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Re: Sauropod necks and blood pressure



On Tue, 14 Mar 1995 17:06:17 -0500, <FEUKAC@PLU.edu> wrote:
>On Tue, 14 Mar 1995, Mikiel wrote:
>
>>  Here's a silly question I thought I'd throw out to stir up some 
>> more talk about the necks of sauropods.  Perhaps someone out there who's 
>> familiar with giraffe anatomy can answer this one.  Supposing for a 
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>>  Of course, I don't know that the heart in sauropods is situated 
>> above the level of any organ which could pool the blood (perhaps the heart 
>> itself?), but I thought I'd ask.
>> 
>> -Mikiel
>> 
>  Another log  to toss on the fire is that the blood pressures described 

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>and theories.  Ideas anyone? 
>
>Aaron Feuk
>Preparator,Dept. of Earth Sciences 
>Pacific Lutheran University
>Tacoma, Wash. 98447

Well, I have some suggestions.  You are correct 
in analyzing the "siphoning effect" -  up to a point.  There is a negative 
pressure (relative to atmospheric) in the upper veins.  However, siphoning 
requires a fairly rigid tube to work well.  Instead, veins collapse when 
blood is not flowing through them at high rates.  That is, the diameter 
matches the flow.  As to the extraordinary pressure for arterial pressure 
in sauropod necks, now that is a difficult problem.  I suspect that a low 
metabolic rate would allow for smaller blood flow rates - i.e., don't 
directly transfer mammalian factors to sauropods.  The venous muscle 
"pump" of the human body requires valves every few centimeters.  The 
pressure gradient between capillary and heart is about 10 mmHg, 
insufficient for blood movement. Muscle bulging during contraction 
collapses engorged veins moving blood to the next valve until the heart is 
reached.  A comparable system is feasible if the brain were small and 
metabolism low at sauropod neck lengths.  I don't know if it is true, but 
it is feasible.

Rich Hengst - 
rhengst@davros.cc.purduenc.edu
Master of dino breath