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How giraffes keep the pressure up

This may be of interest to those sauropodomorphiles out there:

Mitchell, G., Maloney, S. K., Mitchell, D.
Keegan, D. J. (2006). The origin of mean
arterial and jugular venous blood pressures
giraffes. J. Exp. Biol. 209, 2515-2524.

The team built a mechanical model of a giraffe's neck and head, consisting of a 1660 mm long `carotid artery' tube, a 1638 mm long collapsible `jugular' tube, a linking tube to simulate blood flow through the brain, and a pump that simulated the heart. Adjusting the relative positions of the bottoms of the carotid and jugular tubes to create a siphon, the team tested several permutations of rigid and flexible blood vessels, and found that the siphon failed to deliver sufficient pressure. However, when the team activated the pump to simulate the heart's intrinsic hydrostatic pressure, they successfully generated pressures similar to those measured in the giraffe's carotid artery. And when the team constricted the lowest portion of the jugular tube, they found that the blood pressure rose dramatically. They suggest that by constricting the jugular at this point, giraffes could maintain sufficient blood pressure, when they raise their heads after drinking, to prevent themselves from passing out.



Dann Pigdon
GIS / Archaeologist         http://heretichides.soffiles.com
Melbourne, Australia        http://www.geocities.com/dannsdinosaurs