Does anyone want to laugh as much as I do, but tears come out?

You must have had such an experience, when you saw a funny thing, heard a funny joke, or were tickled by a friend until you burst into tears. Why do you laugh because you are happy, but you laugh until you cry?

In fact, tears are not only found when you are sad or laughing. They are always secreted and flow on the surface of the eyeball. It's just that the secretion is generally small, and it also flows forward along the tiny space on the surface of the eyeball and the inside of the eyelid, so it won't be okay. Therefore, we usually don't feel its existence.

Whenever we open our eyes and close our eyes, the tears on the surface of these eyeballs will be instantly sucked into the sewer of tears, that is, nasolacrimal duct. This nasolacrimal duct is not too long, and it is the only tube that can let tears enter the nasal cavity.

As long as we laugh, the pressure in the nasal cavity will increase, and tears cannot enter the nasal cavity through the nasolacrimal duct. In addition, when we laugh, our eyelids will be closed tightly, and tears will be pushed into the nasal cavity, so tears can't get in and are constantly squeezed, so accumulated tears have to flow out.