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respiratory turbinates and human water loss



As per my previous warning, below you'll find another message
forwarded from Terry.  As I mentioned last month, I did not forward
all messages on dinosaur energetics to him.  However, I did forward to
him a message written by Gautam Majumdar.  If you'd like to see the
full text of that article, it can be found at:

http://www.cmnh.org/fun/dinosaur-archive/1996Dec/0313.html

I'll excerpt here in case you want some context but don't want to go
and see the whole message:

>>>Terry D. Jones wrote:

>>No--RTs ARE causally and functionally linked to endothermy unlike
>>erect limb posture, etc.  W. J. Hillenius has already shown that if
>>you bypass the RTs in a mammal, the amount of respiratory water loss
>>would through the daily water flux out of balance.  Current work in
>>our lab show the same for birds.
>
>This is certainly not true for at least one mammal - human. Average adult
>human breaths about 10,000 litres of air a day which is moistened by about
>750 ml of water. Of that only about 150 ml is saved and the rest (80%) is lost
>in the exhaled air (normal turnover of water in humans is >3 litres/day).
>Turbinectomy (surgical removal of the inferior turbinates) does not alter water
>balance to any significant extent.

Date: Fri, 3 Jan 1997 13:32:52 -0800
To: "Mickey P. Rowe" <mrowe@indiana.edu>
From: jonest@ava.bcc.orst.edu (Terry D. Jones)
Subject: Re: [gautam@majumdar.demon.co.uk: Re: Fw: [GSP1954@aol.com: MORE 
DINOSAUR ENERGETICS]]

According to our data, and that of others, the savings is 30-40% in humans
(not 20%).  Regardless, however, the cross sectional area of the nasal
passage in humans is similar to that of other extant endotherms.  The narrow
nasal passage of dinosaurs would not allow even reduced RTs since they would
significantly  increase resistance to airflow.  The fact that the passage is
narrow in the dinosaurs we studied infers that they must have had low lung
ventilation rates and therefore low oxygen consumption and hence low resting
metabolic rates.

In all endotherms we have seen the trachea is the narrowest portion of the
respiratory tract.  This is reasonable since there are no RTs or RT-like
structures there (the nasal passage is wider than the trachea in order to
accommodate both increased airflow AND the presence of RTs).  We are
currently measuring the x.s. area of the trachea in endotherms and
ectotherms and should be completed with the project in the next month or
two.  As far as I know there is currently no estimate of tracheal diameter
in dinosaurs.

TDJ
:-{)
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    Terry D. Jones                             Voice:  541/737-6120       |
    Oregon State University              Fax:      541/737-0501          
    Dept. of Zoology                         JONEST@bcc.orst.edu
    3029 Cordley Hall
    Corvallis, OR  97331-2914
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