Re: Avian respiratory systems

On Oct 18, 9:27 pm, chris thompson <chris.linthomp...@xxxxxxxxx>
wrote:
On Oct 18, 6:24 pm, r norman <r_s_norman@xxxxxxxxxxxx> wrote:

On Thu, 18 Oct 2007 11:29:01 -0700, chris thompson

<chris.linthomp...@xxxxxxxxx> wrote:
I actually thought it was a more efficient system.

I don't understand -- more than what? Bird respiration is, indeed
more efficient. It is just that the "cross-current" exchange they use
is not quite as perfect as a full "counter-current" system. But it
is still very efficient and the two other adaptations really make it

It seemed to me that a transverse current system- where the
parabronchi are at right angles to the capillaries- would result in a
transfer of a higher percentage of oxygen than a counter current
system, where the flow of air is fully opposite to the flow of blood.

From my intuition:

In a counter-current system at the incoming end (from the air's
point of view) the blood has a high concentration of oxygen,
but the incoming air has even more. At the outgoing end the
concentration of oxygen in the air is low, but that of the blood
is even lower, so diffusion takes place over the entire length of
the system with roughly equal efficiency. Most heat exchangers
work this way too.

In a cross-current system, efficiency is lower at the outgoing
end, to a degree that is not fully compensated for by the increased
efficiency on the incoming side due to the reduced average contact
time.



Chris

far more efficient than the mammalian one. But in evolution, "good
enough" is enough, you don't need "best".

A bio professor posted a response to PZ Meyers discussion of avian
respiration, relating a student being distressed that humans didn't
have more efficient systems than birds, since, in the student's words,
"mammals evolved from birds". Ouch.



Thanks. A fine explanation, as usual.

I taught this stuff for decades. I do have a bit of practice
explaining it!

It's quite a help.

Chris


.

Relevant Pages

  • Re: Electoral Rolls
    ... exchanges which could not provide normal shared service facilities. ... We were on the Rowlands Gill exchange in the Consett ... the sharer wasn't using the line, ... Incoming calls rang a bell connected ...
    (soc.genealogy.britain)
  • Re: Dont want to maintain duplicate rule sets for POP and Exchange in Entourage2004
    ... > another to handle incoming Exchange message), ... uisng only one Exchange Rule it would be possible to ... > Copy incoming messages from the Exchange Inbox the the Local Inbox, ... > then run the script to Apply Rules to Unread Messages. ...
    (microsoft.public.mac.office.entourage)
  • Permit the Caching of Incoming SMTP Messages as IPM.Note
    ... does not correct the problem on my Exchange 2003 SE. ... incoming messages to public ... creating the Incoming registry value in the following ... these registry settings on all Exchange servers that host ...
    (microsoft.public.exchange.misc)
  • Re: Permit the Caching of Incoming SMTP Messages as IPM.Note
    ... To get the hotfix I recommend that you Call ... >> Update to Permit the Caching of Incoming SMTP Messages ... >> does not correct the problem on my Exchange 2003 SE. ... >> creating the Incoming registry value in the following ...
    (microsoft.public.exchange.misc)
  • Re: A1C chart
    ... |>posted several times the conversion chart my old endo gave me. ... you might have fresh blood and the results ... |>my doctor uses my A1C as an indicator, but relys more on the graphs ... The exchange period is the usual convenient way of ...
    (alt.support.diabetes)