Explain about the barrier function of epithelium and endothelium in corneal hydration.
Barrier Function of Epithelium and Endothelium:
Epithelium offers twice the resistance as endothelium. Barrier function of epithelium is maintained by desmosomes, mitotic activity of basal cells and migration of limbal stem cells into basal cell layer. Corneal endothelial barrier is leaky compared to epithelium. The permeability results from low resistance intercellular junctions at apical basement membrane. The tight junctions do not form complete zona occludens around the cells. The endothelial barrier function is calcium dependent.