Hassals corpuscles are spherical or oval bodies present in the thymus. They are phagocytic in function. Adrenal medulla consists of rounded groups of relatively large and granular cells. These cells are called chromaffin cells or phaeochromocytes. Parathyroid glands are formed of two types of cells i.e., small chief cells or principle cells and large oxyphill cells or eosinophil cells. The microscopic structure of thyroid gland shows thyroid follicles composed of. Cubical epithelium and filled with a homogeneous material called colloid.