Topography and arterial supply of the thyroid and the parathyroid glands in selected species of Falconiformes.

Birds of two suborders, Accipitres and Falcones were the subjects of the study. The thyroids were always located asymmetrically. In Accipitridae the larger left gland was usually situated significantly more cranially than the right one. In common kestrel, the size of bilateral thyroids was similar while their mutual relationships were individually variable. The location of the parathyroid glands in common kestrel was relatively constant. Seven topographical patterns of the location of the parathyroid gland were noted in Accipitridae. In birds of both the suborders, the thyroid might be supplied by three (groups of) arteries: the cranial thyroid, the caudal thyroid and the middle thyroid arteries. The aforementioned vessels were derived from the common carotid and the oesophagotracheobronchial artery. In common kestrel, the thyroid vessels might also branch from the ascending oesophageal artery, which passes along the thyroid, while in common buzzard and other Accipitridae - from the common trunk of the comes nervi vagi and the ascending oesophageal artery. The parathyroid glands were supplied by one to three parathyroid arteries. The vessels for the cranial parathyroid gland mostly originated from the caudal thyroid artery, while for the caudal one - from the oesophagotracheobronchial artery. The average number of thyroid and parathyroid arteries in common buzzard was significantly higher than those in common kestrel.