Differentiation of the accessory
sex glands:
The accessory sexual glands originate
from two epithelial tissues. They either come from the epithelial mesodermal
origin of the mesonephric duct (Wolff) or from the epithelial endodermal
origin of the urogenital sinus.
The seminal vesicle differentiates itself during the 12th week from a protrusion on the
deferent duct, near where it opens at the back wall of the urogenital sinus
(future prostatic part of the urethra). They thus have a mesodermal origin.
These paired glands produce a viscous, fructose-rich secretion that serves as a
source of energy for the sperm cells. The portion of the mesonephric duct that
lies between the junction of the seminal vesicle and the prostatic part of the
urethra is called the ejaculatory duct. Between the two ejaculatory duct
junctions the prostatic utricle (remainder of the paramesonephric duct) has its
opening. This location is called the seminal colliculus.
The
prostate develops from a
protrusion on the dorsal wall of the prostatic part of the urethra during the
12th week. The prostate's glandular epithelium develops, therefore, from cells
that have their origin in the endoderm, while the stroma and smooth muscle
develops from cells with a mesodermal origin - under the inducing influence of
DHT (see: hormonal factors in sex differentiation). The glands become active
after the 15th week and surround the two ejaculatory ducts and the prostatic
utricle as well as the prostatic part of the urethra.
Over the course of
the 12th week and parallel to the development of the prostate, bulbourethral
(Cowper's) and urethral (Littre's) glands form, originating in pairs of
endodermal protrusions of the spongy part of the urethra, which follow from the
prostatic membranous parts. Finally, the seminal fluid is augmented by
secretions from the seminal vesicle, the prostate, the bulbourethral and
urethral glands.