Male reproductive System

The male reproductive system refers to the organs involved in sexual

function and in the production of children in men or people assigned male
at birth (AMAB). These organs are both external and internal. Together,
they make, store, and ejaculate sperm, which fertilizes eggs produced by
the female reproductive system in order to begin a pregnancy. The male
reproductive system also produces hormones such as testosterone, which
play a key role in male development.
However, those organs do not function fully until puberty. This is a period
in which a child begins the physical transformation into adulthood.
Puberty kicks off when your hypothalamus and your pituitary gland start to
produce hormones that tell your testicles to start making testosterone and
sperm. Testosterone, the main male sex hormone, is responsible for the
growth and development of your penis, testicles, and scrotum, as well as
your prostate gland and your seminal vesicles, both of which help make
semen.
Testosterone also helps with what are called secondary sex characteristics.
These include the following:
 Hair on your genitals, face, and armpits
 Muscle development
 Deepening of your voice and other vocal changes
 Growth spurts that increase your height
 Male Reproductive System Parts &
Functions

External male reproductive organs

Unlike the female reproductive system, most of the male reproductive
system is located outside of the body. These external structures include the
penis, scrotum, testicles, and epididymis.
 Penis - This is the male organ used in sexual intercourse. Your penis
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 your 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 pee, i s at the tip
of the penis. The glans of the penis also contains a number of sensitive
nerve endings.
The body of your 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 you are 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 allow
for changes in penis size during an erection.
Semen, which contains sperm (reproductive cells), is expe lled
(ejaculated) through the end of your penis when you reach sexual
climax (orgasm). When your penis is erect, the flow of pee 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 your 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 your testes. For normal sperm development, the
testes must be at a temperature slightly cooler than body
temperature. Special muscles in the wall of your scrotum allow it to
contract and relax, moving the testicles closer to your body for
warmth or farther away from the body to cool their temperature.
 Testicles (testes)- These are oval organs about the size of large olives
that lie in your scrotum, secured at either end by a structure called
the spermatic cord. Most men or people AMAB have two testes. The
testes are responsible for making testosterone, the primary male sex
hormone. They also make inhibin B (which plays a role in sperm
production), insulin-like factor 3 (which helps with the development
of the testes), Mullerian inhibiting substance hormone, or anti -
Mullerian hormone (which helps with the growth of male sexual
organs), and estradiol (which aids in sperm production).
Your testes also produce sperm. Within your testes are coiled masses
of tubes called seminiferous tubules. These tubes are responsible for
producing sperm cells.
 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.
Internal male reproductive organs
The internal organs of the male reproductive system, also called accessory
organs, include the following:
 Vas deferens - The vas deferens is a long, muscular tube that travels
from the epididymis into the pelvic cavity, to just behind your bladder.
The vas deferens transports mature sperm to the urethra, the tube
that carries pee or sperm to outside of your 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 pee from the bladder to
outside of your body. It has the additional function of ejaculating
semen at orgasm. When your penis is erect during sex, the flow of pee
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 your 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-size structure that is
located below your bladder and in front of your rectum. The prostate
gland contributes additional fluid to the ejaculate. Prostate fluids also
help to nourish your sperm. The urethra, which carries the ejaculate
to be expelled during orgasm, runs through the center of the prostate
gland. Your prostate also converts some of your testosterone into
another hormone, called dihydrotestosterone (DHT), which plays a
part in sexual development throughout your life. When you're an
 adult, for example, it's involved in both prostate growth and male
pattern baldness.
 Bulbourethral glands - Also called Cowper's glands, these are pea-size
structures located on the sides of the urethra just below your 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 remaining drops
of pee in the urethra.

Male Reproductive Hormones

The entire male reproductive system is dependent on hormones, which are

chemicals that control the activity of many different types of cells or organs.
There are two types of hormones involved in sexual function and
characteristics.
Androgens - This group of sex hormones is found in much higher levels in
men/people AMAB. The most common androgen is testosterone. It helps to
make sperm and is also responsible for the development of male
characteristics, including muscle mass and strength, fat distribution, bone
mass, facial hair growth, voice change, and sex drive.
Estrogens - These hormones occur in much higher levels in women or people
assigned female at birth. They are responsible for female growth and
reproductive development. Men also have estrogen, but in smaller
amounts. Low estrogen in men or people AMAB can cause decreased
interest in sex and added belly fat. High estrogen levels may cause
infertility, larger breasts, and poor erections
In addition to testosterone, the primary hormones involved in the male
reproductive system are follicle-stimulating hormone and luteinizing
hormone.
Follicle-stimulating hormone is necessary for sperm production
(spermatogenesis), and luteinizing hormone stimulates the production of
testosterone, which is also needed to make sperm. Both of these hormones
are made by your pituitary gland, a pea-size gland that's located in the base
of your brain.

Functions of the Male Reproductive System

The male reproductive system performs the following functions:
 Produces, maintains, and transports sperm (the male reproductive
cells) and protective fluid (semen)
 Discharges sperm during sex
 Produces and secretes male sex hormones responsible for maintaining
the male reproductive system