Histological and Histochemical Study of Thyroid Gland in Bull (Bos Taurus) in Al Muthanna province

The current study aimed to finding of the histological and histochemical characteristics of the thyroid glands in adult males of bull . Fifteen adult male bull to was used in this study. Histological study was used to describe the general structure of thyroid, in addition to microscopic measurements included the thickness of capsule, diameter of different thyroid follicles. According to histological findings, the thyroid glands in each animal had a capsule covering them that was made up of two layers of collagen fibers. Thyroid gland follicles in three different shapes and sizes made up every lobe of the thyroid gland: large, medium, and small follicles . The histological result revealed the Para follicular cells in the bull, also referred to as C-cells. C-cells are large, spherical, and oval in shape, and their cytoplasm was stained lighter than that of follicular cells. Their nuclei were also densely stained. They began as a single cell or in groups of two or three. In the tissue section, it was observed that certain C-cells were supported by a basement membrane, serving as the bases of both follicular and Para follicular cells. In contrast, other cells were arranged haphazardly in the intermolecular tissue, separating the Ccells from the follicular wall. The Para follicular cells, which were observed in tissue sections either singly or in small groups, have an oval or rounded shape, a spherical nucleus, and light stain cytoplasm . Histochemical results showed that the capsule, colloid material, basement membrane and Para follicular cells of thyroid gland showed intense reactions. To PAS stain All parts of thyroid l glands was exhibited positive reaction to Alcian blue_ PAS and Masson Trachoma stain