Page 462 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Male Reproductive System / 447

Inguinal Canal animal, the ovaries remain in the abdomi-
nal cavity near their origin; but in the male
VetBooks.ir The inguinal canal is a passage from the animal, the testes travel (descend) a consid-

erable distance from their point of origin
abdominal cavity to the exterior of the body
that extends from the deep inguinal ring to to the scrotum. The environment of the
the superficial inguinal ring (Fig. 24‐6B). scrotum features a temperature a few
The deep (internal) inguinal ring is a space degrees lower than that of the normal body
or potential space between the caudal temperature; this lower temperature is
border of the internal abdominal oblique favorable to spermatogenesis.
muscle and the deep face of the aponeurosis The descent of the testis normally is
(flat tendon) of the external abdominal complete by birth or soon after (Figs. 24‐7
oblique muscle. The superficial (external) and 24‐8). It is guided on its journey by the
inguinal ring is merely a slit in the aponeu- fibrous gubernaculum, a cordlike struc-
rosis of the external abdominal oblique ture that initially extends from the testis
muscle. In addition to the spermatic cord, through the inguinal canal to the skin in
the canal allows passage of the external the region that will become the scrotum.
pudendal artery and a sensory nerve that As the fetus grows, the gubernaculum
serves the inguinal region of the abdominal guides the testis from the abdominal cavity
wall. This accounts for the existence of the into the scrotum. The gubernaculum lacks
inguinal canal in female animals. contractile elements, so it does not in fact
The inguinal canal is normally a “pull” the testis into the scrotum. Rather,
potential space, large enough only to the rapid and dramatic growth of the fetus
permit passage of the spermatic cord ultimately displaces the tethered testis
and inguinal vessels and nerves. If the from the abdomen to its extra‐abdominal
internal inguinal ring and canal are too location.
capacious, a loop of intestine may pass The testis begins its development
through the canal into the scrotum, pro- covered (as are all abdominal organs) with
ducing an inguinal hernia. visceral peritoneum. As it descends into
the scrotum, it pushes the parietal perito-
neum ahead of it, thus acquiring a second
Descent of the Testis layer of serosa. This second outer layer of
peritoneum (the parietal layer of the vag-
In both male and female fetuses, the gonads inal tunic) is continuous with the parietal
develop in the sublumbar region immedi- peritoneum at the internal inguinal ring
ately caudal to the kidneys. In the female and lies deep to the deep fascia of the

(A) (B) (C)

Ductus
deferens Coelom
T
Coelom
Body wall Coelom T

Peritoneum T
Vaginal
Vaginal tunic
Gubernaculum process Former gubernaculum =
scrotal ligament

Figure 24-7. Descent of the testis (T). The embryonic coelom will become the abdominal and pelvic
cavities.