system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does diarrhea need to come out RIGHT F*CKIN' NOW, but regular poo is cool to chill for a lil bit?
gpt
Because you only get the urge to poop when the feces pushes on the internal anal sphincter. Most of the time, feces is stored in the descending portion of the large intestine, far away from the sphincter, but every once in a while, intestine muscles will push the feces into the rectum where it will push against the sphincter and you get an urge to poop. However, if you hold it and don't poop, the intestine muscles pushes the feces back into the colon, and that urge to poop passes.

However, with watery diarrhea, it pools right into the rectum, where it produces a continuous poop signal (your body think your colon is *completely full* and freaks out).