Semen is a gray-white liquid, mainly composed of secretions from the testicles, epididymis, prostate and seminal vesicles, as well as a small amount of secretions from the urethral glands. The liquid component is called seminal plasma, which is the necessary medium for transporting sperm. Seminal vesicle secretion accounts for 60% to 70%, and prostate fluid accounts for 20% to 30%.
Sperm is the most important tangible component in semen, accounting for 5% to 10%. Sperm is gradually developed from spermatogonia in the testicles, and the entire development cycle takes about 74 days. Adult men can produce about 100 million sperm every day. Changes in physical condition, external stimuli (such as radiation, temperature), etc., can only change the quality of sperm, but not its development cycle. A set of basic data about sperm: ① The average age at which men start producing sperm: 12.5 years old, and the amount of semen produced in each ejaculation is 2 to 6 ml; ② The number of sperm contained in each ejaculation: 100 million; ③ The life span of sperm : 2.5 months (from formation to ejaculation outside the body); ④The time required for sperm and egg to meet and fertilize: 2.5 seconds.
After the sperm are produced in the seminiferous tubules of the testes, they enter the vas deferens and are finally excreted from the body through the urethra. The vas deferens consists of the epididymis, vas deferens and ejaculatory ducts. The epididymis is a slender flat organ that is attached to the back and outside of the testicles and is about 5.5 cm long. The function of the epididymis is to store the sperm produced by the testicles and allow them to continue to develop and mature. The fluid it secretes participates in the composition of semen.
Sperm can be discharged when the vas deferens contracts. The vas deferens ascends along the posterior edge of the testis, passes through the upper part of the scrotum, reaches the groin and enters the pelvic cavity, where it meets the excretory duct of the seminal vesicle behind the bladder, and then enters the ejaculatory duct after the two meet. The ejaculatory duct is a pair of very short muscular tubes, only 2 cm long. It is formed by the confluence of the seminal vesicle excretory duct and the vas deferens. Most of it is surrounded by the prostate and opens into the prostate part of the urethra. The ejaculatory ducts suddenly open only when sexual excitement reaches a certain threshold, allowing semen to be ejected through the urethra.
After the sperm matures in the seminiferous tubules, they fall off from the Sertoli cells of the testis and enter the lumen. With the rete testicular fluid secreted by the Sertoli cells, they enter the seminiferous tubules and pass through the reticular tubes of the rete testis. , enters the epididymis through the efferent tubules from the upper and posterior part of the rete testis. Sperm stay in the extremely tortuous epididymal duct for 2 to 3 weeks, and then enter the vas deferens after further maturation. Sperm migration thereafter is primarily due to contraction of the vas deferens muscles. As the vas deferens approaches the prostate, it expands to form the ampulla of the vas deferens, where mature sperm from the epididymis are temporarily stored. When sexual excitement reaches a certain level, ejaculationThe tube is opened, and seminal vesicle gland fluid and prostatic fluid are mixed into the posterior urethra. When sexual stimulation reaches a certain level, the \”ejaculation center\” is excited, the vas deferens, seminal vesicles, prostate, bulbocavernosus muscles and ischiocavernosus muscles contract rhythmically, the bladder neck sphincter is closed under the control of sympathetic nerves, and the semen flushes out the external urethral sphincter. , the sperm and seminal plasma are discharged one by one to complete the ejaculation process.
This article is provided by Baidu Reading and is excerpted from \”The Clear \”Conception\” Plan\” Author: Sun Jianqiu and Xie Yingbiao