Where is the second point of attachment for the zonular fibers?

The second point of attachment for the zonular fibers is indeed the ciliary processes. Zonular fibers, also known as zonules of Zinn, are fibrous strands that connect the ciliary body to the lens. They play a crucial role in holding the lens in place and facilitating its focusing ability by adjusting its shape through tension.

The ciliary processes are part of the ciliary body, which produces aqueous humor and contains muscles that control the shape of the lens for accommodation. The zonular fibers are anchored to the ciliary processes, creating a connection that allows the ciliary muscle's contraction or relaxation to affect the tension on the lens. When the ciliary muscle contracts, the zonular fibers become less taut, allowing the lens to become more rounded for near vision. Conversely, when the muscle relaxes, the zonular fibers pull on the lens to flatten it for distance vision.

Other structures mentioned do not serve as additional points of attachment for the zonular fibers. The lens equator is the circular midpoint of the lens itself, where the fibers do not attach directly. The iris base refers to the peripheral part of the iris, which does not have any functional connection to the zonules, and the corneal limbus is the border between