The lens develops from which embryonic structure?

• A. Optic vesicle
• B. Lens placode
• C. Neural tube
• D. Surface ectoderm

Answer: (B)

The lens forms from a thickening of the surface ectoderm over the developing optic vesicle called the lens placode. This placode arises in response to signals from the underlying optic vesicle, then invaginates to form the lens pit and eventually the lens vesicle, whose cells differentiate into the lens. So the direct embryonic structure that becomes the lens is the lens placode. The optic vesicle helps induce this process, while surface ectoderm is the broader tissue of origin, and neural tube is unrelated to lens development.