The Human Eye Flashcards
(17 cards)
What is the cornea
Dome-shaped transparent layer that is able to refract light rays into the pupil
What is the conjunctiva
A mucus membrane covering the sclera
Secretes mucus to keep the front of eyeball moist
What is the pupil
Hole in the centre of the iris allowing light to enter the eye
What is the iris
Circular sheet of muscles, consisting of two sets of involuntary muscles (cicrulcar and radial)
Also contains a pigment which gives eyes colour
What is the eyelid
Protect cornea from machenical damage
Squinting to prevent excessive light entry
Blinking to spread tears and remove dust
What is the eyelash
Shields eye from dust particles
What is the tear gland
Secrete tears to
- wash away dust particles
- keep cornea moist to dissolve oxygen
- lubricate conjunctiva, reducing friction when eyeslids move
Name all external structures of the eye
- Cornea
- Conjunctiva
- Pupil
- Iris
- Eyelid
- Eyelash
- Tear gland
Name all internal structures of the eye
Wall of eyeball has three coats
- Sclera (outermost layer)
- Choroid (middle layer)
- Retina (innermost layer)
What is the sclera
- tough white outer covering continuous with the cornea
- portect delicate inner structures from mechanical damage
- eyes muscles (recter muscles) attached to the sclera allows movement
- maintain shape of the eyeball
- place for attachment of eye muscles
What is the choroid
- black middle layer prevent internal reflection of light
- contains blood vessels and transports blood and nutrients to the the eyeball, remove metablic waste porducts from the eyeball
What is retina
- contains light sensitive cells known as photoreceptors which consists of rods and cones
- connected to the nerve fibres from the optic nerve
- images are formed on the retina and detected by the photoreceptors on the retina
Function and types of cones
Three type (contain different pigment and absorb light of different wavelengths)
- red
- blue
- green
- Responsible for coloure vision and produce sharp images
Function of rods
- stimulated by very dim light
- allow us to see in the dark (only black and white)
- contains visual purple pigment (needs vitamin A)
- visual bleached under bright light and nerve impulses cannot be transmitted to the brain
What happens in colour blindness
- not able to perceive certain colours as one or more of the cones are missing (red, blue and green)
What is the fovea
- A small yellow depression where images are focused
- contains highest concentration of cones and no rods
- allows for detailed colour vision in bright light
What is the blind spot
- point where optic nerve leaves the eye
- no photoreceptors (no cones, no rods), thus not sensitive to light
