The thyroid gland is located in the neck, in close approximation to the first part of the trachea. Most animals, however, have two separate glands on either side of the trachea.
Thyroid glands are brownish-red in color.
The image to the right shows a canine thyroid gland and one attached parathyroid gland. The microscopic structure of the thyroid is quite distinctive. In standard histologic preparations such as these, colloid stains pink. In addition to thyroid epithelial cells, the thyroid gland houses one other important endocrine cell. Nestled in spaces between thyroid follicles are parafollicular or C cells , which secrete the hormone calcitonin.