Some dogs are born with anal canals that do not close well. (thedrakecenter.com)
This method teaches the child not to strain while keeping their anal canal open. (pottytrainingconcepts.com)
A third degree tear extends downwards from the vaginal wall and perineum to the anal sphincter, the muscle that controls the anus and a fourth degree tear extends to the anal canal as well as the rectum. (sciencedaily.com)