Ans. is 'c' i.e., Posterior surface Anatomy of crystalline lens There are three structural elements that make up lens - 1. Lens capsule A transparent membrane surrounding the lens like a pocket. It is thicker over the anterior surface than the posterior surface. It is thickest at pre- equator region and thinnest at the posterior pole. When an aificial lens replaces the natural lens in cataract surgery (IOL implantation), it is placed in this same capsule. 2. Lens epithelium It is a single layer on the anterior (front) surface of the lens. There is no epithelium on posterior surface. The epithelial cells distribute fluid, ion and glucose through the entire lens. They also create new fibers throughout a person's life. 3. Lens fibres These are long protein fibers that arc closely packed and parallel. They make up most of the lens volume and are laid horizontally, front to back, and concentrically like layers of an onion.As the lens fibres are formed throughout the life, these are arranged compactly as nucleus and coex of the lens. a) Nucleus : - It is the central pa containing the oldest fibres. it consists of different zones :- Embryonic nucleus :- Formed at 1-3 months of gestation, therefore consists the oldest primary fibres. Fetal nucleus : - Lies around the embryonic nucleus and is formed from 3 months of gestation till bih. Infantile nucleus :- Corresponding the lens from bih to pubey and surrounds the fetal nucleus. Adults :- Corresponds to the lens fibres formed after pubey to rest of the life. Coex :- It is the peripheral pa containg the youngest fibres. The ciliary zonules (Zonules of zinn or suspensory ligaments of lens) hold the lens in position and enable the ciliary muscle to act on it. These consist essentially of a series of fibres which run from the ciliary body and fuse into the outer layer of the lens capsule around the equatorial zone.