2.91-2.92 Structure of the eye

G name and function

Cornea - Transparent outer part of the eye, it refracts light to reach the retina

F name and function

Pupil - Dark circular opening in the centre of the eye which lets light through

D name and function

Iris - Coloured ring of tissue which controls the amount of light entering the eye by changing the size of the pupil

E name and function

Lens - Biconvex transparent disc situated behind the iris that focuses light on the retina

C name and function

Ciliary muscle- changes the lenses shape to focus on objects at different distances (accomodation)

B name and function

Retina - the inner layer of the eye containing light receptors, rods (light) and cones (colour)

A name and function

Optic nerve - carries impulses between the eye and the brain

I name and function

Sclera- Tough outer coat of the eye

H name and function

Suspensory ligament- connects the ciliary muscles to the lens, tighten or loosen to change the lens’ shape (accomodation)

What is the conjunctiva and function?

A thin clear membrane that protects and lubricates the eye - preventing dryness, irritation and infection

What do rods and cones do?

They convert light into electrical signals for the brain

Rods: detect light intensity, enabling night vision

Cones: detect colour (red, green, blue) and fine detail in bright light

Fovea

A small depression in the centre of the retina where a high concentration of cone cells can be found

Blind spot

The one area of the retina where an image cannot be formed as there are no rods or cones; this is where the optic nerve leaves the eye

How does the eye adapt to bright light?

The circular muscles contract and radial muscles relax to make the pupil smaller (constriction), avoiding damage to the retina

How does the eye adapt to dim light?

The circular muscles relax and radial muscles contract to make the pupil larger (dilation), so more light can enter to create a better image

Accommodation

The changes that take place in the eye which allow us to see objects at different distances

How does the eye accommodate for distant vision?

Ciliary muscles relax, suspensory ligaments tighten, lens pulled flat and thin, resulting in less light refraction and focusing on far objects

How does the accommodate for near vision?

Ciliary muscles contract, suspensory ligaments loosen, lens thickens and more curved/convex, resulting in more light refraction and focusing on near objects.