STUDIES ON THE PRENATAL DEVELOPMENT OF TESTIS IN SHEEP (Ovis aries)
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Date
2016-12
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT:
The present study was undertaken to elucidate the developmental changes in
the testis. The study was conducted on 38 embryos and foetuses of sheep collected
from local abattoirs from 37 to 122 days (0.7 to 41 cm CRL) were collected and
divided into three age groups basing on gestation periods. In group I, at 42 days of gestation, testes were located in between the metanephric kidneys medially and mesonephros laterally in the lumbar region and scrotal bud was first observed in the inguinal region. At 59 days of gestation, the testes were located at caudal pole of kidney. At 94 days of age, the descent of testes into the scrotum was completed. At 122 days of gestation, testes were located in the
scrotal sac. At 44 days of gestation, testes were oblong in shape but testes were changed to oval at 46 days of foetal life later became elongated at 60 days of gestation. The genital ridge was first observed between the mesonephoros and primitive gut in 37 day old sheep foetus. At 39 days of gestation, the gonadal anlages protruded into the coelomic cavity as paired oval-shaped structures on either side of the dorsal mesentery of the hindgut medial to the mesonephros. At 44 days of gestation, mesenchymal cells beneath the germinal epithelium
were transformed to tunica albugenia. Sex cords were first appeared at 44 days foetal
testes. The dark small cells were modified to form Sertoli cells and were first
observed at 46 days of gestation. At 69 days, the lumenization was observed in more
number of seminiferous tubules. At 94 days, very few tubules were closely adherent
with the endothelial cells and formed blood testes barrier. At 46 days of foetal life, the
interstitial endocrine cells gradually modified to form isolated Leydig cells.
At 44 days of gestation, the central area of the testis was devoided of sex cords
and tailored as mediastinum testis. In group III, the mediastinum consisted of densily
packed collagen and reticular fibres in between the rete tubules. At 73 days of
gestation, the density of cell clusters in the area of mediastinum testes was increased.
Vacuolation was observed in the central area of cell clusters resulted in the initiation
of the lumen formation in rete testis. Histochemical studies of testes revealed that in group III at 122 days of gestation, intense positive reaction in the capsule, basement membrane of
seminiferous tubules and blood capillaries was identified for mucopolysaccharides.
Intense positive reaction was identified in the capsule, basement membrane of
seminiferous tubules and blood capillaries for glycogen at 122 days. In group II and
III mild reaction for lipids in the capsule was recorded.
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THESES
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