system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the body bring tears to your eyes when choking? What is the practical purpose?
gpt
The choking reflex helps us survive, and as such it overdoes it from time-to-time, like our Flight/Fight/Freeze instinct does.

First, it triggers coughing and mouth/throat secretions for lubrication. The secretory motor system, as a byproduct, brings tears to your eyes. It's flushing everything it can as fast as it can to get whatever is blocking your airway to dislodge.

The coughing thing isn't even a regular cough, it's a super-violent kind of cough that actually sends air up into your tear ducts, which A) hurts like a mother and B) causes more tears.

Normally this wouldn't be a big problem, happens all the time. We've got a neat little system in our tear ducts has these plugs (punctum) that stop the air from coming up and lets the tears we normally produce to wet our eyes drain down into our noses.

But the sheer violence of the choking reflex shoots up so much pressure that it reverses the whole system, making the tears coming down our noses shoot back up. More tears.