A patient with external hemorrhoids develops pain while passing stools. Which of the following nerve mediating this pain?
External hemorrhoids are covered by the mucous membrane of the lower half of the anal canal or the skin, and they are innervated by the inferior rectal nerves. Inferior rectal nerve is a branch of pudendal nerve. Lower half of anal canal is sensitive to pain, temperature, touch, and pressure.The pectinate line indicates the level where the upper half of the anal canal joins the lower half.The mucous membrane of the upper half is sensitive to stretch and is innervated by sensory fibers that ascend through the hypogastric plexuses.The involuntary internal sphincter is supplied by sympathetic fibers from the inferior hypogastric plexuses.The voluntary external sphincter is supplied by the inferior rectal nerve, a branch of the pudendal nerve and the perineal branch of the fouh sacral nerve. Ref: Clinical Anatomy By Regions By Richard S. Snell, Page 394
Pudendal nerve
Hypogastric nerve
Sympathetic plexus
Splanchnic visceral nerve