Functions of the Male Reproductive System
Themalereproductivesystemhastwomainfunctions: producingspermandsecretingtestos-
terone. Spermare male gametes. Gametes were introduced in the Cell Division, Repro-
duction, and DNAchapter. Gametes are sex cells that may unite to form a new organism.
Sperm form when certain cells in the male reproductive system divide by meiosis. Mature
males produce millions of sperm each day.
Testosteroneisthemainsexhormoneinmales. YoureadabouthormonesintheControlling
the Bodychapter. Hormones are chemicals that control many body processes. Testosterone
has two major roles.
- During the teen years, testosterone causes the reproductive organs to mature. It also
causes other male traits to develop. For example, it causes hair to grow on the face. - During adulthood, testosterone is needed for a man to produce sperm.
Testosteroneisnottheonlysexhormonethatmalessecrete. Malesalsosecretesmallamounts
of estrogen, the main female sex hormone. Scientists think that estrogen is needed for normal
sperm production in males.
Male Reproductive Organs
The male reproductive organs include the penis, testes, and epididymis. These organs are
shown inFigure22.1. The figure also shows other parts of the male reproductive system.
Thepenisis a cylinder-shaped organ. It contains the urethra. The urethra is a tube that
carries urine out of the body. The role of the urethra in reproduction is to carry sperm out
of the body.
The twotestes(singular, testis) are egg-shaped organs. They produce sperm and secrete
testosterone. The testes are contained in the scrotum. As you can see fromFigure22.1,
the scrotum is a sac that hangs down outside the body. The scrotum also contains the
epididymis.
Theepididymisis a tube that is about 6 meters (20 feet) long in adults. It is tightly coiled,
so it fits inside the scrotum. It rests on top of the testes. The epididymis is where sperm
mature. The epididymis also stores sperm until they leave the body.
Other parts of the male reproductive system include the vas deferens and prostate gland.
Both of these structures are shown inFigure22.1. The vas deferens is a tube that carries
sperm from the epididymis to the urethra. The prostate gland secretes a fluid that mixes
with sperm to help form semen. Semenis a milky liquid that passes through the urethra
and out of the body.