Page 463 - Anatomy and Physiology of Farm Animals, 8th Edition

448 / Anatomy and Physiology of Farm Animals

scrotum, with which it blends (Figs. 24‐7 connecting the visceral and parietal layers
of the vaginal tunic, just as mesentery
and 24‐8). The testis itself is invested with
VetBooks.ir a second layer, the visceral layer of connects parietal and visceral layers of
abdominal peritoneum; it gives off an addi-
the vaginal tunic. The mesorchium is a
delicate double layer of peritoneum tional reflection of serosa, the mesoductus
deferens that surrounds the ductus defer-
ens within the spermatic cord (Fig. 24‐9).
A testis that fails to descend into the
scrotum is called a cryptorchid testis,
and the animal with such a condition is
called a cryptorchid (Greek crypt, hid-
den; orcho, testicle). In most species, the
testes descend into the scrotum by birth
or shortly thereafter. An animal in
which the testis descends into the ingui-
nal canal but not into the scrotum is
called a “high flanker.” A cryptorchid
with both testes retained in the abdomi-
nal cavity is likely to be sterile, since
Figure 24-8. Testicle of a normal newborn goat, spermatogenesis does not occur nor-
descended completely into the scrotum. The mally unless the testis is cooler than
gubernaculum is present between the tail of the core body temperature, a condition pro-
epididymis in the distal part of the vaginal cavity
during testicular descent but it is no longer mac- vided by the scrotum. However, the rel-
roscopically visible here. vc, vaginal cavity; te, tail atively high temperature of the abdomen
of the epididymis; t, testicle; he, head of the does not interfere with the production
epididymis; dd, ductus deferens; sv, spermatic of testosterone, so a bilaterally cryp-
vein coiled in the pampiniform plexus. Source: torchid male has all the behaviors and
image courtesy of Library of Reproduction Images appearance of a normal male, except
(LORI: http://lorimainsection.blogspot.ca). that no testes are evident and no normal

Testicular
artery, vein, nerve
and lymphatics

Cremaster
muscle

Visceral
layer of
the vaginal
tunic Mesorchium
Parietal
layer of
the vaginal
tunic Ductus deferens Mesoductus deferens

Figure 24-9. Cross‐section of the spermatic cord. Source: Reece, 2015. Reproduced with permission of
John Wiley & Sons, Inc.