The topographical anatomy and arterial supply of the thyroid and parathyroid glands in the budgerigar [Melopsittacus undulatus]

This investigation was conducted on 30 adult, male and female budgerigars. The thyroid and parathyroid glands adhere to each other on both sides of the body and are surrounded by a common connective tissue capsule. The glandular “cluster” on the right side was cranial and dorsal in relation to that on the left. The thyroid glands were most often supplied with blood by the following glandular arteries: the caudal thyroid (1–4), the cranial thyroid (1–3) and the middle thyroid (1 or 2). The caudal thyroid generally branched from the oesophagotracheobronchial artery. On the right side the cranial and middle thyroid arteries most commonly originated from the ascending oesophageal artery, whereas on the left side they separated from the common trunk of the comes nervi vagi and the ascending oesophageal artery. On each side of the body a single gland was supplied with blood by between 1 and 6 arteries (in most cases by 2–3). On average, the number of thyroid arteries on the right side was statistically significantly higher than the number on the left. The parathyroid artery (1–2) most commonly originated from the caudal thyroid artery, generally separating from this artery under the fibrosus capsule of the glandular “cluster”.