Microscopic Focus on the Thyroid Follicles of the One-Humped Camel (Camelus dromedarius)

The microstructure of the thyroid gland of the one-humped camel (Camelus dromedarius) was described using morphometric, histological, immunohistochemical staining, and ultrastructural standard techniques. The follicular secretory units of the thyroid glands displayed comparable and variable sizes where the large follicles were situated at the peripheral margins; however, the small ones were located in the central region. Semisquamous epithelium (low cuboidal) lined the large thyroid follicles, while high cuboidal (columnar) epithelium lined the small ones. Our electron microscopic findings revealed that the low-sized cuboidal follicular cells lack organelles and are hypoactive. The high cuboidal follicular cells are active cells and rich in cellular organelles such as cisternae of rough endoplasmic reticulum, mitochondria, colloid droplets, scrolled Golgi apparatus, and secretory vesicles. A few degenerate follicular cells appeared on rare occasions. The parafollicular cells appeared with a more prominent and conspicuous nucleus than the follicular cells. The follicular cells were classified as active, inactive, or degenerated using transmission electron microscopy. The follicular and parafollicular cells showed calcitonin-positive immunoreactivity. Overall, the presented results showed particular convergences of the morphostructural aspects of the thyroid gland of C. dromedarius to that of other mammals with some distinctive features to cope with their physiology and harsh niche.