<prompt> Tone of the anal sphincter in maintained byNervi erigentesInferior hypogastric plexusInferior rectal nervePelvic splanchnic nerves  <response>: The anal sphincters and puborectalis are the primary muscles responsible for continence. There are two sphincters: the internal anal sphincter, and the external anal sphincter. The internal sphincter is responsible for 85 of the resting muscle tone and is involuntary. ref - BDC 6e vol2 pg413-416 