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Male Reproductive Anatomy & Physiology

The purpose of sperm production (spermatogenesis) is to create a mechanism by which a male’s chromosome can reach a female’s, located in an egg in the fallopian tube, thereby propagating life. The production of sperm starts in puberty and persists until death. The generation of mature sperm takes 72 days, the first 50 of which are spent in the testis, while the remaining time is spent maturing in the epididymis.

The testes are a pair of round organs located in the scrotal sac. Their main function is to produce sperm and testosterone. A testis about 4-5cm long, and is composed of coiled tubes, called seminiferous tubules, containing Sertoli cells and germ cells. The germ cells are immature sperm cells, which are nourished by the Sertoli cells. Leydig cells are located between the tubes, and produce testosterone, which is necessary for sperm production.

As they mature, sperm move from the testis to the epididymis, which is a coiled channel located on the top of each testicle. Sperm travel through the epididymis for as many as 14 days as they mature. From there, sperm move into the vas deferens, which leads from the scrotal sac to the seminal vesicles. In the seminal vesicles, sperm mix with fructose, which comprises most of the volume of the ejaculate. From there the sperm travel through the ejaculatory duct, which takes the sperm through the prostate and to the urethra. During ejaculation sperm is expelled through the urethra, along with secretions from the prostate and fructose from the seminal vesicles.

The entire process of sperm production takes 10-12 weeks and is regulated by hormones released from the pituitary gland in the brain. The hypothalamus releases nRH, which travels to the pituitary, from which lutenizing hormone (LH) and follicle stimulating hormone (FSH) are released. LH is key in inducing the Leydig cells’ production of testosterone within the testes. Testosterone is an essential cofactor in the production of sperm. FSH stimulates the Sertoli cells to produce growth factors that facilitate spermatogenesis.

Causes of Infertility

Both lifestyle (ex: smoking, increased alcohol consumption, and some medications) and genetic factors can result in a diminished output of sperm by the testicles by impairing normal production. Hormonal or chromosomal deficiencies, along with long-term illnesses and childhood infections (e.g. chicken pox or the mumps) can also result in a decreased sperm count.

Structural problems in the male reproductive tract can also account for deficiencies in sperm count. Varicoceles, which are enlarged veins in the testicle are fairly common and have been found frequently in men struggling with fertility. Damage to the epididymides, vas deferentia, or ejaculatory duct can result in obstruction of the sperms’ journey from the testicles to the urethra, which can cause azoospermia, a condition in which the ejaculate is completely devoid of sperm.

In order to determine the causal factors of your infertility, it is necessary that you undergo a complete medical evaluation.

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