Location: in the neck antrolateral to the larynx and upper trachea.
Function: production of hormones, which are essential to normal metabolism and homeostasis.
Composition: a thin connective tissue capsule surrounds the gland. It sends trabeculae with fenestrated capillaries into the parenchyma. The follicle is the structural unit of gland. It is a spheroidal cyst-like compartment with a wall formed by a simple squamous or cuboidal epithelium.
Origin: downward growth of endoderm of the floor of the pharyngeal portion of the foregut.
Function: Thyroxin (tetraiodothyronine, T4) and triiodothyronine (T3) regulate cell and tissue metabolism.
Origin: neural crest cells that migrate into the developing gland.
Function: Calcitonin (thyrocalcitonin) lowers blood calcium levels.