Topography, irrigation, and histology of the thyroid gland of New Zealand rabbits (Oryctolagus cuniculus Linnaeus, 1758)

Abstract

The objective of this study was to describe the topography, arterial irrigation, and microscopy of thyroid glands of thirty male specimens of New Zealand rabbits (Oryctolagus cuniculus). The aorta-thoracic system was analyzed by aorta thoracic cannulation and fixed in a 10% aqueous formaldehyde solution. Right and left lobes, and the isthmus of the thyroid gland were collected from only three rabbits for microscopic analyses. The procedure followed usual histological routine and histological sections were stained with Hematoxylin/Eosin. The thyroid gland consists of two flat, elongated lobes located ventrolateral to the trachea. Topographically, there is a close relationship between this gland and lateral surfaces of the first five tracheal rings, just below the cricoid cartilage and between the right and left common carotid arteries. The arterial supply to the thyroid gland in both antimers is performed by the thyroid artery, a branch of the common carotid artery. Following its origin at the level of the first tracheal ring, the thyroid artery continues in a caudocranial path. It reaches the cranial part of the thyroid gland and is divided into several branches that are distributed in this organ. The histological sections reveal that the cellular aspect of the isthmus region maintains the same organization and characteristics observed in the thyroid lobes. The thyroid gland in Oryctolagus cuniculus is small, consisting of two bilateral lobes united by an isthmus that presents glandular tissue.

Morphometry, Topography and Arterial Supply of the Thyroid Gland in Brazilian Shorthair Cats

“…The thyroid gland in Brazilian shorthair cat was located ventrolateral to the trachea, which is similar to that observed in dogs [15], jaguarundi cat [6], New Zealand rabbits [4], rats [30], rabbit [33], and domestic ungulates [14], except for pigs who have a thick and compacted glandular tissue on the ventral surface of the trachea [14].…”

“…In 30 New Zealand rabbits, all the animals had an isthmus which established a connection between the cranial and caudal poles of the thyroid gland [4,28]. The absence of the isthmus connecting the thyroid lobes, as observed in a part of the Brazilian shorthair cats, was also reported in diprotodont marsupials [35], house musk shrew [34], and polyprotodont marsupials [31].…”

“…The thyroid artery was a direct branch of the common carotid artery in New Zealand rabbits, too [4,28]. However, both cranial and caudal thyroid arteries irrigated the thyroid glands of some other species, as described in dogs [12,26], jaguarondi [6], and ruminants [15,27].…”

Morphometry, topography and arterial supply of the thyroid gland in rhesus monkeys (Macaca mulatta Zimmermann, 1780)

“…The thyroid gland in rhesus monkeys was located ventrolateral to the trachea, similar to many other domestic and wild mammals (Akudu et al, 2018;Borges et al, 2019;Carvalho et al, 2003;König and Liebich, 2016;Policeni et al, 2012;Rodrigues et al, 2016;Silva et al, 2019;Stocco et al, 2021;Yamasaki, 1990Yamasaki, , 1996Yamasaki, , 2016. However, koalas arranged it laterally to the trachea at the clavicle level (Yamasaki, 1993).…”

“…In Cavia cobaya (Yamasaki, 1994), the thyroid lobes, located laterally to the trachea, showed a uniform morphology, with an isthmus occurring in only a few males and females out of the 60 specimens studied. In New Zealand rabbits, the isthmus was present in all the analyzed animals, connecting the left and right lobes of the thyroid gland (Borges et al, 2019). The topography of the thyroid lobes in New Zealand rabbits varied, with the cranial extremity typically at the level of the cricoid cartilage and the caudal end showing more variability, ranging from the third to the tenth tracheal ring (Silva et al, 2019).…”