Avian Circulatory System

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Avian Circulatory System Birds have very efficient cardiovascular systems that permit them to meet the metabolic demands of flight (and running, swimming, or diving). The cardiovascular system not only delivers oxygen to body cells (and removes metabolic wastes) but also plays an important role in maintaining a bird's body temperature. The avian circulatory system consists of a heart plus vessels that transport: * nutrients * oxygen and carbon dioxide * waste products * hormones * heat Birds, like mammals, have a 4-chambered heart (2 atria & 2 ventricles), with complete separation of oxygenated and de-oxygenated blood. The right ventricle pumps blood to the lungs, while the left ventricle pumps blood to the rest of the body. Because the left ventricle must generate greater pressure to pump blood throughout the body (in contrast to the right ventricle that pumps blood to the lungs), the walls of the left ventricle are much thicker & more muscular. Source: chickscope.beckman.uiuc.edu/explore/ embryology/day02/comparative.html | Cross-section through the ventricles of a chicken heart (Source: trc.ucdavis.edu/mjguinan/apc100/modules/ Circulatory/heart/chambers1/chambers.html) | Dorsoventral (A) and lateral (B) thoracic radiographs from a grey heron, showing the normal avian cardiac silhouettes, which are located nearly along the longitudinal axis of the body (Machida and Aohagi 2001). Birds tend to have larger hearts than mammals (relative to body size and mass). The relatively large hearts of birds may be necessary to meet the high metabolic demands of flight. Among birds, smaller birds have relatively larger hearts (again relative to body mass) than larger birds. Hummingbirds have the largest hearts (relative to body mass) of all birds, probably because hovering takes so much energy. | | | Electrical activity
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