Thyroid

The thyroid gland consists of two populations of cells of different origin, histological arrangement, and function. The follicular cells secrete thyroxine and triiodothyronine. These hormones regulate development and metabolic rate. The parafollicular cells of the thyroid are of neural crest origin and secrete calcitonin. This hormone is one of the factors regulating calcium and phosphorous balance in the body.

#78 Thyroid, H&E

The thyroid cells are arranged in follicles with hormone-producing cells surrounding a cavity, which is filled with a colloid. The follicles are of various sizes. Observe the relationship of blood vessels to the follicles. The height of the lining follicular epithelial cells reflects the functional state of the follicle. Columnar epithelium is more active than squamous epithelium. Parafollicular cells are found interspersed within the follicular epithelium and in clusters between follicles.