I'm just wondering when I yawned, there are tears coming out from my eyes, which makes me look like I'm crying.
So my question is how does yawning give out tears?
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When you yawn, the muscles surrounding the glands which are responsible for bringing tears, i.e. the Lacrimal glands get squeezed leading to teary eyes. This is the location of Lacrimal gland (it's present at the top left corner in this image):
https://upload.wikimedia.org/wikipedia/commons/c/cf/Gray896.png
These glands actually work all the time as they've the responsibility to coat the surface of our eyes (that's the reason our eyes appear glistening). When they get squeezed, due to the tightening of facial muscles surrounding the eye, or maybe because your closing eyelids too tightly while yawning, they release a small amount of "tears" they would have otherwise used at a later moment.
Also, as a side note, there are more than one type of tears, this specific type of tears are called reflex tears. Quoting a Wikipedia article as a reference (https://en.wikipedia.org/wiki/Tears#Types):
$\ldots$ It can also occur with bright light and hot or peppery stimuli to the tongue and mouth. It is also linked with vomiting, coughing and yawning. These reflex tears attempt to wash out irritants that may have come into contact with the eye.
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3$\begingroup$ Question: it was just me that genuinely yawned by reading this question/answer, or did somebody else experience the same? I'm not implying this question/answer is boring or something like this: I yawned just by reading about yawning! We learn in ethology that yawning, as a form of communication, is contagious, but I never thought that it could be started by reading about it! $\endgroup$ – user24284 May 25 '17 at 14:44
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3$\begingroup$ @GerardoFurtado I've come across that before concept before (New Scientist article a few years back I think. Did you also know Dogs catch human yawns? $\endgroup$ – Chris H May 25 '17 at 15:00
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5$\begingroup$ Oh, yes, I used to do this to my dogs all the time. Actually, when I studied ethology in the 90s, I liked testing (non scientifically, of course, just for fun) communicative yawning with different mammals every time I could... People that saw me yawning at those animals probably thought "that one has a screw loose". $\endgroup$ – user24284 May 25 '17 at 15:05
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2$\begingroup$ I'm pretty sure I've passed on yawns to my Uromastyx before. Could have been a coincidence too though. Maybe I'll yawn at her today and see what happens. $\endgroup$ – Carcigenicate May 25 '17 at 18:07
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1$\begingroup$ @Carcigenicate Nice! However, there is some debate regarding if reptiles (including birds, which are reptiles) do perform a genuine yawn. Konrad Lorenz, for instance, a huge specialist in birds, used to say that his geese didn't truly yawn, but were simply stretching their facial muscles. Maybe the same happens with your Uromastyx, sorry for being a killjoy. $\endgroup$ – user24284 May 26 '17 at 0:01
