The ultrastructure of the normal conjunctival epithelium of the guinea pig. III. The bulbar zone, the zone of the fornix and the supranodular zone.

Three adjacent zones of the conjunctival epithelium of the guinea pig are described: the three-layered bulbar zone with cuboidal superficial cells, the three-layered zone of the fornix with cylindrical superficial cells, and the four- to five-layered supranodular zone characterized by close association with a lymphoid nodule. The similarities and differences in the general morphology of the epithelium and in the ultrastructural features of the cells, as compared to those of the perilimbal zone, are pointed out. The functional significance of atypical mitochondria found in certain cells of the bulbar and fornical zones is commented upon. Particular attention is paid to the supranodular zone, containing a large number of intraepithelially located lymphocytes. The possible role of an epithelium associated with subepithelial lymphoid tissue in the immune defense is discussed.