I don't know how it is in women, having never met one, but in men the muscles that constrict to keep urine in the bladder and feces in the colon are controlled by the same nerve impulses, meaning that it is impossible to hold in your pee while you poo, and the same is true of pooing while you pee except there you can use the buttock clench method.
Anyway today I sat down to take a dump, as I often do, with no idea that my bladder was also filling up. As I passed the pooey goodness into the toilet suddenly my penis began to spray urine right into my underpants, clustered as they were around my calves. I was left with two unpleasant choices. Either jam my sphincter closed and cut off the urine but also back up my poo in my colon, or allow my penis to continue to soak my wonderful boxer shorts with not so wonderful piss. I chose the second and then showered, but this is just an unacceptable state of affairs. I know that the EVOLUTIONISTS, cursed bastards, claim that when we were animals we didn't much care where we pissed or shat and so this has carried over to today, but I know that in fact god made it this way to test us. Well fuck you god, what kind of test involves pissing in your pants? Really.
If I had designed people I would have let them piss and shit separately with no connection between the two.
That's way 29041231 in which I would design the human body better than God did.