Rectal Nerve Innervation: Anatomy and Function

Primary Nerve Supply

The rectum receives innervation from the sacral spinal cord (S2–S4) via:

• Pudendal Nerve (somatic) – From sacral plexus; controls external anal sphincter (voluntary continence), provides perianal sensation.
• Pelvic Splanchnic Nerves (parasympathetic, S2–S4) – Promote rectal contraction, relaxation of internal sphincter, defecation reflex.
• Inferior Rectal Nerves (branch of pudendal) – Sensory to anal canal, motor to external sphincter.
• Superior/Inferior Hypogastric Plexuses (sympathetic) – Inhibit emptying, maintain tone.

Functional Integration

Coordinated activity allows storage (sympathetic tone) and controlled evacuation (parasympathetic-driven contraction + voluntary sphincter relaxation). Disruption causes incontinence or constipation.