Absence of Hyaline Cartilage in the Tongue of 'Caspian Miniature Horse'

Summary Histology of the tongue, including apex, root and body, in four adult Caspian miniature horses was examined. Serial sections with 6 μm thickness were stained with haematoxylin–eosin and Masson trichrome and studied under light microscope. The tongue was covered by stratified squamous epithelium. It was thick and keratinized bearing numerous lingual papillae on the dorsum, mostly filiform with a very fine keratinized thread projecting above the surface and bending backward. The fungiform papillae were sparsely scattered among the filiform papillae and covered with keratinized squamous epithelium. Few taste buds were detected on it. The two very large vallate papillae were detected on the dorsum, just rostral to the root, which were covered with stratified squamous epithelium with relatively high amounts of taste buds in the epithelium of the surrounding grooves. The foliate papillae were present near the palatoglossal arch and had a few taste buds. The epithelium covering the ventral surface of the tongue was thin and keratinized. The lingual muscle core consisted of transverse, longitudinal and perpendicular bundles of skeletal muscle fibres. Clusters of minor salivary glands were present between the muscle fibres and lamia propria. Most of the lingual glands were mucous and most of the gustatory ones were serous type. The mid-dorsal special structure of the tongue (dorsal lingual cartilage) contained sparse skeletal muscle fibres and was rich in white adipose tissue. Hyaline cartilage, routinely observed in this structure in the horses, was not detected in Caspian miniature horse.