The nasopharynx, the cavity just above your mouth and behind your nose, contains a myriad of features that require naming in anatomy exams. The Eustachian tube connects the back of the nasopharynx with your middle ear. This guy is famous because opening it, by swallowing or building up pressure in the nasopharynx, equalises pressure in your middle ear and alleviates that unpleasant sensation you get in your ears when flying.
However there is another tube that connects your nasopharynx with your lacrimal sac (= collecting bag of eye tears). This nasolacrimal duct is designed to only flow one-way, from eyes to nose, and contributes to the mega-attractive runny nose when you cry. However the two valves at either end of this duct, Hasner's & Rosenmuller's, are not that sturdy. Therefore if you build up serious pressure in the nasopharnyx, the flow can be reversed.
I wanted to talk about these valves for two reasons. Firstly it's amazing what scientists/doctors will put their name on, although having said that I would jump at the chance to be immortalised in some small diverticulum or recess. Secondly, and much more interestingly, I once saw a man in the throngs of hyperemesis (= uber-vomiting) generate sufficient pressure to fill his nasopharynx and overturn Hasner & Rosenmuller's best efforts. Impressive, sort of.
A detailed diagram. N.B. tears are not red, I had merely already used my blue pen. This anatomy stuff is difficult.
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