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Subject: Veterinary Anatomy and Histology × Author: RAJASHAILESHA, N. M. × End date: 2019 × Start date: 2014 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    GROSS, HISTOLOGICAL AND HISTOCHEMICAL STUDIES ON THE EYEBALL AND EXTRAOCULAR MUSCLES OF SLOTH BEAR (Melursus ursinus)
    (KARNATAKA VETERINARY, ANIMAL AND FISHERIES SCIENCES UNIVERSITY, BIDAR, 2018-07) RAJASHAILESHA, N. M.; Dr. R. V. PRASAD
    The present study was conducted on the gross, histological and histochemical studies on the eyeball, extraocular muscles and bony orbit of sloth bear. The bony orbit was oval in shape with incomplete bony rim and formed by six bones. The shape of the eyeball was almost circular and lens was biconvex in shape. The color of the iris was dark brown and pupil was circular. Choroid showed the presence of semicircular tapetum and its base was placed horizontally ventral to the optic papilla. Extraocular muscles were seven in number, muscle dorsal oblique was longest. The corneal epithelium showed the presence of naked nerve endings and iron pigments in their cytoplasm. Histologically, the iris was made up of stroma, iridial muscles and a posterior epithelium and granula iridica was round and found at the tip of the iris. Tapetum was made up of rectangular shaped cells which were oriented in a brick-like manner. Well distinct Bruch’s membrane was observed. The iron pigments were appreciated in pigmented epithelium of retina and it was devoid of melanin pigments in the area adjacent to tapetal layer of the choroid. In the outer nuclear layer, the nuclei of rods were darkly stained and abundant in number, whereas, nuclei of cones were lightly stained and were few in number. In the inner nuclear layer horizontal cells were located adjacent to outer plexiform layer, bipolar cells were oriented radially with centrally located large heterochromatic nucleus, Muller cells were oriented radially, elongated and located in between bipolar cells. Amacrine cells were located in the innermost aspect of the inner nuclear layer, and capillaries were also observed in the inner nuclear, inner plexiform, ganglionic and nerve fiber layer indicating holangiotic pattern of retina. The nerve fibers converge at the optic disc and emerge as optic nerve and optic papilla was goblet shaped. Extraocular muscles were skeletal in nature showing fast and slow twitch based on the granular and homogenous muscle fibers histologically. Presence of intense PAS positive character indicated EOMs are highly metabolically active and participate in aerobic metabolism.