Some would say quite similar to the asshole, the anal sphincter is like a little drawstring that loosens and tightens up your asshole when things are coming in and out of it.
My grandma has shit constantly flowing out of her asshole, she must have a problem with her anal sphincter.
When you have to pee in a movie but don’t want to miss anything, and must do the following mental equation: will the amount I have to pee cause enough discomfort to diminish my attention capacity for the remainder of the movie to an extent which is greater than the amount of the movie I would miss by making a mad dash to the restroom.
I saw Satantango last night, wonderful film but by the 5th hour I had to start doing pee calculus.