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The corneal limbus is the border between the cornea and the sclera. [2] It is highly vascularized. [2] The corneal limbus' responsibilities include protection, healing, and controlling eye pressure. The limbus contains corneal stem cells that play key roles in corneal healing (renewing the corneal epithelium). [3]
The corneal epithelium (epithelium corneae anterior layer) is made up of epithelial tissue and covers the front of the cornea. It acts as a barrier to protect the cornea, resisting the free flow of fluids from the tears, and prevents bacteria from entering the epithelium and corneal stroma.
Limbal stem cells, also known as corneal epithelial stem cells, are unipotent stem cells located in the basal epithelial layer of the corneal limbus. They form the border between the cornea and the sclera. Characteristics of limbal stem cells include a slow turnover rate, high proliferative potential, clonogenicity, expression of stem cell ...
All squamous cell carcinoma lesions are thought to begin via the repeated, uncontrolled division of cancer stem cells of epithelial lineage or characteristics. Accumulation of these cancer cells causes a microscopic focus of abnormal cells that are, at least initially, locally confined within the specific tissue in which the progenitor cell resided.
The fibrils of each lamella are parallel with one another, but at different angles to those of adjacent lamellae. The lamellae are produced by keratocytes (corneal connective tissue cells), which occupy about 10% of the substantia propria. Apart from the cells, the major non-aqueous constituents of the stroma are collagen fibrils and proteoglycans.
The normal cornea (Fig 1) has from the front to the back the following layers: 1. Epithelium 2. Bowman's membrane 3. Stroma 4. Pre Descemets layer 5. Descemet's membrane 6. Endothelium For the human eye to see, the cornea or the front window of the eye should be clear or transparent.
Surface ectoderm forms the lens, corneal epithelium and eyelid. The extracellular mesenchyme forms the sclera, the corneal endothelium and stroma, blood vessels, muscles, and vitreous. The eye begins to develop as a pair of optic vesicles on each side of the forebrain at the end of the fourth week of pregnancy.
Keratocytes are developmentally derived from the cranial population of neural crest cells, from whence they migrate to settle in the mesenchyme.In some species the migration from neural crest comes in two waves, with the first giving birth to the corneal endothelium and the second invading the epithelium-secreted stromal anlage devoid of cells; in other species both populations come from a ...