Which of the following correctly lists the five layers of the cornea from outermost to innermost?

• A. Endothelium, Descemet's membrane, Stroma, Bowman's membrane, Epithelium
• B. Epithelium, Bowman's membrane, Endothelium, Stroma, Descemet's membrane
• C. Epithelium, Bowman's membrane, Stroma, Descemet's membrane, Endothelium
• D. Epithelium, Stroma, Bowman's membrane, Descemet's membrane, Endothelium

Answer: (C)

From front to back, the cornea has five layers in this order: epithelium, Bowman's membrane, stroma, Descemet's membrane, and endothelium. The epithelium is the outer protective surface and heals readily. Bowman's membrane lies just beneath the epithelium as a tough, acellular layer. The stroma is the thick, collagen-rich middle layer that gives the cornea its strength and transparency. Descemet's membrane is the basement membrane for the endothelium, becoming thicker with age. The endothelium is the innermost single layer of cells that helps keep the cornea clear by regulating fluid. Sequences that place the endothelium before the stroma or misplace Descemet's membrane do not reflect the true anterior-to-posterior arrangement.