Thyroid Gland Anatomy - (embryology, blood supply, venous drainage, innervation, histology)

The thyroid gland is butterfly shaped endocrine organ that sits and wraps around the trachea. It produces three main hormone T3 and T4 important in metabolism and calcitonin in calcium homeostasis. The thyroid has two main loves the right and left. Anteriorly the thyroid glands are joined by the Isthmus. Posteriorly the thyroid gland encircles the tracheal rings but does not connect. From this dorsal view we can see 4 parathyroid glands sitting on the thyroid gland, 2 on each side. Developmentally, the thyroid isthmus can give rise to a structure contiguous called the pyramidal lobe, which extends upward. The pyramidal love is common up to 55% and is a result of the persistent remnant of the thyroglossal duct. The functional unit of the thyroid gland is the follicle. The follicles are made up of a central cavity filled with a sticky fluid called colloid. Surrounded by a wall of epithelial follicle cells, the colloid is the center of thyroid hormone production. Surrounding the follicles are capillaries. Follicular cells produce the classical thyroid hormones, thyroxine and triiodothyronine. The production of these hormones in the colloid rely on iodine.