Conjunctiva Organ and Cell Culture
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Conjunctiva, the mucous membrane of the eye, covers its surface from the limbus, the junction with the cornea, to the edges of the eyelids where it meets the skin, thus forming a blind sac that permits free movement of the eye. Topologically, the conjunctiva is divided into bulbar (covering the sclera, adherent at the limbus), tarsal (lining the lids), and fornical (from the medial “corner” of the eye). At the limbus, where putative corneal stem cells reside, a barrier whose nature has yet to be determined stops conjunctival epithelium from migrating over the cornea. When this barrier is damaged, the migration of conjunctiva over the cornea is accompanied by invasion of blood vessels and, consequently, loss of sight. There is a change in morphology from the fornix, where cylindrical cells give rise to a columnar stratified conjunctival epithelium, to the limbus and lid margins where flattened cells result in a squamous stratified tissue ( 1 ). In rodents and rabbits, goblet cells appear in clusters. Their apical openings are decorated with actin collars ( 2 ). These are not seen in human tissue, where goblet cells may appear either singly ( see Fig. 1 ) or in clusters. Although these cells are larger than the surrounding squames, they do not necessarily span the entire epithelial thickness.
Fig. 1. Confocal x-z (transversal) scan of normal human conjunctival epithelium. Actin in the cell cytokeleon has been visualized with Phalloidin. The goblet cell can be recognised by its shape and cross-reaction with antibody 45M1 to MUC5AC. The latter is difficult to distinguish on this gray-scale image. The stippling at the apical surface of the superficial epithelial cells are intercellular junctions.
