Abstract
Background:
The adrenal gland of the avian is considered a critical organ in the body because its hormones coordinate and control many pivotal physiological actions.

Aim:
The current research aimed to describe the ultrastructural, macroscopical, and histological characteristics of the adrenal gland in swan geese using electron and light microscopy, as well as perform a gross investigation.

Methods:
Twelve healthy swans were purchased from a bird market in Baghdad. After the swans were euthanized, the adrenal glands were immediately examined morphologically and histologically using standard histological techniques.

Results:
Morphological findings clarified that the adrenals were a yellowish structure, found close to the gonads, and were cranial to medial for each kidney. A significant variation in length and weight was observed between the two glands. High significance difference in female vs. male microscopically, they were covered with a thin capsule containing blood capillaries scattered between their fibers. In addition to several blood sinusoids, two intermingled types of tissue constituted the gland parenchyma: the medullary and cortical tissues. The layer is subdivided into the central zone, peripheral zone, and subcapsular layer. Small islets of chromaffin cells representing medullary tissue were distributed throughout the cortical portion. Ultrastructurally, the cortical cells showed numerous globules, curved cords, and blebs.

Conclusion:
The adrenal structure in swans exhibits that the amount of cortical tissue is higher than that in the medullary gland, indicating the physiological need for cortical tissue secretions since they are migratory birds.

Key words: Cords, Electron microscopy, Swan, Medulla