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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