1:00); .