At 09:10 AM 3/25/98 +1000, you wrote:
>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??
There is no gas exchange across the wall of the airsac in any bird. The
airsacs are relatively avascular.
>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?
This is a very good question. At depth the airsacs would be compressed
considerably and presumably the sternum would not be able to make normal
respiratory movements. Nevertheless, theoretically there could be a
cycling of air between the cranial and caudal airsacs. It would be
interesting to know if penguins stay at one depth or fluctuate between depths.
>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?
IME the relative volume of the lungs is not appreciably different from
other birds of comparable size. Maybe someone else could validate this.
>There is clearly a lot about penguin respiration that I don't know.
>Any help would be most welcome.
Me to !
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Shane Raidal BVSc PhD MACVSc
Lecturer in Veterinary Pathology
Veterinary and Biomedical Sciences
Murdoch University phone: +61 8 9360 2418
Perth,WA, 6150 fax: +61 8 9310 4144
Australia
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