The heart is a muscular organ that pumps blood through the blood vessels of the circulatory system. Blood transports oxygen and nutrients to the body. It is also involved in the removal of metabolic wastes. This video describes how blood flows in and out of the heart.
Blood enters the heart through two large veins – the posterior (inferior) and the anterior (superior) vena cava – carrying deoxygenated blood from the body into the right atrium.
Blood flows from the right atrium into the right ventricle through the tricuspid valve. When the ventricle is full, the tricuspid valve shuts to prevent blood flowing backwards into the atrium.
Blood leaves the heart through the pulmonic valve into the pulmonary artery and flows to the lungs.
The pulmonary vein carries oxygen-rich blood from the lungs into the left atrium.
Blood flows from the left atrium into the left ventricle through the open mitral valve. When the ventricle is full, the mitral valve shuts to prevent blood from flowing backwards into the atrium.
Blood leaves the heart through the aortic valve into the aorta and to the rest of the body.