Anatomy and histomorphology of thyroid, parathyroid and ultimobranchial glands in Guinea fowl (Numida meleagris)

The thyroid, parathyroid, and ultimobranchial glands are of great importance to birds due to the secretion of various hormones including T3, T4, PTH, and calcitonin, as well as species differences. Since no study was conducted on some birds of the pheasant family such as Guinea fowl, the anatomy, histomorphology, and histochemistry of these glands in Guinea fowl were studied. For this purpose, six adult Guinea fowls (three males and three females) were selected. The anatomical results showed that in Guinea fowl, the thyroid gland was symmetrical in the chest near the cephalic artery, common carotid artery, and the artery under the collarbone. The mean length and width of the thyroid gland in male Guinea fowl was greater than that of the female. In addition, it had a pair of parathyroid glands, so that the right parathyroid gland was adjacent to the right thyroid gland and between the common carotid arteries and jugular vein while the left parathyroid gland was adjacent to the left thyroid gland. Ultimobranchial gland was also a pair with an irregular shape and pinkish color. The left ultimobranchial gland, contrary to the right ultimobranchial gland, was adjacent to the posterior parathyroid gland. Histological and histochemical results were similar to other birds except that in the thyroid gland, the colloid substance in the follicle was not seen as a homogeneous material, but it was seen as isolated fibers both in dark and light colors in the follicle. The dark colloid was seen in the active follicle and the light colloid was seen in the low active follicles. The active follicle wall had a simple cuboidal epithelium and low active follicles had a simple squamous epithelium. Large and active follicles were located around the gland and inactive or low active follicles were in the center of the gland. Under the capsule of the thyroid gland, there were many sections of the blood vessels showing its high blood circulation. The parathyroid gland had a dense connective tissue capsule and composed of chief cells located as cord and cluster in dark and bright colors located in the parenchyma of the sinusoid gland. There was no significant difference between the gland in both males and females. The average length and width of the parathyroid gland in female Guinea fowl were greater than that of the male. Ultimobranchial gland had no capsule. Its main cells were parafollicular or C_cells. Collagen fibers were in the form of a thin capsule around it. In terms of morphology, there was no significant difference between these glands in both males and females. The mean length and width of the ultimobranchial gland are equal in the male and female Guinea fowl.