ANATOMICAL STUDIES ON THE THYROID GLAND IN BAKARWALI GOAT (CAPRA HIRCUS)
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Date
2017
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Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu
Abstract
The study was conducted on the thyroid gland of 36 Bakerwali goats divided into three age groups based on age. After conducting gross studies, histological, micrometrical and histochemical, ultrastructural observations were made from sections obtained from right lobe, left lobe and isthmus of the thyroid glands. The gland was bilobed, reddish brown in colour, elongated and elliptical in outline. The right lobe of the gland extended from posterior extremity of larynx to 5th tracheal ring while as left lobe extended from posterior extremity of larynx to 7th tracheal ring. The two lobes were connected by isthmus around the ventral aspect of trachea and position vary between 5th and 6th tracheal ring irrespective of age groups. The mean biometrical values increased between succeeding age groups. The isthmus was glandular band connected the lateral (right and left) lobes of the thyroid gland. The thyroid gland was covered with distinct capsule, comprised of three layers: outer layer, middle layer and inner layer. The reticular fibers formed wire mesh like structure around the follicles. The small and medium size follicles were mostly seen in the peripheral zones whereas larger and abnormally large follicles were seen in the deeper zone of the gland. In prepubertal group only small and medium sized follicles were observed. In pubertal group, small, medium and large size follicles were seen while in senile group abnormally large size follicles were also reported besides the medium and large size follicles. The thyroid follicles were lined by epithelium which varied from squamous epithelium to high cuboidal or columnar with flattened to rounded well defined nuclei, respectively. The inactive follicles were usually large and active follicles were smaller in size irrespective of age groups. The parafollicular cells were characterized by light stained and basophilic cytoplasm. Various micrometrical parameters showed significant (P≤ 0.05) difference between prepubertal and senile age groups. Ultramicroscopic studies showed the cuboidal follicular cells with nucleus having heterochromatin concentrated marginally on the nuclear membrane as irregular layer in prepubertal group. In pubertal group scattered clumps of chromatin was observed in the nucleus. In senile group, the squamous epithelial cells with flattened nucleus, while cuboidal cells with rounded nuclei was observed. The content of neutral mucopolysaccharides, basic proteins and glycogen in thyroid gland increased with age. The level of T3 and T4 increased from prepubertal to pubertal group and then decreased in senile group.
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