Neuroanatomy and physiology of ejaculation.

Ejaculation is the final stage of coitus in the mammalian male and results in the expulsion of sperm out of the urethral meatus. Two successive phases, emission and expulsion, can be distinguished during ejaculatory response. Normal anterograde ejaculation requires close coordination of sympathetic, parasympathetic, and somatic components commanding the different peripheral anatomical structures (accessory sexual glands, ducti, and striated muscles) involved in ejaculation. The efferent pathways innervating these anatomical structures drive motor outputs originating from spinal thoracolumbar and lumbosacral nuclei. These spinal ejaculatory centers, the synchronized activation of which is likely carried out by a group of spinal cells, are under the control of both peripheral sensory afferents coming from genital areas and supraspinal information arising from specific brain regions.