This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen and pelvis, Subject name: Anatomy
Tone of the anal sphincter in maintained by 
Select and explain. 
A. Nervi erigentes, B. Inferior hypogastric plexus, C. Inferior rectal nerve, D. Pelvic splanchnic nerves
C: Inferior rectal nerve
Answer: C: Inferior rectal nerve 
Explanation: 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