>>Would Steve or Shane or anyone comment on whether the one way flow
>>counter-current system of oxygen exchange in the avian lung would >be
>advantageous cf with mammalian lung structure at depths? My >guess it that
>while it is an advantageous at high altitudes to >improve oxygen absorption
>it doesn't make much difference at >depths because the air is not flowing
>through the lungs.
Pat,
Perhaps there is sufficient diffusion of gases between the lungs and the
reserve of air in the airsac system to not require air movement between the
airsacs and the counter-current pulmonary blood flow. At depths of say 200
m the air in the airsac system will be so compressed that it would probably
just fill the voume of the relatively rigid lungs and trachea. The oxygen
tension (potentially equivalent to ~ 400 kPa) would actually be rapidly
fatally toxic to humans and as Stephen pointed out before, the increased
nitrogen tension should already have caused us narcosis. So maybe the last
thing they need at depth is efficient respiration. Just a theory.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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