In males: Differentiation of the canal
system in the genital organ:
The differentiation of the male sex organ
canals is influenced by the testosterone hormone that is produced from the 8th
week in the fetal testis by Leydig's interstitial cells.
Two phenomena mark the differentiation of
the canals of the internal male sex organs:
−
The atrophy of the paramesonephric duct
(Müller)
−
The development and differentiation of the
mesonephric duct (Wolff)
The mesonephric duct (Wolff) atrophies
cranially and leaves behind only the epididymal appendage as an embryonic
rudiment. On both sides the parts of the mesonephric duct, which lie across
from the testes, form the epididymis. The testis and the epididymis of both
sides are partially enveloped by the tunica vaginalis testis (serous bilaminar
membrane with a periorchium (outermost layer) and epiorchium (inner
layer). In the part of the epididymis are end the efferent ductules. They
originate from the mesonephric tubules, and so form the beginning of the
epididym. Immediately afterwards it coils tightly and finally goes into the
lower part of the epididymis (its tail) and over into the deferent duct. This
is a musculo-epithelial tube that, during ejaculation, dispatches the sperm
cells from the epididymis into the urethra.
In the male fetus - between the 8th and
11th week - the paramesonephric duct atrophies due to the effects of the
antimüllerian hormone (AMH), which is formed by precursors of Sertol's
supporting cells (cells that surround the primordial germ cells and come from
the primitive gonadal cords). Despite the effects of this hormone, embryonic
remnants of the paramesonephric duct remain behind in males. These are the
testicular appendage at the cranial pole of the testis and the prostatic
utricle at its caudal pole.