The Road the Sperm
Take: Spermatogenesis
Spermatogenesis, or sperm production, begins around puberty and
continues for the remainder of a man's life. The life of a single
sperm begins in the seminiferous tubules, inside the testicles.
In the walls of the seminiferous tubules, primordial germ cells
turn into spermatogonia, diploid cells (with 46 chromosomes each)
that are the precursors to actual sperm. The spermatogonia divide
repeatedly, via mitotic division to produce cells called primary
spermatocytes, still with 46 chromosomes. These divide again to
produce secondary spermatocytes, now with 23 chromosomes each. The
next cell division produces spermatids, which then develop into
spermatozoa, or sperm cells. These sperm cells have 23 chromosomes
each, half the number needed to initiate human development. The
other 23 chromosomes needed are contributed by the egg of a woman.
When a sperm joins with an egg, the conceptus (result of conception)
will have 46 chromosomes.
Spermatogenesis occurs continuously in a man's testicles from the
onset of puberty to the end life. A young healthy man produces several
hundred million sperm per day. Once produced, the sperm move their
way up into the epididymis by traveling through a network of tiny
ducts called rete testes. These rete testes are c-shaped structures
that converge from the back, to the epididymis, which is located
on the upper part of the testes. The coiled up, crescent-shaped
epididymis is a maturation chamber where the sperm take on nutrients
and grow for several weeks before moving on.
The final road for the sperm is the vas deferens. The vas deferens
begins at the epididymis and winds up past the pubic bone and urinary
bladder. There are two vas deferens, one coming from each testicle,
and they join at the back of the bladder. Each vas deferens joins
with one seminal vesicle, which contains fluids needed at the time
of ejaculation. Fluids from the vas deferens and seminal vesicles
will be released into the ejaculatory ducts, located within the
prostate gland. The prostate gland also secretes some of the fluids
found in the ejaculation. The fluid secreted is a milky alkaline
substance that provides a suitable living environment for sperm
and allows them to survive in the acidity of the vagina. The ejaculatory
ducts then connect to the urethra, where the sperm will be ejaculated
during orgasm by sexual intercourse, masturbation,
or even a wet dream.