Giraffe Neck Blood Flow

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Giraffe neck blood flow problem investigated, according to a report in ScienceNOW 16 June 2006 and Journal of Experimental Biology vol. 209, No. 13, 1 July 2006. Biologists have long speculated about how giraffes manage to keep the blood flow to their brains when their heads can be more than 2 meters (6 ft) above their hearts. One theory was that the blood flow was kept going by a siphon effect, where the flow of blood down the jugular veins helps pull blood up the carotid arteries (the main arteries to the head). The other theory was that the giraffes needed a powerful heart that could pump at a high pressure.

To test these theories a group of scientists at the University of Wyoming build a model with lengths of tubing and an electric pump. They found the siphon effect only contributed to blood flow if they used stiff tubing, but when they used flexible tubing that was more like real blood vessels they could only maintain the flow by making the pump work harder. Graham Mitchell, a zoologist who led the study, said the results explained why giraffes have a much higher blood pressure than humans, but he also thinks that a muscular cuff around the base of the jugular vein is important in regulating the flow, especially when the animal lifts its head after drinking.

Editorial Comment: In spite of a total lack of fossil evidence, evolutionists believe that giraffes spontaneously grew longer necks and natural selection enabled the longest necked specimens to survive at the expense of the shorter necked ones. Presumably the same mysterious force that elongated the neck also simultaneously strengthened the heart and blood vessels to provide the circulation needed to maintain the blood flow whatever the position of its head. The experiment described above reminds us that it takes more than just elongating the bones and other tissues in the neck to make a giraffe. It makes far more sense to believe that giraffes were designed as whole animals with the right combination of bones, muscles, heart and blood vessels, etc. needed to function as a giraffe. (Ref. bio-engineering, hydraulics, fluids)

Evidence News 19 July 2006

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