system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the need to have a bowel movement sometimes pass if we don’t choose to sit on the toilet at that very moment?
gpt
The need for a bowel movement happens when stool passes into your rectum. This is a chamber just above your anus. When the rectum is stretched, because stool is inside, you get the urge to poo. However, if it's not a suitable time to do it, it would not make much sense for us to have the constant need to go. So we have evolved in a way that if we don't go within a certain amount of time, the stool is pushed backwards into your colon again and your body will try again later.