Light and Scanning Electron Microscopy Study on the Structure of Donkey (Equus asinus) Accessory Adrenal Nodules

This study examines the detailed histological architecture of accessory adrenal nodules in 10 male donkeys, employing light microscopy and scanning electron microscopy. The accessory adrenal nodule is situated adjacent to the adrenal gland pole, enclosed in a strong connective tissue capsule that merges with the adrenal gland capsule on one side. The nodule is highly vascularised, and the parenchyma is made up of tissue that looks like adrenal cortical tissue. There is no medullary tissue present. There are four layers in the stroma: the zona glomerulosa, the zona intermedia, the zona fasciculata and the zona reticularis. These layers look like the structure of the adrenal gland. The zona glomerulosa is mostly made up of columnar cells and is close to the capsule. The zona fasciculata, which is the broadest zone, has rows of polyhedral cells that are divided by blood sinuses. The zona reticularis is the innermost zone, and it makes little polyhedral cells. These results provide a significant perspective and enhance our comprehension of the structure of the donkey's accessory adrenal nodule.