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Ocular Surface Epithelium: Applied Anatomy

  • Harminder Singh DuaEmail author
  • Dalia G. Said
Chapter
Part of the Essentials in Ophthalmology book series (ESSENTIALS)

Abstract

Anatomically, the ocular surface (OS) covers the area from the lid margins across the palpebral, fornicial and bulbar conjunctiva, the limbal and corneal epithelium. Functionally, the tear film, the glands that produce it, the lacrimal drainage apparatus and the lid blink reflexes all constitute the ocular surface. The OS is an integral part of the mucosal immune system.

The conjunctival epithelium is multilayered near the lid margins but about 2–3 cells thick elsewhere. Goblet cells differentially populate the conjunctival epithelium and produce mucin, which forms the innermost layer of the tear film, providing the hydrophobic epithelium with a hydrophilic cover. Intraepithelial lymphocytes, substantia propria resident white cells and basement membrane fenestrations contribute to its immune function.

The corneal epithelium is a very highly organized structure made of five layers of cells from the superficial flat cells, the middle wing cells and the basal columnar cells that rest on a very regular non-fenestrated basement membrane that provides anchorage to the epithelium with the underlying Bowman’s layer through hemidesmosomes and anchoring filaments. This attachment is stronger at the periphery. The basal cells are capable of rapid mitosis in response to injury and represent ‘transient amplifying cells’. The wing cells are postmitotic.

The limbal epithelium is of variable thickness corresponding to the palisades of Vogt and the inter-palisade rete ridges. The palisades are repositories of stem cells that are particularly abundant in the limbal epithelial crypts, which represent the stem cell niche and extend from the peripheral end of some inter-palisade rete ridges. Corneal epithelial maintenance and replenishment is provided by the stem cells and the basal cells. In the normal physiological state, the basal cells can sustain the central epithelial cell mass but depend on the stem cells for their renewal. In response to injury and insult, the contribution of stem cells is crucial for epithelial wound healing.

The corneal epithelium is endowed with a rich network of sensory nerves from the ophthalmic division of the trigeminal nerve. They serve both trophic and sensory functions, making the cornea the most sensitive structure in the human body. Several pathological conditions such as neurotrophic keratopathy, limbal stem cell deficiency and recurrent corneal erosion syndrome are associated with loss of anatomical structures.

Keywords

Ocular surface epithelium Palisades of Vogt Limbal epithelial crypts Goblet cells 

Notes

Declaration of Interest

None of the authors have any conflict of interest related to the subject matter and content of the chapter. HS Dua is the consultant for Dompe, Santen, Thea and Shire. He has shares in NuVision BioTherapeutics and GlaxoSmithKline. No human or animal studies were carried out by the authors for this chapter.

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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Academic Section of Ophthalmology, Division of Clinical NeuroscienceUniversity of NottinghamNottinghamUK
  2. 2.Department of Ophthalmology, Queens Medical CentreUniversity Hospitals NHS TrustNottinghamUK
  3. 3.Research Institute of Ophthalmology (RIO)CairoEgypt

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