At 09:21 25/03/98 +1100, Stephen Ambrose wrote:
>Oops! I just thought I'd clear up any potential confusion that my previous
>message may have caused.
>
>A large tidal volume is useful only during the pre- and post-dive periods
>... a large intake of oxygen prior to a dive and expiration of large stores
>of carbon dioxide upon surfacing again. However, the lungs and air-sacs can
>also hold large volumes of respiratory gases during the dive as they slowly
>diffuse across the respiratory surfaces in and out of the blood.
>
>
Do gases move across the air sac walls to any extent? My texts, which
admittedly deal with domestic birds, indicate that they don't, eg in
King & McLelland 1985 (Birds their structure & Function, p135) "The blood
supply of the walls is small so that they play no part in the gaseous
exchanges". Are penguins different??
Again in domestic birds, in normal respiration there is a movement of air
from the caudal group of air sacs (abdominal & caudal thoracic), through the
lungs, into the cranial group of air sacs (cervical, clavicular & cranial
thoracic), and finally expired via the trachea.
The air sacs act like bellows, pushing and sucking the air through the lungs.
Do penguins expire (ie lose air) while under water? If not there could hardly
be any movement of air through the lungs while underwater, due to an
increase of
pressure in the cranial air sacs and a reduction in the caudal air sacs.
Or do penguins have some completely different system of air movement?
In general, birds have lungs of much smaller volume than mammals (c. 10%)
and rely on the air sacs for gas movement. Is this also true of penguins
and other diving birds or do they have relatively larger lungs?
There is clearly a lot about penguin respiration that I don't know.
Any help would be most welcome.
Peter
Dr Peter Woodall email =
Division of Vet Pathology & Anatomy
School of Veterinary Science Phone = +61 7 3365 2300
The University of Queensland Fax = +61 7 3365 1355
Brisbane, Qld, Australia 4072 WWW = http://www.uq.edu.au/~anpwooda
"hamba phezulu" (= "go higher" in isiZulu)
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