MALE REPRODUCTIVE ORGANS
The purpose of the organs of the male reproductive system
is to perform the following functions:
To produce, maintain, and transport sperm (the male
reproductive cells) and protective fluid (semen)
To discharge sperm within the female reproductive tract
during sex
To produce and secrete male sex hormones responsible for
maintaining the male reproductive system
Unlike the female reproductive system, most of the male
reproductive system is located outside of the body. These external structures
include the penis, scrotum, and testicles.
Penis: This is the male organ used in sexual intercourse.
It has three parts: the root, which attaches to the wall of the abdomen; the
body, or shaft; and the glans, which is the cone-shaped part at the end of the
penis. The glans, also called the head of the penis, is covered with a loose
layer of skin called foreskin. This skin is sometimes removed in a procedure
called circumcision. The opening of the urethra, the tube that transports semen
and urine, is at the tip of the penis. The penis also contains a number of
sensitive nerve endings.
The body of the penis is cylindrical in shape and
consists of three circular shaped chambers. These chambers are made up of special,
sponge-like tissue. This tissue contains thousands of large spaces that fill
with blood when the man is sexually aroused. As the penis fills with blood, it
becomes rigid and erect, which allows for penetration during sexual
intercourse. The skin of the penis is loose and elastic to accommodate changes
in penis size during an erection.
Semen, which contains sperm (reproductive cells), is
expelled (ejaculated) through the end of the penis when the man reaches sexual
climax (orgasm). When the penis is erect, the flow of urine is blocked from the
urethra, allowing only semen to be ejaculated at orgasm.
Scrotum: This is the loose pouch-like sac of skin that
hangs behind and below the penis. It contains the testicles (also called
testes), as well as many nerves and blood vessels. The scrotum acts as a
"climate control system" for the testes. For normal sperm
development, the testes must be at a temperature
slightly cooler than body temperature. Special muscles in
the wall of the scrotum allow it to contract and relax, moving the testicles
closer to the body for warmth or farther away from the body to cool the
temperature.
Testicles (testes): These are oval organs about the size
of large olives that lie in the scrotum, secured at either end by a structure
called the spermatic cord. Most men have two testes. The testes are responsible
for making testosterone, the primary male sex hormone, and for generating
sperm. Within the testes are coiled masses of tubes called seminiferous
tubules. These tubes are responsible for producing sperm cells.
The internal organs of the male reproductive system, also
called accessory organs, include the following:
Epididymis: The epididymis is a long, coiled tube that
rests on the backside of each testicle. It transports and stores sperm cells
that are produced in the testes. It also is the job of the epididymis to bring
the sperm to maturity, since the sperm that emerge from the testes are immature
and incapable of fertilization. During sexual arousal, contractions force the
sperm into the vas deferens.
Vas deferens: The vas deferens is a long, muscular tube
that travels from the epididymis into the pelvic cavity, to just behind the
bladder. The vas deferens transports mature sperm to the urethra, the tube that
carries urine or sperm to outside of the body, in preparation for ejaculation.
Ejaculatory ducts: These are formed by the fusion of the
vas deferens and the seminal vesicles (see below). The ejaculatory ducts empty
into the urethra.
Urethra: The urethra is the tube that carries urine from
the bladder to outside of the body. In males, it has the additional function of
ejaculating semen when the man reaches orgasm. When the penis is erect during
sex, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated
at orgasm.
Seminal vesicles: The seminal vesicles are sac-like
pouches that attach to the vas deferens near the base of the bladder. The
seminal vesicles produce a sugar-rich fluid (fructose) that provides sperm with
a source of energy to help them move. The fluid of the seminal vesicles makes
up most of the volume of a man's ejaculatory fluid, or ejaculate.
Prostate gland: The prostate gland is a walnut-sized
structure that is located below the urinary bladder in front of the rectum. The
prostate gland contributes additional fluid to the ejaculate. Prostate fluids
also help to nourish the sperm. The urethra, which carries the ejaculate to be
expelled during orgasm, runs through the center of the prostate gland.
Bulbourethral glands: Also called Cowper's glands, these
are pea-sized structures located on the sides of the urethra just below the
prostate gland. These glands produce a clear, slippery fluid that empties
directly into the urethra. This fluid serves to lubricate the urethra and to
neutralize any acidity that may be present due to residual drops of urine in
the urethra.
How Does the Male Reproductive System Function?
The entire male reproductive system is dependent on
hormones, which are chemicals that regulate the activity of many different
types of cells or organs. The primary hormones involved in the male
reproductive system are follicle-stimulating hormone, luteinizing hormone, and
testosterone.
Follicle-stimulating hormone is necessary for sperm
production (spermatogenesis), and luteinizing hormone stimulates the production
of testosterone, which is also needed to make sperm. Testosterone is
responsible for the development of male characteristics, including muscle mass
and strength, fat distribution, bone mass, facial hair growth, voice change,
and sex drive.
