Sep 1, - External hemorrhoids develop in the anus, internal hemorrhoids in the rectum. A pair of muscles called sphincters circle the anus. They relax and contract to open or close the passageway. The upper internal sphincter does its job automatically, but the lower external sphincter is under conscious voluntary control. I think I've developed hemorrhoids as a consequence of anal sex. to pop through either internally (internal hemorrhoids) or externally (external hemorrhoids).