"At its origin the inferior rectal nerve branches from the pudendal nerve within the pudendal canal in the lateral wall of the ischioanal fossa, also travelling within this canal are the internal pudendal artery and vein. The lateral wall of the ischioanal fossa also houses the tuberosity of the ischium, the obturator internus muscle and the obturator fascia (that composes the pudendal canal). Outside the pudendal canal and crossing the lateral wall of the ischioanal fossa transversely (within the ischiorectal fat) are the paired inferior rectal arteries, which supply the inferior part of the anal canal as well as the surrounding muscles and perineal skin. Similarly, inferior to the pectinate line the internal rectal plexus drains into the inferior rectal veins around the margin of the external anal sphincter."
"The inferior rectal nerve, also known as the inferior anal nerve or inferior haemorrhoidal nerve, is a branch of the pudendal nerve which is derived from S2, S3 and S4 nerve roots of the sacral plexus. The nerve provides sensory innervation to the anal canal inferior to the pectinate line and motor innervation to the external anal sphincter."
"The branches of the inferior rectal nerve provide somatic cutaneous sensation to the anal canal inferior to the pectinate line and therefore this part of the anal canal is sensitive to pain, touch and temperature. Somatic efferent fibres from the inferior rectal nerve also stimulate contraction of the voluntary external sphincter."
"cadaveric studies have demonstrated that the inferior rectal nerve does not always enter the pudendal canal and instead may pass behind the sacrospinous ligament to enter the ischioanal fossa; dissections have also demonstrated that the inferior rectal nerve may pierce the sacrospinous ligament"