Development of Branched Structures and the Cellular Response to Hypoxia: An Evolutionary Perspective

Oxygenation of tissues in terrestrial vertebrates is achieved through the coordinated function of the respiratory and circulatory systems. The respiratory system fulfills an active ventilatory role in which the lungs force renewal of the air that contacts the alveolar epithelium and is juxtaposed to a dense blood capillary plexus. At this interphase, hemoglobin present in red blood cells releases carbon dioxide to the lungs and is loaded with oxygen. Thus, hemoglobin carries oxygen through very long distances with high efficiency, delivering it to the tissues and organs of the body.