During lens development, which statement correctly describes the fate of the posterior cells of the lens vesicle?

• A. Anterior lens epithelium differentiates into the corneal endothelium.
• B. The posterior cells of the lens vesicle become the corneal endothelium.
• C. The posterior cells remain undifferentiated to form the lens capsule.
• D. Posterior cells elongate to form primary lens fibers.

Answer: (D)

During lens development, the posterior cells of the lens vesicle actively differentiate by elongating to form the primary lens fibers. These elongated cells extend toward the center of the vesicle, filling it and establishing the embryonic nucleus of the lens. The anterior surface remains as the anterior lens epithelium, which later gives rise to secondary lens fibers at the equator to add to the lens throughout life. The corneal endothelium comes from neural crest–derived cells, not from the lens vesicle, and the capsule is produced by the lens epithelium and differentiating fibers rather than by remaining undifferentiated posterior cells. So the posterior cells becoming primary lens fibers best describes their fate.