circulation

In physiology, the vertebrate system in which blood is pumped intermittently from the heart, and flows continuously around the body (systemic circulation) or to the lungs (pulmonary circulation) and back to the heart by a network of blood vessels. By means of the systemic circulation, tissues are provided with oxygen (taken up in the lungs), nutrients (absorbed from the alimentary canal), hormones, and enzymes for controlling metabolic processes and eliminating waste products (eg carbon dioxide carried to the lungs, urea to the kidneys). The pulmonary circulation is concerned with the exchange of oxygen and carbon dioxide with the environment. In mammals and birds the circulatory system also functions in body temperature regulation.

Circulation may be used in reference to:

Circulatory system, a biological organ system whose primary function is to move substances to and from cells Circulation (fluid dynamics), the path integral around a closed curve of the fluid velocity Newspaper circulation, the average number of copies of a newspaper distributed on a day Magazine circulation, the average number of copies of a periodical distributed per edition/ volume Atmospheric circulation, the large-scale movement of air Circulation (journal), a scientific journal published by the American Heart Association Circulation (UK duo), a UK house music duo Circulation problem, a generalisation of network flow problems