Anatomical and Histological Studies on the Lacrimal Apparatus of the Dromedaries with Special Reference to its Clinical Importance

Camels have unique macroscopic and microscopic features of the lacrimal apparatus. This study aimed to describe in detail the anatomy and histology of the lacrimal apparatus in dromedaries in relation to its clinical importance. A total of seven camel heads were used for anatomical studies, and three pairs of lacrimal glands and nasolacrimal ducts were harvested from three heads for histological studies. Macroscopically, the lacrimal gland was formed of an orbital and palpebral part. The nasolacrimal duct showed a peculiar S-shaped course, and it was notably dilated at the end of its membranous portion. Microscopically, this dilated part of the duct showed a microscopic diverticulum of a few millimeters in length. This diverticulum was lined by stratified squamous epithelium while the duct lining was pseudostratified. To the best of the author's knowledge, this is the first report for such diverticulum in camels. In addition, intra-epithelial mucous glands were also recorded within the mucosa of the palpebral conjunctiva, and Meibomian glands were found within the tarsus of the upper and lower eyelids. Clinically, it is not recommended to do dacryocystography in camels because of the possibility of rupture of the microscopic diverticulum of the nasolacrimal duct. In conclusion, camels had three sets of glands necessary for precorneal tear film formation, and the nasolacrimal duct had unique structures.