where does right atrium pump blood when it contracts
Atrium (heart) The atrium is the upper chamber in which blood enters the heart. There are two atria in the human heart, which receive blood - the left atrium from the lungs, and the right atrium from the venous circulation. The atria receive blood, and when the heart muscle contracts, pump blood to the ventricles. All animals with a closed circulatory system include at least one atrium / auricle (humans have two atria).
Pulmonary circulation Pulmonary circulation is the movement of blood from the heart, to the lungs, and back to the heart. Deoxygenated blood leaves the heart, goes to the lungs, and then re-enters the heart; Deoxygenated blood leaves through the right ventricle through the pulmonary artery. From the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle. Blood is then pumped from the right ventricle through the pulmonary valve and into the main pulmonary artery.