Which structure contains a ring of muscles that surround the lens and control its shape?

Which structure contains a ring of muscles that surround the lens and control its shape?

• A. Iris
• B. Choroid
• C. Ciliary body
• D. Retina

Answer: (C)

The structure that contains a ring of muscles around the lens and controls its shape is the ciliary body. Its ciliary muscle forms a circular band around the lens and adjusts lens curvature by changing the tension on the suspensory ligaments (zonular fibers). When the ciliary muscle contracts, it releases tension on the ligaments, allowing the lens to become more curved for near vision. When it relaxes, the ligaments tighten and the lens becomes flatter for distant vision. The iris also forms a ring around the pupil but it does not surround the lens, the choroid is a vascular layer beneath the retina, and the retina is the light-sensitive layer. Hence, the ciliary body is the correct structure.

The structure that contains a ring of muscles around the lens and controls its shape is the ciliary body. Its ciliary muscle forms a circular band around the lens and adjusts lens curvature by changing the tension on the suspensory ligaments (zonular fibers). When the ciliary muscle contracts, it releases tension on the ligaments, allowing the lens to become more curved for near vision. When it relaxes, the ligaments tighten and the lens becomes flatter for distant vision. The iris also forms a ring around the pupil but it does not surround the lens, the choroid is a vascular layer beneath the retina, and the retina is the light-sensitive layer. Hence, the ciliary body is the correct structure.