(2.91-2.92) Eyes

What is the cornea and what does it do?

Transparent coating of the front of the eye

Protects the eye, refracts light entering the eye

What is the pupil and what does it do?

Central hole in the iris

Allows light to enter the eye

What is the iris and what does it do?

Coloured ring of muscle tissue

Alters pupil size by contracting or relaxing

What is the lens and what does it do?

transparent biconvex lens

focuses light clearly onto the retina

What is the retina and what does it do?

ring of muscle tissue

senses light

What is the suspensory ligament and what does it do?

ligament tissue

connects the ciliary muscle to the lens

What is the optic nerve and what does it do?

nervous tissue

carries verve impulses to the brain

What happens when an object is close to the eye?

• Ciliary muscles contract

• Suspensory ligaments loosen

• Lens become fatter as they are pulled less

• Light is refracted more

What happens when an object is far away from the eye?

• Ciliary muscles relax

• Suspensory ligaments contract

• Lens become thinner as they are pulled

• Light refracts less

What happens to the eye in dim light?

The pupil dilates to allow as much light into the eye as possible

• Radial muscles contract

• Circular muscles relax

What happens to the eye in bright light?

The pupil contracts to protect the retina from light.

• Circular muscles contract.

• Radial muscles relax.