LAUSR

| Thyroid gland plays an important role where they produce thyroid and calcitonin hormones. The current investigation was performed on 20 healthy and freshly slaughtered adult male goats. The samples were collected then immediately fixed and processed for the histological and electron microscopical examination of thyroid gland in summer and winter seasons. Thyroid gland was surrounded by a connective capsule with fibrous septa dividing the parenchyma into lobules. Each lobule comprises of several thyroid follicles, also myoepithelial cells were surrounded these thyroid follicles. Semithin sections in the summer season showed that the parenchyma was formed from numerous numbers of inactive follicles, as opposed to the winter season where it had active thyroid follicles. Ultrastructural studies showed that in the summer season the thyroid follicles were lined with flattened to low cuboidal follicular cells, which had little cellular organelles. However, these follicles were lined with high columnar cells that engorged with the colloid droplets and other cell organelles in the winter season. Parafollicular cells were also found beneath the follicular cells that appeared elongated in shape with numerous darkly stained secretory granules.