section_path: Structure/Heart/Pulmonary circulation
section_name: Pulmonary circulation
paragraph_text: Pulmonary circulation
  
  The pulmonary circulation is the part of the circulatory system in which oxygen-depleted blood is pumped away from the heart, via the pulmonary artery, to the lungs and returned, oxygenated, to the heart via the pulmonary vein.
  
  Oxygen-deprived blood from the superior and inferior vena cava enters the right atrium of the heart and flows through the tricuspid valve (right atrioventricular valve) into the right ventricle, from which it is then pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs. Gas exchange occurs in the lungs, whereby CO is released from the blood, and oxygen is absorbed. The pulmonary vein returns the now oxygen-rich blood to the left atrium.
  
  A separate circuit from the systemic circulation, the bronchial circulation supplies blood to the tissue of the larger airways of the lung.