Histology, Histochemistry and Scanning Electron Microscopy of Conjunctiva and Conjunctiva Associated Lymphoid Tissue in Domestic Pigs (Sus scrofa domesticus)

Abstract

The present study was conducted on palpebral and bulbar conjunctiva of six healthy adult pigs of either sex. Superior and inferior palpebral conjunctiva was lined by stratified squamous non-keratinized epithelium at the lid margin which was gradually changed from stratified cuboidal to the columnar epithelium with numerous goblet cells. Diffusely arranged lymphoid cells were profoundly observed as intraepithelial lymphoid tissue as well as in the form of a subepithelial lymphoid layer in the lamina propria. Aggregated as well as solitary lymphoid follicles were also observed associated with epithelium. The lymphoid follicles were usually comparatively more in the lower eyelid. The population of goblet cells was very less in bulbar conjunctiva compared to palpebral conjunctiva and not observed at limbus. A layer of elastic fibres was observed just beneath the epithelium and elastic fibres were present abundantly in the lamina propria of bulbar conjunctiva. Lymphoid follicles in the bulbar conjunctiva were not observed however few scattered lymphoid cells were seen. Scanning electron microscopic view of the superior and inferior palpebral conjunctiva towards the lid margin showed different stages of the superficial cells of the stratified squamous epithelium that having microplicae of various sizes and shapes. Few small holes were observed which might be for the opening of the goblet and their density was increased towards the fornix.