The inferior rectal nerve (inferior anal nerve, inferior haemorrhoidal nerve) is a nerve of the perineal region.
It supplies motor innervation to the external anal sphincter and sensation to the lower anal canal and perianal skin.
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Course
The inferior rectal nerve arises from the pudendal nerve within the pudendal canal.
It passes medially, crossing the medial wall of the pudendal canal and the ischioanal fossa – accompanied by the inferior rectal artery and vein.
At the anal canal, the inferior rectal nerve terminates as motor fibres to the external anal sphincter, as well as sensory fibres to the anal canal and perianal skin.
Fig 1
The inferior rectal nerve arises from the pudendal nerve within the pudendal canal.
Motor Supply
The inferior rectal nerve supplies somatic motor fibres to the external anal sphincter.
Fig 2- The inferior rectal nerve supplies somatic motor innervation to the external anal sphincter.
Sensory Supply
The inferior rectal neve supplies sensation to the lower half of the anal canal and the perianal skin.
In females, it may also contribute to the innervation of the lower vaginal wall.