Page 459 - Anatomy and Physiology of Farm Animals, 8th Edition

444 / Anatomy and Physiology of Farm Animals

VetBooks.ir Interstitial
tissue

Seminiferous
tubules

Figure 24-3. Seminiferous tubules surrounded by interstitial tissue. Source: Reece, 2015. Reproduced
with permission of John Wiley & Sons, Inc.

and 25). Sustentacular cells (Sertoli cells) before they are capable of fertilizing ova. The
within the seminiferous tubules envelop epididymis is arbitrarily divided into a head
developing spermatozoa and their precur- (into which the efferent ductules empty), a
sors. The sustentacular cells nourish the body lying on the long axis of the testis, and a
developing sperm and mediate the effects of tail that is attached by ligaments directly to
the gonadotropin follicle‐stimulating hor- the testis and to the adjacent vaginal tunic.
mone (FSH) and testosterone on the devel- The duct of the epididymal tail continues as
oping germ cells (Figs. 24‐3, 24‐4, and 24‐5). the ductus deferens, which conveys sperm
from the testis to the proximal portion of the
urethra within the pelvic canal.
Epididymis

The epididymis is composed of the long, Ductus Deferens
convoluted epididymal duct that connects
the efferent ductules of the testis with the The ductus deferens (formerly vas defer-
ductus deferens. It appears as a firm, arcing ens) is a muscular tube that undergoes
appendage on one side of the testis along its peristaltic contractions during ejaculation,
long axis. The epididymis houses the sper- propelling the spermatozoa from the
matozoa as they mature before they are epididymis to the urethra. The ductus def-
expelled by ejaculation. Spermatozoa are erens leaves the tail of the epididymis,
immature when they leave the testis and passes through the inguinal canal as a
must undergo a period of maturation (usu- part of the spermatic cord, and within the
ally 10 to 15 days) within the epididymis abdomen returns caudad, separating from