A) pupil
B) iris
C) optic nerve
D) ciliary muscles
Correct Answer: D
Solution :
The mammalian eye has three layers sclera, uvea and retina. The uvea is composed of choroid ciliary body and iris. The ciliary body is a tiny circle of smooth muscle around the interior of the eyeball. The ciliary muscle controls visual accommodation, i.e., due to action of ciliary muscles focal length of the lens can be changed. The iris is a thin continuation of uvea across the front of eyeball. The pupil is not a structure but an opening defined by the free edge of the iris. Optic nerve is not a nerve but a sensory tract, it is a collection of fibres in CNS. Embryologically it develops as an out pocketing of thebrain. However once it is differentiated, it lies outside the brain. Its fibres synapse in the thalamus and midbrain.
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