The Conjunctiva

Parts of the Conjunctiva

1. Palpebral conjunctiva
   • This lines the lids and can be divided into marginal, tarsal and orbital conjunctiva.
2. Bulbar conjunctiva
   • Covers the anterior sclera and is separated from it by episclera tissue and tenon’s capsule.
   • It is loose, thin and transparent and can move easily.
   • Around the limbus, it is called the limbal conjunctiva.
   • At the limbus, the epithelium of the conjunctiva becomes continuous with that of the cornea.
3. Fornical/fornix conjunctiva
   • This is a continuous cul-de-sac connecting palpebral and bulbar sections.

Layers

The conjunctiva consists of 3 layers – epithelium, adenoid layer and fibrous layer:

1. Epithelium – has 2-5 layers of stratified squamous cell epithelium. The superficial epithelial cells contain round or oval mucus-secreting goblet cells. This mucus forms the mucin layer of the tear film.
   • Other mucus secreting glands include glands of Manz, and crypts of henle.
2. Adenoid layer – also called the lymphoid layer, contains lymphoid tissue.
3. Fibrous layer – consists of a meshwork of collagen and elastic fibres.

The accessory lacrimal glands (glands of Krause and Wolfring), which resemble the lacrimal gland in structure and function, are located in the stroma.

NB: The adenoid (superficial) layer and fibrous (deep) layer form what we call the conjunctival stroma.

Functions

• Motility of the eyeball because of its looseness.
• Protective function against pathogens.
• Protection of the cornea by lubricating it during the blinking reflex.
• When the eyelids are closed, it covers the cornea and supplies oxygen and other metabolic needs.

Plica semilunaris

• Crescent-shaped fold of conjunctiva located at the medial canthus.

Caruncle

• Small ovoid, pinkish mass at the inner canthus, just medial to plica seminunaris.
• In reality, it is a piece of modified skin and so is covered with stratified squamous epithelium and contains sweat glands and follicles.

Blood supply

• Arterial supply is by posterior conjunctival vessels which come from branches of ciliary arteries (anterior circle of iris).
• Venous return is through venous plexus of the eyelids and some around the cornea into anterior ciliary veins.
• Lymphatic drainage:
  • Lateral side drains into pre auricular lymph nodes
  • Medial side into sub mandibular lymph nodes

Nerve supply

• Motor nerve – the circumcorneal zone is supplied by long ciliary nerves which supply cornea.
  • Rest of the conjunctiva is supplied by the branches of lacrimal, infratrochlear nerves (which are also branches of maxillary nerve), supratrochlear and supraorbital and frontal nerves which are branches of the ophthalmic nerve.
• Sensory nerve is the trigeminal nerve.