Which of these is not the part of the eye?

Analyze the question: You are asked to pick the structure that is NOT part of the eye. Three options belong to the eye, and one belongs elsewhere.

Explain the concept: The eye is the organ of sight. Its main parts and their functions:

• Conjunctiva: a thin, transparent membrane covering the front of the eyeball and lining the eyelids. It protects the eye and keeps it moist.
• Cornea: the transparent front part of the eye. It does most of the light refraction (bending).
• Iris: the coloured, muscular part that controls the size of the pupil and so regulates how much light enters.
• Others to remember: lens, retina, sclera, choroid, pupil, optic nerve, aqueous and vitreous humour.

The cochlea is a coiled, snail-shaped tube in the inner ear. It converts sound vibrations into nerve impulses that travel to the brain through the auditory nerve. It has nothing to do with sight.

Step-by-step solution:

1. Cochlea is in the ear (hearing), so it is not part of the eye.
2. Conjunctiva covers the eye surface, so it is part of the eye.
3. Cornea is the front transparent layer, so it is part of the eye.
4. Iris controls pupil size, so it is part of the eye.

Correct answer: A. Cochlea

Exam tip: Group structures by organ. For the ear, remember: pinna, ear canal, eardrum (tympanum), ossicles (hammer, anvil, stirrup), cochlea, semicircular canals, Eustachian tube. For the eye, remember: Conjunctiva, Cornea, Iris, Lens, Retina. If you see "cochlea" with eye parts, it is the odd one out.