Importance of Hormones - Male
development of normal, mature sperm is the key to male
fertility. Sperm production is primarily regulated by two
Under the influence of testosterone and other hormones,
immature sperm cells develop through several stages and
eventually become mature sperm cells, called spermatozoa.
Spermatozoa then pass through the epididymis, where, after
18 to 24 hours, they gain motility, or movement. Finally,
mature sperm move through the vas deferens and are stored in
the epididymis until ejaculation. The complete process takes
about 72 days.
- FSH: is responsible for stimulating sperm production in the testicles
- LH: stimulates the production of testosterone, the hormone that helps maintain male sexual characteristics
When a man ejaculates (or expels the fluid from his penis),
sperm from the seminal vesicles combine with a thick fluid
from the prostate and other glands to create semen. This
fluid can be deposited into a woman's vagina, where it
travels through the cervix and uterus to fertilize an egg.
Men produce sperm from germ cells within the testes
throughout adult life. The production is controlled by
various hormones, including FSH and LH (see illustrations
2). LH stimulates the specialised Leydig cells in the testes
to secrete the male hormone testosterone. FSH, in
conjunction with testosterone, stimulates the seminiferous
tubules in the testes to produce mature sperm (see
illustration 3). Completion of the entire process of sperm
production (spermatogenesis) takes about 72 days.
highly specialized cells, which comprise two essential
parts: the head, formed by the acrosome, and the tail, which
enables the movement. The acrosome surrounds the nucleus
where genetic information is stored (see illustration 5).
The production of sperm is, however, an inefficient and
vulnerable process and for the daily production of several
hundred million mature sperm, more than eight times as many
germ cells are required. Furthermore, only a fraction of the
sperm produced will have fertilizing potential.
Sperm can live in the genital tract up to 48 hours or even
longer. The most motile sperm will progress through the
uterus and the fallopian tubes, where fertilization occurs.
Only several hundred sperm will succeed in reaching the egg
(oocyte). After the fusion of one sperm within the egg, cell
division will begin. Six or seven days after ovulation, the
embryo will implant in the uterus (see illustration 4).
depends upon such a complex array of mechanisms that it is
surprising that it is ever successful. However, failures in
fertilization may not always stem from a failed interaction
between the egg and the sperm. The problems can begin long