Question

19. List the layers of the Cornea. Describe the structure sf each

Answer 1

Cornea: It is a transparent layer of eye that refracts light. Human cornea has five layers. They are:

• Epithelium: It is made of non-keratinized stratified squamous epithelium. The cells form about 6 layers. They are constantly shed off and are replaced by new cells.

• Bowman’s layer: Tough fibrous layer composed of type-I collagen fibers, laminin, nidogen, and perlecan. It provides the subepithelial basement membrane and protects the stroma of cornea. There are no cells in this layer.

• Stroma: This layer too composed of collagen fibers, but with interspersed keratocytes that help in repair and maintenance of the layer. The layer is thick and transparent, and is composed of several overlapping layers of collagen fibers.

• Descemet’s membrane: It is thinner than stroma, and is a modified basement membrane. It is acellular, mainly composed of type IV collagen fibers which are relatively less rigid.

• Endothelium: Composed of squamous cells, it forms a monolayer of cells rich in mitochondria. The layer is involved in regulation of solute and fluid transport between the aqueous humor and stromal regions. Corneal endothelial cells cannot be replaced once lost, but the existing cells stretch to compensate for dead cells.