ANATOMY
The
male genitalia is composed of the external genitalia (on
the outside of the body) and the internal genitalia (buried
within the body). The external genitalia consists
of the penis, scrotum, and pubic hair. The internal
genitalia consists of a number of hidden glands and tubes
that play a role in the production and delivery of sperm.
These
include the epididymis (e), vas deferens (vas), and prostate
gland (pr). Other internal structures seen in the
drawing to the left are the pubic bone (PU), the urethra
(u), and the testicle (T). For the sake of brevity,
we will mostly focus on the external genitalia.
The
most obvious aspect of the external male genitalia is the
penis. The penis consists of a body (shaft) and glans
(head). Under the skin (as shown in the picture of
a dissected penis to the right) the body (B), or shaft,
of the penis contains three columns of tissue that can fill
with blood to become an erection. The corpus cavernosum
makes up the bulk of the penis tissue. At the underside
of the penis is the corpus spongiosum (S) that also can
fill with blood to form an erection. Running down
the center of the corpus spongiosum is the urethra.
The urethra is the tube which connects the bladder to the
tip of the penis and is where both urine and semen exit.
The penis is firmly attached to the pelvic bone by two strong
bands of fibrous tissue, called the root. The root
is not visible except when dissected. In this picture
of a dissected penis (looking at the underside), the skin
has been removed showing some of the underlying structures.
The roots (R) join to become the body (B).
The
tip, or head, of the penis is called the glans (G).
It is one of the most sensitive areas on a man's body, containing
many nerve fibers. Unless one is circumcised, the
glans is covered by a loose, hoodlike fold of skin called
the foreskin (f) or prepuce. This foreskin can be
pulled back exposing the glans. In those who are circumcised,
the foreskin has been surgically removed just below the
glans. There is often a wrinkle-like scar on the shaft
at the site where the foreskin was removed.
Circumcision
is a controversial procedure whereby the skin normally covering
the head of the penis is removed. It is commonly done for
religious or cultural reasons, and in the past was believed
to be medically superior to be circumcised. Recently, a
number of clinical studies have shown that although circumcised
men do have a slightly lower rate of penile cancer and bladder
infections when compared to uncircumcised men, the difference
is not significant. Most of the American medical community
today believes circumcision is not necessary. Many believe
it is downright cruel and disfiguring. For more information
on the pros and cons of circumcision, check out the American
Academy of Pediatrics policy statement on this topic.
A
circumcised and uncircumcised penis. A cross-section through
the shaft.
The
vertical slit at the tip of the glans is the urethral meatus
(m); it is the opening of the urethra (u). The urethra
is a tube-like structure through which both urine and semen
flow.
The
base of the glans is a cone shape called the corona. Around
the corona are numerous small sebaceous glands, which in
latin are called glandula Tysonii odorifera.
These glands secrete a whitish material which has a peculiar
odor; this cheese-like substance is called smegma.
The
scrotum is a loose, wrinkled pouch that has two compartments,
each of which contains a testicle. The testicles are
oval, rubbery structures that are about 4.5 cm long (range
is usually 3.5 to 5.5 cm). The left testicle usually
lies somewhat lower than the right. On the back side
of each testicle is the softer, comma-shaped, epididymis
(e); it feels somewhat like a bag of worms. Sperm
leaving the testicle (where it is made), flows through the
epididymis (e) into the vas deferens (vas), and joins the
urethra (u) in the prostate (pr).
