Why do your eyes tear-up after you yawn?

Just wanted to know....try not to yawn!

There r two possible explanations:

1- During a yawn, there is a slight increase in pressure inside the skull (likely caused by slight increases in the amount of oxygen taken in during a deep yawn). This causes the cerebrospinal fluid (CSF), the fluid that surrounds the brain & flows through the brain is ventricle system, to be forced out faster than normal. That fluid enters the lachrymal (tear) system. That increase in fluid pushes out the tears.

2 - the more simplistic reason may be that when u yawn u scrunch up a bunch of facial muscles. That causes the tear glands & ducts to be squished, forcing out some tears.

Yawning yet?