Page 458 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Male Reproductive System / 443

nearly horizontal, and the testes are held carrying its serosal investments with it
(discussed later).
close to the abdominal wall near the super-
VetBooks.ir ficial (external) inguinal ring. The testes of seminiferous tubules (Fig. 24‐2) sur-
Each testis consists of a mass of coiled
the bull and small ruminants are near the
sigmoid (S‐shaped) flexure of the penis; rounded by a heavy fibrous capsule called
the long axis of each testis in these species the tunica albuginea. A number of fibrous
is nearly vertical, so the ruminant scrotum septa, also called trabeculae, pass inward
is dorsoventrally elongate and pendulous. from the tunica albuginea, dividing the tes-
The testes of the boar are caudal to the sig- tis into lobules and providing a framework
moid flexure of the penis, just ventral to for support of the seminiferous tubules
the anus, a position described as perineal. and the interstitial tissue that produces the
In spite of these positional differences, steroid hormone testosterone. The semi-
the essential structure of the testes in each niferous tubules are the site of spermato-
of these species is the same. The spermatic genesis, the formation of spermatozoa.
cord, containing blood vessels, nerves, The many seminiferous tubules deliver
lymphatics, and the ductus deferens, sus- sperm into a network of tubules, the rete
pends each individual testis within the testis, which drains into the efferent duct-
scrotum. The spermatic cord and its testi- ules. The efferent ductules coalesce into a
cle are doubly invested with peritoneum, a single epididymal duct.
serosal sac referred to as the vaginal tunic The connective tissue between the semi-
(Latin vagina, sheath). This investment of niferous tubules contains the interstitial
the testis reflects the fact that the fetal tes- cells (Leydig cells). The interstitial cells
tis developed within the abdomen and secrete the male hormone testosterone
reached its scrotal position by migrating when stimulated by the gonadotropin
through the serosa‐lined abdominal cavity, luteinizing hormone (LH) (see Chapters 13

Head of epididymis
Efferent ducts

Body of epididymis
Tunica
albuginea
Rete testis

Septa
Ductus deferens
Seminiferous
tubules
Tail of
epididymis

Figure 24-2. Internal anatomy of the testis. Source: Reece, 2015. Reproduced with permission of John
Wiley & Sons, Inc.