835
CHAPTER TWENTY-TWO
Reproductive System
During the descent of a testis, a pouch of peritoneum, called the
vagi-
nal process,
moves through the inguinal canal and into the scrotum.
In about one-quarter of males, this pouch remains open, providing
a potential passageway through which a loop of intestine may be
forced by great abdominal pressure, producing an
indirect inguinal
hernia.
If the protruding intestinal loop is so tightly constricted within
the inguinal canal that its blood supply stops, the condition is called a
strangulated hernia.
Without prompt treatment, the strangulated tis-
sues may die.
Structure of the Testes
A tough, white, f
brous capsule called the
tunica albuginea
encloses each testis. Along its posterior border, the connec-
tive tissue thickens and extends into the organ, Forming a
mass called the
mediastinum testis.
±rom this structure, thin
layers oF connective tissue, called
septa,
pass into the testis
and subdivide it into about 250
lobules.
A lobule contains one to Four highly coiled, convoluted
seminiferous tubules
(sem
ı˘-niF
er-us tu
bu
¯lz), each approx-
imately 70 centimeters long when uncoiled. These tubules
course posteriorly and unite to Form a complex network oF
channels called the
rete testis
(re
te tes
tis). The rete testis is
in the mediastinum testis and gives rise to several ducts that
join a tube called the
epididymis.
The epididymis, in turn,
is coiled on the outer surFace oF the testis and continues to
become the
ductus deferens.
The seminiFerous tubules are lined with a specialized
stratiFied epithelium, which includes the
spermatogenic
cells
that give rise to the sperm cells. Other specialized cells,
called
interstitial
(in
ter-stish
al)
cells
(cells oF Leydig), lie
between the seminiFerous tubules. Interstitial cells produce
and secrete male sex hormones
(f
gs. 22.6
and
22.7)
.
The epithelial cells of the seminiferous tubules can give rise to
testicu-
lar cancer,
a common cancer in young men. In most cases, the F
rst
sign is a painless testis enlargement or a scrotal mass attached to a
testis. If a biopsy (tissue sample) reveals cancer cells, surgery is per-
formed to remove the a±
ected testis (orchiectomy). Radiation and/or
chemotherapy often prevents the cancer from recurring.
PRACTICE
7
Describe the structure of a testis.
8
Where in the testes are sperm cells produced?
9
Which cells produce male sex hormones?
Formation of Sperm Cells
The epithelium oF the seminiFerous tubules consists oF sup-
porting cells called
sustentacular cells
(Sertoli cells) and
spermatogenic cells. The sustentacular cells are columnar
and extend the Full thickness oF the epithelium From its base
wall and entering the scrotum, where it remains anchored
by the gubernaculum. Each testis carries a developing
ductus
(
vas
)
deferens,
blood vessels, and nerves. These structures
later Form parts oF the
spermatic cord
by which the testis is
suspended in the scrotum
(f
g. 22.5)
.
IF the testes Fail to descend into the scrotum, they will
not produce sperm cells because the temperature in the
abdominal cavity is too high. IF this condition, called
cryp-
toorchidism,
is leFt untreated, the cells that normally produce
sperm cells degenerate, and the male is inFertile.
PRACTICE
4
What are the primary sex organs of the male reproductive system?
5
Describe the descent of the testes.
6
What happens if the testes fail to descend into the scrotum?
FIGURE 22.5
During fetal development, each testis develops near
a kidney and then descends through an inguinal canal and enters the
scrotum, completing the journey by the eighth gestational month (
a–c
).
Testis
Rectum
Gubernaculum
Symphysis
pubis
Gubernaculum
Spermatic cord
Testis
Testis
Inguinal canal
Gubernaculum
Abdominal
wall
Lower
abdominal
cavity
Developing
penis
(a)
(b)
(c)
Peritoneum
Vaginal
process
(cavity)
Scrotum
Ductus deferens
Tunica
vaginalis
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