The palpebral conjunctiva is moderately thick covering the posterior surface of the eyelids and is red in color. The bulbar conjunctiva is thin sensitive very mobile portion which slides back and forth over the eyeball along with its vessels. Within the bulbar conjunctiva are goblet cells and lacrimal glands which secrete mucin that contributes to the tear film, that protects and nourishes the cornea.
(Blue Histology: the eye)
There are slight histological distinctions in the conjunctiva portions. The conjunctiva covering the lid margin and bulbar conjunctiva is a modified nonkeratinized, stratified squamous epithelium. The tarsal and fornix conjunctiva is covered by stratified squamous and cuboidal to columnar epithelium of diverse thickness which preserve some squamoidal characteristics, such as having numerous desmosomes and a microvillus surface. Goblet cells are profuse in the tarsus, fornix, and specialized areas as the plica semilunaris, while they are scant nearby the lid boundary and the cornea's limbus.
A histological sagittal section of both eyelids and the eye are shown here: (1) cornea (2) lens (3) fornix part of the conjunctiva. (4) marginal conjunctiva (5) palpebral portion of the lacrimal gland (6) tarsal conjunctiva. The constitution of Goblet cells within the epithelium at each of these regions is fluctuant. (Anatomy of the Eye: Conjunctiva 2005)