The topographical anatomy and blood supply of the carotid body region of the domestic fowl.

The topographical anatomy of the carotid body region was investigated on both sides in 30 adult domestic fowls (Gallus gallus domesticus). On each side of the body the two parathyroid glands always adhered to each other, the caudal gland being the smaller. The right cranial parathyroid usually touched the thyroid gland, but on the left side the two glands were nearly always separate. The ultimobranchial gland was usually attached to the parathyroid glands on the left side, but was always well separated on the right side. The carotid body, the identity of which was checked by light and electron microscopy, was ovoid in shape, whitish in colour, and about 0.8 x 0.6 x 0.5 mm in size. It was almost always in direct contact with the medial surface of one or both parathyroid glands have commonly been portrayed astopographically separate from each other. The oesophagotracheobronchial artery, the artery to the carotid body, and the caudal thyroid artery arose close together, though in variable positions, from the lateral aspect of the common carotid artery. The artery to the carotid body was always the middle of the three. The venous drainage of the carotid body was associated with the veins of the parathyroid and ultimobranchial glands. The carotid body was innervated by a filament from the distal vagal ganglion. The topographical observations on the carotid body region have been compared with those of other authors. The cranial and caudal parathyroid glands have commonly been portrayed as topographically separate from each other. The carotid body has seldom been depicted in direct contact with the parathyroid glands. The size of the carotid body has invariably been shown far too large. These discrepancies are discussed and are attributed largely to the reliance by other authors on serial reconstruction rather than microdissection.