Tracing the Path of Sperm from Production to Ejaculation

The path of sperm can be traced from the seminiferous tubules of the testes where the sperm is produced, to the epididymis where the sperm undergoes concentration and maturation, to the ampulla of the vas deferens, to the prostatic urethra, the urethra and finally ejaculated in to the vaginal canal.

The production of sperm is the function of spermatogenesis which takes place in a series of stages within the seminiferous tubules. These stages are initiated by the process of spermatogoniogenesis, which is the process of generation of spermatogonia, followed by spermatogenensis which is the genetic differentiation that produces the necessary genetic material expressed by a specific spermatozoa and leads to the development of a spermatid. Spermatocytogennesis occurs in the third stage of spermatogenesis and which leads to the production of spermatocytes which undergo structural transformation via the process of spermiogenesis to form a mature spermatid that has the structural appearance of a mature sperm. The mature spermatid is then separated from its sertoli cell via the process of spermiation and enters the tubular lumen of the seminiferous tubules. The culmination of the stages involved in spermatogenesis may take up to 72 days.

The spermatozoa produced then proceed to the epididymis via the rete testis and the ducts of the vasa efferentia. While in the epididymis, spermatozoa undergo concentration, maturation and storage in the three segments contained within the epididymis. At the point of storage, sperms have attained full maturity, are motile and have the capacity to fertilize an ovum. The spermatozoa from the caudal epididymis (where the storage stage occurs) are then stored in the ampulla of the vas deferens where the plasma portion of ejaculate produced by the accessory sex glands is added in readiness for ejaculation during sexual intercourse.

The process of ejaculation preceded by the processes of erection and emission. Sensory stimulation triggers the production of a hormone known as acetylcholine by the parasympathetic nervous system which leads to the vasodilation of the pudential arteries and the restriction of venous flow. This vasodilation and subsequent restriction of venous return increases the rate of blood flowing in to the corpus cavernosum and the corpus spongiosum contained within the penis and reduces the amount of blood flowing out. The penis becomes engorged with blood and the turgidity thus produced by this engorgement produces and erection which is necessary for vaginal penetration and therefore the process of ejaculation.

After the erection, sympathetic stimulation of adrenaline release leads to the plasma medium of transport and the mature spermatozoa collectively known as semen passing in to the prostatic urethra and finally in to the urethra. The release of adrenaline facilitates the contraction of the smooth muscles of the ampulla, caudal epididymis and deferens ducts and these contractions propel the spermatozoa from the caudal epididymis to the urethra and lead to the completion of an emission. After the emission, the parasympathetic nervous system facilitates the contraction of the bulbo-spongiosus muscle which initiates the expulsion of semen from the urethra in to the vaginal canal and the generation of impulses that move in an upward direction. These impulses generate the sensation of orgasm. Spermatozoa that are not ejaculated undergo the process of apoptosis via cytolysis and are reabsorbed by the actions of the epididymal epithelium while spermatozoa that is stored in the caudal epididymis constitutes the last portion of the ejaculate that mostly contains spermatozoa that is in the process of degeneration.

From the discussion above, it is clear to see that the pathway of sperm in the male reproductive system is a clearly defined route and the success of spermatozoa in following the processes outlined above will determine whether the process of fertilization takes place.

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