Question

Explain internal and external eye. Draw a neat and labelled diagram of a cross-section of an eye.

Answer 1

External parts are visible on the outside or form the outer protective and light-admitting layers of the eyeball:

1. Sclera: The tough, white outer layer that protects the inner parts and maintains the shape of the eye.
2. Cornea: The clear, dome-shaped front window of the eye that bends light to help focus it.
3. Iris: The colored, muscular ring behind the cornea that controls the size of the pupil.
4. Pupil: The dark central opening in the iris that lets light enter the eye.
5. Conjunctiva: A thin, clear membrane covering the sclera that lubricates and protects the eye from dust.

Internal parts lie inside the eyeball and manage the processing of light:

1. Lens: A clear, flexible structure behind the iris that fine-tunes the focus of images onto the retina.
2. Ciliary Body and Muscles: Tissue holding the lens in place that alters the shape of the lens for near or distant vision.
3. Retina: The inner light-sensitive layer packed with rods and cones that changes light into electrical signals.
4. Aqueous Humor: A clear fluid in the front chamber that nourishes the cornea and lens.
5. Vitreous Humor: A clear gel filling the back cavity that supports the shape of the eye.
6. Optic Nerve: The main nerve bundle carrying visual messages from the retina to the brain.