Plica semilunaris of conjunctiva
Plica semilunaris conjunctivae
- Related terms: Plica semilunaris
Definition
The plica semilunaris of conjunctiva is a crescent-shaped fold of conjunctiva located at the medial canthus of the eye, lateral to the lacrimal caruncle. It represents a rudimentary vestigial form of the nictitating membrane (third eyelid) found in many lower vertebrates.
Histology
Histologically, plica semilunaris of conjuctiva is lined by nonkeratinized stratified columnar epithelium containing goblet cells. Beneath the epithelium lies a loose vascular connective tissue layer rich in elastic fibers, lymphoid tissue, and immune cells.
Functions
Functionally, the plica semilunaris allows greater mobility of the eyeball by accommodating conjunctival movement during ocular rotation. It also contributes to distribution of the tear film and protection of the ocular surface.
References
Standring, S. (Ed.). (2015). Eye (Chapter 42). In Gray's anatomy: The anatomical basis of clinical practice (41st ed., pp. ). Churchill Livingstone.
Shumway CL, Motlagh M, Wade M. Anatomy, Head and Neck, Eye Conjunctiva. [Updated 2023 Aug 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519502/
