LIGHT AND ELECTRON MICROSCOPICAL STUDIES ON THE GLAND ASSOCIATED WITH THE THIRD-EYELID IN WATER BUFFALO

Document Type : Research article

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Abstract

The water buffalo was characterized by a well-developed gland associated with the third-eyelid in the medial canthus of the eye. It was formed of glandular lobules of tubuloalveolar secretory endpieces. The endpieces were lined by columnar or pyramidal cells. They were divided into light and dark secretory cells with haematoxylin and eosin stain. With application of alcian blue (PH 2,5) - PAS technique, two types of cells were demonstrated. The first type displayed secretory substance of neutral mucin reacting positively with PAS technique. The second type was filled with secretory material formed of a mixture of neutral and acidic mucins, and stained positively with both alcian blue and PAS. The fine structure of type I -cells showed that, the apical accumulated secretory granules were filled with electron dense homogenous material, while in cells of type II, granules containing a mixture of electron dense homogenous patches and fine granular material were observed. In addition, both secretory cells revealed frequently lipid inclusions in close contact with lysosomal material. Ultrastructural sexual dimorphism between male and female glands had been observed. Clusters of cylindrical tubules were usually seen only in male secretory cells. The present findings suggest that the gland associated with the third-eyelid in water buffalo produces seromucous substance by merocrine mode of secretion. Well developed myoepithelial cells formed of cell-body and cytoplasmic processes occupying a position between the basal lamina and basal borders of secretory cells. Naked nerve terminals were located in the intercellular spaces and formed frequently synaptic contacts with both secretory and myoepithelial cells of glandular endpieces. No remarkable morphological differences between the contents of nerve terminals in either regions of neuroglandular or neuromuscular synapses could be detected. Our observations may indicate that the secretory and myoepithelial cells were innervated by one type of nerve terminals. 

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