Cardiovascular Function: Anatomy
The heart muscle pumps blood through the circulatory system. Each day, the heart beats 100,000 times and pumps 2000 gal of blood. The heart is composed of 4 chambers (divisions): the upper two, the right and left atria; the lower two, the right and left ventricles. Blood is pumped through the chambers, in only 1 direction, via 4 valves: the tricuspid, located between the right atrium and the right ventricle; the pulmonary, between the right ventricle and the pulmonary artery; the mitral, between the left atrium and the left ventricle; and the aortic, between the left ventricle and the aorta. Dark blood, low in oxygen, returns from body tissues through veins, enters the right atrium, and then flows to the right ventricle, the pulmonary artery, and the lungs, where it is oxygenated. Blood returns by pulmonary veins to the left atrium and goes through the mitral valve into the left ventricle, which pumps oxygen-rich, bright-red blood through the aortic valve into the aorta and then into the circulation.