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Re: choana [was SOME SVP TIDBITS]



King, Norm wrote

>I had to ask several people, some of whom know a bit of anatomy and are 
>involved in our premed and predental programs.  They generally never 
>heard the term.  Our resident herpetologist and chordate phylogenist (is 
>that a word?) finally came to the rescue.  It turns out there are two 
>definitions.
>
>One is that the choana is the passageway by which animals get air into 
>the mouth/throat while keeping the mouth closed.  It appeared first among 
>sarcopterygians, and sarcopertygians plus tetrapods are "choanates".  It 
>includes everything from the external nostrils to the internal nostrils 
>(nares, if we're just talking about holes through the bone), or from the 
>external nostrils to the back of a secondary palate, for animals that 
>have one.  It is the whole passageway; there is no special name for the 
>passage between the primary and secondary palate.
>
>As you can see, this is not quite synonymous with internal nostril 
>(naris).  
>
>The other definition is that it is the same thing as internal nostril.  
>Of course, if you have a choana, then you also have an internal nostril, 
>and vice versa.
>
>I suspect that the first definition was the original one.  Otherwise, why 
>have a separate word?  Then, through use (misuse?), it came to also mean 
>internal nostril.  I'm speculating.
>
>
>Anyway, now I feel better.  Thank you, Norm.
>

>From The New Shorter Oxford English Dictionary (page 391)

Choana (pleural -nae) : A funnel shaped openning, specially either of those
connecting the nasal cavities to the pharynx.

Etymology : Greek khoene = funnel.

Same meaning is given also in The Penguin Dictionary of Biology & Oxford
Concise Dictionary of Zoology.

According to the above choana is the naso-pharyngeal openning (internal
naris), not the whole nasal passage.

Black's Medical Dictionary does not mention the term.

Gautam Majumdar                 gautam@majumdar.demon.co.uk