Nucleus of pudendal nerve

The nucleus of pudendal nerve (a.k.a. Onuf’s nucleus) refers to a group of neurons which are situated in the anterior horns of upper sacral segments of spinal cord (S2 and S3; sometimes extending into S1 spinal segment as well).

The nucleus of pudendal nerve or Onuf’s nucleus serves as the origin of pudendal nerve. From here, the efferent neurons innervate the voluntary striated muscles of pelvic and perineal regions. These include levator ani, ischiocavernosus and bulbospongiosus muscles, external urethral sphincter and external anal sphincter muscles. Through its innervation of pelvic and perineal muscles, the nucleus of pudendal nerve plays an important role in bringing about erection, urinary and fecal continence and helping in ejaculation.

The higher order afferents to the nucleus of pudendal nerve arise from various parts of the brainstem, hypothalamus and cerebral cortex. These supraspinal projections modulate the working of the nucleus to regulate the contraction of pelvic floor, adjust the abdominal pressure, and harmonize the cortical emotional state of an individual with the micturition and other basic physiological functions mentioned above.