Describe the location, structure, and function of the
accessory reproductive organs of the male.
(“tail”) is a copulatory organ, designed to deliver
sperm into the female reproductive tract (Figure 27.1 and
). Te penis and scrotum, which hang suspended
from the perineum, make up the external reproductive struc-
, of the male.
Te penis consists of an attached root and a free
that ends in an enlarged tip, the
. Te skin
covering the penis is loose, and when it slides distally it forms
a cuﬀ called the
, around the
glans. Frequently, the foreskin is surgically removed shortly
a±er birth, a procedure called
Interestingly, over 60% of newborn boys in the United States
are circumcised, compared to 15% in other parts of the world.
Circumcision is charged by some as being medically unneces-
sary, but its proponents cite studies showing a 60% reduction
in risk of acquiring HIV (the virus that causes AIDS), as well
as signiﬁcantly reduced risks for other reproductive system
²o understand penile anatomy, it is important to know that
its dorsal and ventral surfaces are named in reference to the
erect penis. Internally, the penis contains the spongy urethra
and three long cylindrical bodies (
) of erectile tissue,
each covered by a sheath of dense ﬁbrous connective tissue.
is a spongy network of connective tissue and
smooth muscle riddled with vascular spaces. During sexual ex-
citement, the vascular spaces ﬁll with blood, causing the penis
to enlarge and become rigid. Tis event, called
the penis to serve as a penetrating organ.
Te midventral erectile body, the
sum; “spongy body”) surrounds the urethra. It ex-
pands distally to form the glans and proximally to form the
the surrounding interstitial ﬂuid. Tus, completely diﬀerent
cell populations carry out the sperm-producing and hormone-
producing functions of the testis.
, which branch from the abdominal
aorta superior to the pelvis (see
in Figure 19.24c,
p. 732), supply the testes. Te
draining the tes-
tes arise from a network called the
pampiniform venous plexus
ĭ-form; “tendril-shaped”) that surrounds the portion
of each testicular artery within the scrotum like a climbing vine
(see Figure 27.2). Te cooler venous blood in each pampiniform
plexus absorbs heat from the arterial blood, cooling it before it
enters the testes. In this way, these plexuses help to keep the testes
at their cool homeostatic temperature.
Both divisions of the autonomic nervous system serve the
testes, and when the testes are hit forcefully, associated sensory
nerves transmit impulses that result in agonizing pain and nau-
sea. A connective tissue sheath encloses nerve ﬁbers, blood ves-
sels, and lymphatics. Collectively these structures make up the
, which passes through the inguinal canal (see
is relatively rare (aﬀecting one of
every 50,000 males), it is the most common cancer in young
men ages 15 to 35. A history of mumps or orchitis (inﬂamma-
tion of the testis) and substantial maternal exposure to envi-
ronmental toxins before birth increase the risk, but the most
important risk factor for this cancer is
scent of the testes, see p. 1057).
Every male should examine his testes regularly. Te most
common sign of testicular cancer is a painless solid mass in
the testis. If detected early, testicular cancer has an impressive
cure rate. Over 90% of cases are cured by surgical removal of
the cancerous testis (
) alone or in combination with
radiation therapy or chemotherapy.
Check Your Understanding
What are the two major functions of the testes?
Which of the tubular structures shown in Figure 27.3a are
the sperm “factories”?
Muscle activity and the pampiniform venous plexus help to
keep the temperature of the testes at homeostatic levels.
How do they do that?
For answers, see Appendix H.
The Male Perineum
um; “around the anus”) suspends
the scrotum and contains the root of the penis, and the anus.
More speciﬁcally, it is the diamond-shaped region located be-
tween the pubic symphysis anteriorly, the coccyx posteriorly,
and the ischial tuberosities laterally
of the perineum is formed by muscles described in Chapter 10
The male perineum, inferior view.