Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: SquarishTriangle on 28/10/2016 15:24:46
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Sometimes when I yawn, I shoot saliva out of both parotid (salivary) ducts at high speed like some sort of venomous snake. Recently, I asked my close friends about this, and so far, I have found seven friends who also do this when they yawn. So not just me!
Do other people do this? Is there a purpose for humans to suddenly eject saliva from their mouths while yawning? Or is it just an unfortunate 'side-effect' of opening ones mouth to its fully aperture?
Given that many species of venomous snakes produce their venom within modified parotid glands and eject it through the modified ducts, could this be the human version of this defense system?
Or just a weird and socially-unacceptable bodily function?
Cheers.
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Is it just that an enthusiastic yawn applies considerable pressure to the salivary ducts, squeezing out a stream of saliva?
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I have expelled saliva before (quite some distance) just by having my mouth open at just the same moment that the saliva comes out. I doubt that there is any evolutionary benefit from this, just the natural byproduct of having such tiny holes for the saliva to come out of.
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There is one respect in which a human bite is quite dangerous - in the number of microbes it carries.
Human saliva is not very effective at keeping down oral microbes. So when a human bites another human - or a human punches another human in the mouth, and gashes his hand on the teeth, the results can be nasty.
Apparently, dogs have cleaner mouths than humans, and a dog bite is less likely to become infected than a human bite.
...and maybe human microbes are more likely to be antibiotic resistant?
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There is one respect in which a human bite is quite dangerous - in the number of microbes it carries.
Human saliva is not very effective at keeping down oral microbes. So when a human bites another human - or a human punches another human in the mouth, and gashes his hand on the teeth, the results can be nasty.
Apparently, dogs have cleaner mouths than humans, and a dog bite is less likely to become infected than a human bite.
...and maybe human microbes are more likely to be antibiotic resistant?
I would say human microbes are more likely to be able to thrive in and infect humans than dog microbes. Species jumping happens but it isn't easy.
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Monitor lizards, such as the Komodo dragon have a symbiotic relationship with bacteria that live in their mouths and give them an effectively venomous bite. A dragon can bite significantly larger prey, retreat, and then follow them for a few days, until they succumb to the bacterial infection, then it's dinner time for the dragon!