الفهرس 
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Abstract
The present work was conducted on 99 Newzealand white
rabbits embryos and fetuses from 11—30 days of prenatal
life, as well as, 64 male rabbits aging from 5-870 days of
posnatal life. The collected specimens covered most of the
ontogenic developmental ages. Serial and step serial
sections of 4-6 micrometers thick were prepared and stained
with different histological stains.
The indifferent gonads of rabbit fetuses appeared as
bilateral thickenings on the medial face of the mesonephroi
at 11 days of age. These elevations were formed of compact
aggregations of mesenchymal cells, very similar to
mesonephric mesenchyme, as well as primitive gonadal cells
and covered by gonadal surface epithelium. The latter was
formed of crowded irregulary arranged cuboidal and/or
flattened cells lacking basal lamina.
The primitive gonadal cells were arranged into
primitive gonadal cords that appeared in contact with the
surface epithelium, while others appeared as isolated cell
masses. Such cellular organization was supported by very
fine reticular net and permeated by blood capillaries
contained immature nucleated red blood corpuscles.
First generation of primordial germ cells or gonocytes
were noticed at some sites between, under and contact with
the surface epithelial cells without any demarcation. Some
gonocytes were found among the mesenchymal cells, juxta
blood vessels, near to the mesogonadium and along the course
of the primitive gonadal cords. Some of the primitive
gonadal cells and gonocytes were seen in proper mitotic
activity. As rabbit fetuses reached 19 days of age, the
differentiation of the indifferent gonads to form fetal
testis was evidenced. The signs of the differentiation were
the formation of the primitive testicular cords and the
appearance of primitive tunica albuginea.
The primitive testicular cords appeared as densely
arranged solid cords lacking lumen. A thin PAS positive
basal lamina surrounded these cords.
These cords appeared to be formed of convoluted parts
under the tunica albuginea and straight part coursed toward
the mediastinum anlage. Primitive gonadal and gonocyte cells
formed the cellular constituents of the cords.
By 21st day, lumination of the testicular cords became
as a prominent feature in most of the cords. Moreover, the
cords became well demarcated and surrounded by flattened or
elongated curved cells, differentiated from the pericordal
mesenchyme. Such cells would form, during the post—natal
stage of development, as the myoid elements of the
testicular cords.
Within the luminated cords, the primitive gonadal
cells gave rise to the fetal indifferent supporting cells of
Sertoli, such cells were localized themselves more
peripheral than to be in the center of the cords.
By the 25th day, the cord cells were increased in
number as a result of successive mitotic activity as well
as, their migration from the interstitium through the
interrupted basement membrane.
As development proceeded and at the end of fetal
development, the gonocytes undergo degenerative changes. The
stage of gonocyte degeneration was accompaned by gonocyte
maturation and the formation of fetal prespermatogonia. The
latter had moved to the tubular periphery to be aligned
along the basal lamina inbetween the differentiated or
partially differentiated peripheral supporting cells of
Sertol i. After birth, only prespermatogonia and Sertoli cells
were present in the testicular tubules during the neonatal
stage of development. Few degenerating cells were seen
during this period. The mitotic activity was greatly
decreased or could not be noticed. Amitotic division started
and progressed gradually as development proceeded.
Spermatogenesis started at 7—8 weeks of age. The
process of Spermatogenesis was divided into different
stages; spermatogonial maturation stage (from 7—8 weks of
age) where the spermatogonia type A and B were seen
indicating the onset of spermatogenesis; Spermatocyte
maturation stage (from 9—12 weeks of age) where the
spermatocytes were first seen; spermatid maturation stage
(from 13—14 weeks of age) where all stages of
spermatogenesis were evident and spermatozoa appeared in the
tubular lumen at the end of fourteenth week.
Within the increase of age and towards senility, the
seminiferous tubules showed progressive degeneration,
reduction in the spermatogenic activity and the
disappearance of the spermatozoa from tubular lumen.
The interstitial tissue was formed by differentiation
of testicular mesenchyme inbetween the testicular cords at
the time of gonadal differentiation.
As development proceeded till the end of fetal life,
an enormous number of interstitial cells was appeared to
occupy nearly the interspaces between the cords and became
numerous also adjacent to the developing tunica albuginea
and at the boundary of the mediastinum testis.
After birth, the interstitial endocrine cells showed
PAS positive cytoplasmic granules, acidophilic finely
granular cytoplasm and cytoplasmic vacuoles. Such structural
changes indicated secretory activity.
With the advancement of age, the mature Leydig cells
had increased in number reaching the phase of puberty.
With the progress of age, a reduction in the number of
the interstitial endocrine cells was noticed. At the senile.