chp 8: The Human Eye [pure bio OLVL]

Sclera

Tough, white outer covering of the eyeball which is continuous with cornea
Eye muscles (rectus muscles) attached to this layer facilitates the movement of the eyeball (It contracts and shortens, pulling the eyeball)

Iris

A sheet of muscles, consisting of two sets of involuntary muscles: radial muscles & circular muscles.
Also contains a pigment which gives the eye its colour

Pupil

A hole in the centre of the iris, allowing light to enter the eye

Eyelids

Protects the cornea from mechanical damage.
Close/ squint to prevents excessive entry of light.
Blinking spreads tears over the eyes so that dust can be wiped off

Tear gland

Secretes tears to wash away dust particles and lubricate the conjunctiva, reducing friction when the eyelids move

Eyelash

Shields the eye from dust particles

Conjunctiva

A mucus membrane, covering the sclera.
Secretes mucus to keep the front of the eyeball moist .

Cornea

A dome-shaped, flexible and transparent layer that is able to refract light rays into the eye (Refracts light the most)

Sclera

Tough, white outer covering of the eyeball, continuous with the cornes

Aqueous chamber

Filled with aqueous humour, a transparent, watery fluid Aqueous humour keeps the front of the eyeball firm and refracts light into the pupil

Lens

Transparent, circular and biconvex structure.
Shape or thickness can be changed in order to refract light onto the retina

Suspensory ligament

Attaches the edge of the lens to the ciliary body It is NOT muscles (Cannot relax/ contract)

Ciliary body

Contains ciliary muscles which control the curvature and thickness of lens

Vitreous chamber

Filled with vitreous humour, a transparent jelly-like substance.
Vitreous humour keeps eyeball firm and refracts light onto the retina.

Retina

Contains light-sensitive cells known as photoreceptors, which consist rods and cones (photoreceptor cells convert light to nerve impulses).
Connected to nerve fibers from the optic nerve

Fovea (yellow spot)

A small yellow depression where images are focused and is where the sharpest image is seen.
Enables a person to have detailed colour vision.

Choroid

Black pigmented layer which prevents the internal reflection of light.
Contains blood vessels that carry oxygen and nutrients to eyeball and remove metabolic waste products from the eyeball

Blind spot

Region where the optic nerve leaves the eye. Does not contain photoreceptors, therefore not sensitive to light • Transmits impulses to the brain when photoreceptors are stimulated

Optic nerve

Transmits impulses to the brain when photoreceptors are simulated