During sexual intercourse, ejaculation occurs when sexual excitement reaches a climax or when local stimulation reaches a certain threshold, ejaculating semen into the vagina. In the process of ejaculation, the epididymis, vas deferens, seminal vesicles, prostate and bulbocavernosus muscle, sciatic cavernosus muscle and external urethral sphincter are involved. The discharge of semen is divided into 2 stages. The first stage discharges semen into the posterior urethra, a process mainly controlled by sympathetic nerves, whose central site is the sympathetic neurons in the T12 to L4 area; semen is ejected from the posterior urethra to the anterior urethra, which is called the second stage of ejaculation. The spermatozoa produced by the testes are fed into the epididymal duct through the pressure generated by the testicular fluid, the smooth contraction of the myoid cells in the intrinsic membrane of the varicoceles and the testicular capsule, the ciliary oscillation of the epithelial cells of the output tubule and the pressure difference caused by the absorption of the testicular fluid by the epithelium of the output tubule and the proximal part of the epididymal duct, and are temporarily stored in the caudal part of the epididymis without being innervated. It is then delivered to the proximal part of the epididymal body by the automatic rhythmic peristaltic contraction of the smooth muscle of the epididymal body. In the non-coital state, the rhythmic contraction of smooth muscle can drive the epididymal fluid and sperm from the caudal part of the epididymis into the vas deferens; when sexual intercourse occurs, the sympathetic nerve releases a large amount of norepinephrine, which accelerates the transport of sperm from the caudal part of the epididymis to the vas deferens. The vas deferens and ejaculatory ducts are the channels for transporting sperm, and the vas deferens also stores a portion of mature sperm. Under the action of norepinephrine released by sympathetic nerves, the smooth muscles of the cauda epididymis and the vas deferens and ejaculatory duct undergo coordinated, rhythmic strong contractions to drive the fluid and sperm from the cauda epididymis and vas deferens into the posterior urethra, and the vas deferens fluid is injected directly into the posterior urethra through the ejaculatory duct without first entering the seminal vesicles. Under sympathetic innervation, the smooth muscles of the seminal vesicles undergo 6 to 10 peristaltic contractions to discharge their secretions into the posterior urethra. The seminal vesicle fluid contains almost no sperm, and its discharge has the effect of flushing the urethral sperm. Sympathetic excitation also causes contraction of the smooth muscles of the prostate. The prostate fluid is prompted to discharge, the bladder sphincter also contracts, semen is discharged into the posterior urethra, and through a series of reflex actions and coordinated contractions of the perineal muscles the semen is discharged into the anterior urethra, completing the entire ejaculation.