This low magnification
image of a plastic section of the thyroid gland shows the general organization.
The gland is covered by a thick connective tissue capsule, containing adipose
cells and blood vessels. The parenchyma of the gland is composed of large
numbers of irregularly shaped thyroid follicles
of various sizes. The wall of the follicles are formed by a single layer of
cuboidal to low columnar follicular cells with
circular nuclei. The follicles are filled with eosinophilic thyroid
colloid, the storage-form of thyroid hormone. In the connective tissue
between the follicles are large numbers of anastomosing capillaries
lined by endothelial cells with flattened, darkly
stained nuclei.
