vas”). In this relatively minor operation, the physician makes
a small incision into the scrotum and then cuts through and
ligates (ties oﬀ) each ductus deferens. Sperm are still produced,
but they can no longer reach the body exterior. Eventually, they
deteriorate and are phagocytized. Vasectomy is simple and pro-
vides highly eﬀective birth control (close to 100%). For those
wishing to reverse that procedure, the success rate is about 50%.
is the terminal portion of the male duct system
(Figures 27.1 and 27.5). It conveys both urine and semen (at
diﬀerent times), so it serves both the urinary and reproductive
systems. Its three regions are:
, the portion surrounded by the prostate
Intermediate part of the urethra
(or membranous urethra) in
the urogenital diaphragm
, which runs through the penis and opens to
the outside at the
external urethral oriﬁce
Te spongy urethra is about 15 cm (6 inches) long and accounts
for 75% of urethral length. Its mucosa contains scattered
that secrete lubricating mucus into the lumen just
Check Your Understanding
What is the function of the erectile tissue of the penis?
Name the organs of the male duct system in order, from the
epididymis to the body exterior.
What are two functions of the stereocilia on the epididymal
Which accessory organ of the male duct system runs from
the scrotum into the abdominal cavity?
For answers, see Appendix H.
The Male Accessory Glands
Discuss the sources and functions of semen.
include the paired seminal glands and
bulbo-urethral glands and the single prostate (Figures 27.1 and
27.5). ±ogether these glands produce the bulk of
plus accessory gland secretions).
The Seminal Glands
, lie on
the posterior bladder surface. Each of these fairly large, hollow
glands is about the shape and length (5–7 cm) of a little ﬁn-
ger. However, because a seminal gland is pouched, coiled, and
folded back on itself, its uncoiled length is actually about 15 cm.
Its ﬁbrous capsule encloses a thick layer of smooth muscle that
contracts during ejaculation to empty the gland.
Te seminal gland mucosa is a secretory pseudostratiﬁed
columnar epithelium. Stored within the mucosa’s honeycomb
of crypts and blind alleys is a yellowish viscous alkaline ﬂuid
containing fructose sugar, citric acid, a coagulating enzyme
The Male Duct System
As we mentioned earlier, sperm travel from the testes to the
body exterior through a system of ducts. In order (proximal to
are the epididymis, ductus deferens,
ejaculatory duct, and urethra.
is about 3.8 cm (1.5 inches) long (Figures 27.1 and 27.3a, b). Its
, which contains the eﬀerent ductules, caps the superior
aspect of the testis. Its
are on the posterolateral
area of the testis.
Most of the epididymis consists of the highly coiled
, which has an uncoiled length of about 6 m (20
feet). Some pseudostratiﬁed epithelial cells of the duct mucosa
exhibit long, nonmotile microvilli (
). Te huge surface
area of these stereocilia allows them to absorb excess testicular
ﬂuid and to pass nutrients to the many sperm stored temporar-
ily in the lumen.
Te immature, nearly nonmotile sperm that leave the testis
are moved slowly along the duct of the epididymis through ﬂuid
that contains several kinds of antimicrobial proteins, including
defensins. As they move along its tortuous course (a trip that
takes about 20 days), the sperm gain the ability to swim.
Sperm are ejaculated from the epididymis, not the testes as
many believe. When a male is sexually stimulated and ejacu-
lates, the smooth muscle in the ducts of the epididymis con-
tracts, expelling sperm into the next segment of the duct system,
Sperm can be stored in the epididymis for several months. If
they are held longer, epithelial cells of the epididymis eventually
phagocytize them. Tis is not a problem for the man, as sperm
are generated continuously.
The Ductus Deferens and Ejaculatory Duct
er-ens; “carrying away”), or
, is about 45 cm (18 inches) long. It runs upward
as part of the spermatic cord from the epididymis through the
inguinal canal into the pelvic cavity (Figure 27.1). Easily pal-
pated as it passes anterior to the pubic bone, it then loops medi-
ally over the ureter and descends along the posterior bladder
wall. Its terminus expands to form the
of the ductus
deferens and then joins with the duct of the seminal gland to
form the short
. Each ejaculatory duct enters
the prostate, and there it empties into the urethra.
Like that of the epididymis, the mucosa of the ductus def-
erens is pseudostratiﬁed epithelium. However, its muscu-
lar layer is extremely thick and the duct feels like a hard wire
when squeezed between the ﬁngertips. During ejaculation, the
smooth muscle in its walls creates strong peristaltic waves that
rapidly squeeze the sperm forward along the tract and into the
As Figure 27.3 illustrates, part of the ductus deferens lies in
the scrotal sac. Some men opt to take full responsibility for birth
control by having a
to-me; “cutting the