| dc.description.abstract | This study covers the development of the
male bovine gonad from 5 to 66 mm crown-rump
length. The first part of the work deals with the
primordial germ cells which are observed not only
in the mesernhyme of the dorsal mesentery h t also
in the region of the future gonad.
The differentiation of the gonad is
initiated by the thickening of the peritoneal
epithelium on either sidA of the radix esenterii.
At the same time the mesechvme wh.lch is Lmmed.iateLy
below the germinal epithelium proliferates.
Cellular infiltrations from the germinal epithelium
into the under-Ly t n« meser chvme are
observed. The cellular mi.x ture frorn t.he two
tissues forms t+e epithelial-like gonad stroma
f'rom which the different tissues are differentiated.
A gonad that is differentiating into a
testis develops a thin zone of cells jmmedirtely
below the germinal epithelium. These cells
represents fibroblasts and have their elongated
nuclei oriented parallel; to the germinal
epithelium, wnicn becomes greatly reduced to a simple cuboidal or low columnar epithelium. many
primodial germ cells are found between the
epithelial-like mass of the gonad stroma. Only a
small number of these ceLls are between tne ceLls
of tne differentiating tunica albuginea or between
the cells of the germinal epithelium.
The sex cords appear in the gonad stroma
as a network of thin cords of cells. These cords
increase gradually in length and width. Their
portions at or near the tunica albuginea are
always wider than the portions adjoining the rete
testis. Originally, the sex cords are a complex
network. AS growth progresses this complexity is
jgreatly reduced. Most of ~he sex cords become
simple and relatively straight cords. The original
arrangement of the network can still be seen in
older embryos in form of the narrow bridges that
appear to join neighbouring sex cords, and as
branches. In the bovine the sex cords have a
radial orientation with respect to the germinal
epithelium but some of the sex cords are
parallel to it.
The rete testis differentiates both from
the gonad stroma and from the mesonephrogenic
tissue. These two components form a continuous
network of thin cords of epithelial-like cells.
These cords gradually acquire lumina and become
continuous with the tubuli recti on one side and
the ductuti efferentes on the other.
The interstitial tissue of Leydig
differentiates from some of the gonad tissue which
occupies the spaces between the sex cords. The
cells of Leydig are large and strongly
eosinophilic cells with much cytoplasm. They are
in very close association with each other. They
,
first appear between 26 .~ 27 mm CRL in the bovine
male gonad.
The connective tissues of the testis
differentiates from the remaining tissue which is
not incorporated either in the formation of the
sex cords or in the interstitial cells of Leydig.
A group of cells are observed to move from the
area adjoining the renal capsule into the gonad
itself. These cells also contribute towards the
formation of the connective tissue of the testis.
In very young embryos the interstitial
tissue is sparse and the sex cords are sometimes
separated from each other by only their lamina
propria. As growth continues the sex cords are
separated from each other by extensive interstitial
tissue which is always more extensive along the
periphery of the gonad than further inwards towards
the rete testis.
simple cuboidal or low columnar epithelium. Many
premodial germ cells are round between the
epithelial-like mass of the gonad stroma. Only a
small number of these cells are between tne cells
of tne differentiating tunica albuginea or between
the cells of the germinal epithelium.
The sex cords appear in the gonad stroma
as a network of thin cords of cells. These cords
increase gradually in length and width. Their
portions at or near the tunica albuginea are
always wider than the portions adjoining the rete
testis. Originally, the sex cords are a complex
networK. AS growth progresses this complexity is
greatly reduced. Most of the sex cords become
simple and relatively straight cords. The original
arrangement of the network can still be seen in
older embryos in form of the narrow bridges that
appear to join neighbouring sex cords, and as
branches. In the bovine the sex cords have a
radial orientation with res?ect to the germinal
epitl)elium but some of the sex cords are
Rarallel",to it ..
The rete testis differentiates both from
the gonad stroma and from the mesonephrogenic
tissue. These two components form a continuous
network of thin cords of epithelial-like cells.
These cords gradually acquire lumina and become
continuous with the tubuli recti on one side and
the ductuti efferentes on the other.
The interstitial tissue of Leydig
diferentiates from some of the gonad tissue which
occupies the spaces between the sex cords. The
cells of Leydig are large and strongly
eosinophilic cells with much cytoplasm. They are
in very close association with each other. They first appear between 26 ~ 27mm CRL in the bovine -male gonad.
The connective tissues of the testis
differentiates from the remaining tissue which is
not incorporated either in the formation of the
sex cords or in the interstitial cells of Leydig.
A group of cells are observed to move from the
area adjoining the renal capsule into the gonad
itself. These cells also contribute towards the
formation of the connective tissue of the testis.
In very young embryos the interstitial
tissue is sparse and the sex cords are sometimes
separated from each other by only their lamina
propria. As growth continues the sex cords are
separated from each other by extensive interstitial
tissue which is always more extensive along the
periphery of the gonad than further inwards towards
the rete testis. | en |
