1 the movement of a fluid in a circular course, especially the passage of blood through the cardiovascular system.
2 the system of vessels effecting this passage. pulmonary c. circulation of blood between the heart and lungs. Deoxygenated blood passes to the lungs from the right ventricle via the pulmonary artery; oxygenated blood returns to the left atrium via the pulmonary vein. systemic c. circulation of blood between the heart and all parts of the body except the lungs. Oxygenated blood leaves the aorta and deoxygenated blood returns into the vena cava. See also collateral circulation.