HISTOMORPHOLOGY OF THE THYROID GLAND IN THE DOMESTIC FOWL (Gallus domesticus)

Abstract

The histomorphological study of the thyroid gland was carried out using 156 birds in both sexes of layer chicks, growers and layers as well as in broilers of different age groups. The thyroid capsule was made up of collagen,reticular and a few elastic fibres. The reticular fibres were more in younger age groups than in older and were replaced by collagen fibres with aging. The thyroid follicles varied in size and shape both in layer and broiler chicken. The diameter of the follicles showed tendency to increase in size and became irregular in outline with advancing age. The follicular epithelium consisted of two types of cells namely the follicular cells and parafollicular cells. The active follicles were small and spherical in shape which were lined by cells varying from cuboidal to low columnar. The inactive follicles were large, swollen and lined by simple squamous cells. In the follicles lined with cuboidal or low columnar epithelium, the colloid was basophilic whereas in the follicles lined with simple squamous epithelium, it was acidophilic. The parafollicular cells showed argyrophilia in Masson Hamperl's silver stain and metachromasia in masked metachtromasia stain. In aged birds they had eosinophilic cytoplasm