Where does the optic nerve begin to become myelinated?

Where does the optic nerve begin to become myelinated?

• A. Lamina cribrosa
• B. Retina
• C. Optic disc
• D. Chiasm

Answer: (A)

Myelination of the optic nerve fibers begins as the retinal ganglion cell axons exit the eye and pass through the lamina cribrosa into the optic nerve. In the retina and at the optic disc, these fibers remain unmyelinated; it is behind the lamina cribrosa that oligodendrocytes wrap the axons with myelin. The lamina cribrosa marks this boundary where myelination starts, continuing posteriorly in the optic nerve. The chiasm is further back in the brain and contains already myelinated fibers, not the starting point.

Myelination of the optic nerve fibers begins as the retinal ganglion cell axons exit the eye and pass through the lamina cribrosa into the optic nerve. In the retina and at the optic disc, these fibers remain unmyelinated; it is behind the lamina cribrosa that oligodendrocytes wrap the axons with myelin. The lamina cribrosa marks this boundary where myelination starts, continuing posteriorly in the optic nerve. The chiasm is further back in the brain and contains already myelinated fibers, not the starting point.