Light micrograph section of an adult parathyroid gland stained with haematoxylin-eosin. The glandular parenchyma is made up of thick cell cords in which two cell types can be distinguished. The chief cells of very small size, with the nuclei very close to each other and the oxyphilic cells, of greater size and with eosinophilic cytoplasm, which often coalesce to form nodules. Among the cords are connective tissue septa that show abundant blood vessels (very striking arterioles and venules) and adipocytes that occupy an important part of the septum.