Functional Anatomy of the Goat - Goat Science and Production - page 119

by the testicle during its descent (in the developmental
intrauterine life), and others are modifi ed skin and subcu-
taneous connective tissue, all functionally and clinically
important. The tunics brought by the testicle during its
descent are the internal spermatic fascia and the vaginal
tunic. The former is the continuation of the endoabdominal
fascia, whereas the latter is the continuation of the perito-
neum (consisting of a parietal and a visceral lamina). The
tunics outside of the body wall are the external spermatic
fascia (a connective tissue layer) and the modifi ed skin
(the scrotal skin outside and the tunica dartos inside).
While the tunica dartos makes two dartoic sacs (one
for each testicle), the scrotal skin surrounds both testicles
and their spermatic cords, all together. (See the spermatic
cord.)

The male urethra is a common excretory duct for the
urine and semen. It is divided in two segments: pelvic and
penile urethra. The pelvic urethra is a continuation of the
urinary bladder lying on the fl oor of the pelvic cavity, is
surrounded by a spongy coat and the urethralis muscle, and
suddenly narrows at the level of the ischiatic arch. Here
the pelvic urethra continues as the penile urethra, follow-
ing the urethral isthmus (the narrow part).
The annex glands are the prostate, the vesicular glands,
and the bulbo-urethral glands. Their function is to produce
seminal fl uids for nourishing the sperm and facilitate the
gliding of sperm through the excretory passages.
In the goat, the prostate is a disseminated gland com-
pletely surrounding the walls of the pelvic urethra. The
vesicular glands are paired, 3-4 cm long, with lobulated
surfaces and located on both sides of the neck of the
urinary bladder. Their ducts open on the colliculus semi-
nalis. The bulbo - urethral glands are located far caudally,
on both sides of the urethral isthmus, and are rounded and
small, 1 cm in diameter. Their excretory canals pass through
the urethra and open directly into the urethral recess, which
is illustrated in Figure 6.33B (see Figure 6.33).

T HE R EPRODUCTIVE E XCRETORY P ASSAGES
There are three reproductive excretory passages in the
male goat: the epididymis, the ductus deferens, and the
urethra with the annex glands. The function of these pas-
sages is to allow the sperm to exit and be able to fertilize
the ovules.
The epididymis is attached to the caudal border of the tes-
ticle and covered by an expansion of the albuginea. It starts
with a head, which covers the head of the testicle, continues
with a body, and ends by the tail, ventrally. From this point,
it continues vertically in a proximal direction with the ductus
deferens. The head contains many canaliculi (ductuli effer-
entes), in continuation of the rete testis. The canaliculi
connect with each other and form the ductus epididymidis,
which runs inside of the body of epididymis. This duct
becomes very fl exuous and may measure as long as 60
meters. There is a niche, the so-called testicular bursa on the
lateral side, between the testicle and the body of epididymis.
The ductus deferens is the continuation of ductus epi-
didymidis starting from the tail of the epididymis. It is a
straight duct, included within the spermatic cord, enters the
abdominal cavity, and reaches the pelvic urethra just
caudal to the neck of the urinary bladder. It empties on the
roof of the urethra apparently enlarged (ampulla) and
bearing small glands, lateral to the colliculus seminalis.
The latter is an elevation of the urethral mucosa, at the end
of the urethral crest (Figure 6.33A).
The spermatic cord consists of the ductus deferens, the
visceral lamina of the vaginal tunic, and the vessels and
nerves supplying the testicle and the epididymis. This
complex structure is subject to various surgical interven-
tions and techniques used for castration, criptorchidism,
inguinal hernia, etc. In the goat, the spermatic cords are
long, making the testicles pendulous during the walk.

T HE P ENIS
The male copulatory organ, the penis, consists of the root,
the body, and the apex. The goat has a fi broelastic penis,
still fi rm when not erect. Its function is to allow the urine
and also the sperm to be expelled. This is done by refl exes
and by contraction of some of the penile muscles. The
average length of the penis is 40 cm long. Starting from
the ischiatic arch, the penis extends cranially and passes
between the thighs ventral to the pelvis, and between the
two spermatic cords, surrounded by skin and fasciae. On
the ventral aspect of the abdominal cavity, the free part of
the penis is protected inside of the prepuce. (The free part
of the penis belongs to the body of the penis.)
The root of the penis is composed of the two crura and
between them, the bulbus penis. The crura (sing. crus) are
attached to the ischiatic arch, the very end of the coxal
bones. The crura are covered by two symmetrical muscles
that act in the erection of the penis. The bulbus penis is the
caudal expansion of the corpus spongiosum penis, which
is the erectile tissue of the penis. It is covered by a muscle.
The body of the penis consists of the paired corpus
cavernosum penis (each of them the continuation of the
corresponding crus penis), and the penile urethra sur-
rounded by the corpus spongiosum penis. The expression
“corpus cavernosum” is used for the unique structure as a
result of fusion of the paired corpus cavernosum. The
corpus cavernosum and the penile urethra with the corpus