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Desert Diary
Biology/Gotta Have Heart


Bird and mammal hearts are said to be four-chambered, and are described as double pumps, because all of the blood passes through the heart twice during a single circuit of the body. The right pump sends blood to the lungs and back to the heart; then the left heart pumps it out to the rest of the body, from which it returns once again to the heart. Separating the two circuits means that freshly oxygenated blood from the lungs has no opportunity to mix with the oxygen-depleted blood returning from the body, insuring a plentiful supply of oxygen throughout.

Although both birds and mammals have the same setup, they apparently evolved it from the three-chambered hearts of their ancestors separately. Despite their seeming similarity, there is a giveaway in their embryological development. The main artery leaving the heart in birds is derived from a different embryological vessel than that of mammals. That our two hot-blooded creatures apparently required these upgraded hearts gives real meaning to the words of the song, "You've gotta have heart".
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Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.