Remember back in grade school sitting at the lunch table when someone cracked a joke just after you took a swig of milk? As you laughed milk spurted out your nose and sprayed everyone around you. Now that's entertainment. But why does this happen?
Here's how it works. In our head we have nasal passages, which allow air to go to our lungs, and an oral cavity, through which air also gets to the lungs, and food and drink get to the stomach.
These spaces are separated by the hard and soft palates, located on the top part of the mouth and throat. The hard palate has a bony plate and is near the front of the mouth. As the palate continues towards the back of the mouth muscle replaces bone, creating a softer area.
Hanging from the end of the soft palate is the uvula, the thing at the back of your throat that looks like a miniature punching bag. When we breathe with our mouths closed, air enters the nostrils and passes over the soft palate and uvula on its way to the lungs. As this happens, the uvula hangs down.
But when we're eating, drinking and swallowing, a reflex causes the soft palate and uvula to elevate and close off the nasal opening at the back of the throat so that what we're swallowing doesn't go up our nose.
Laughing causes us to exhale, which means that the soft palate and uvula drop into their breathing position. So if you laugh while drinking, the liquid shoots up into your unsealed nasal passage and out your nostrils.