The Human Eye Flashcards
Cornea
√ dome shaped transparent layer
√ refracts light rays into eye
Conjunctiva
√ mucus membrane covering sclera
√ produces mucus to keep front of eyeball moist
Eyelid
√ projects cornea from mechanical damage
√ squinting prevents excessive entry of light into eye which may damage retina
√ blinking spreads tears over eyes so that dust can be wiped off
Pupil
√ hole in centre of iris
√ allows entry of light into eye
√ size controlled by iris muscles
Iris
√ contains pigment which gives eye color
√ circular sheet of involuntary antagonistic muscles
Tear gland
Secretes tears to:
√ wash away dust particles
√ moisten cornea for absorption of dissolved oxygen
√ lubricate conjunctiva to reduce friction when eyelids move
Eyelash
shields eye from dust particles
Sclera
√ tough, white outer covering of eyeball continuous with cornea
√ eye muscles attached to sclera facilitates movement of eyeball
Choroid
√ black pigmented middle layer of eyeball
√ prevents internal reflection of light
√ contains blood vessels that carry oxygen and nutrients to eyeball
√ remove metabolic waste products from eyeball
Retina
√ innermost layer of eye wall containing light-sensitive cells/photoreceptors
Functions of cones
( red, blue, green )
√ work together to enable us to see variety of colors in bright light
√ blind person lacks certain cones in retina
Functions of rods
√ stimulated by dim light
√ contain pigment called visual purple
√ visual purple bleaches when exposed to bright light and impulses cannot be sent to brain
Fovea/Yellow spot
√ small yellow depression where images are focused
√ contains cones only
√ enables person have detailed color vision in bright light
Blind spot
does not contain photoreceptors hence not sensitive to light
Optic Nerve
transmits nerve impulses to brain when photoreceptors stimulated
