The eye Flashcards
Define the eye
This is a light sensitive organ that allows us to see
What is the structure and function of the iris
It is a colored disc composed of muscle( circular and radial muscle) .
This changes the size of the pupil to control the amount of light that enters the eye.
What is the structure and function of the pupil?
It is a hole in the iris that allows light to enter the eye.
What is the structure and function of the conjunctiva
It is a thin transparent skin continuous with lining of eyelids.
It protects the cornea from scratching
What is the structure and function of the cornea
This is the cup shaped , transparent front part of the sclera.
It bends light rays to focus on the retina
What is the structure and function of the sclera
It is a tough, white fibrous coat.
It protects the eye
What is the structure and function of the ciliary muscle
Circular ring of muscle fibers.
Alters the shape of the lens during accommodation.
What is the function of the suspensory ligaments?
This attaches the ciliary body to the lens
State what the retina does and what it contains and what they do.
The retina forms images at the back of the eye.
This contains light sensitive cells.
Rod cells- works well in the dark. Found at the sides of the retina. Allows us see black and white.
Cone cells- works well in light. Found at the center of the retina. Allows us see color.
State the structure and the function of the choroid
Has black pigment to prevent reflection of light inside the eye.
Contains blood vessels to supply the retina with food and oxygen.
State the structure and function of the aqueous humor.
Colorless fluid
It keeps the eye inflated and provides nourishment.
Describe the fovea.
This is the most sensitive part of the retina. It only has come cells. Most light rays are focused here.
Describe the blind spot
This is the point where the optic nerve leaves the eye
Had No light sensitive cells
State the function of the optic nerve.
This takes electrical impulses from the retina and transmit it to the brain.
State the structure and function of the lens
Transparent, elastic, biconvex structure
Makes fine adjustments to focus light on retina
State the function of the vitreous humor
Gives the eye its shape
State 5 ways how the eye is protected and describe them.
1) orbits- sockets in the skull that protects the back of the eye
2) eyelashes - trap dust near the eye
3) conjunctiva - protects the cornea from scratching
4) eyelids - close to protect eye from dust, bright light, blinking spread tears
5) tear glands - wash away dust, keeps conjunctiva moist, contains an enzyme which kills bacteria (Lysozyme)
What happens in the eye when viewing near objects?
The lens thicken
Suspensory ligaments slacken
Ciliary muscle contract-
( when ciliary body shortens it grows towards lens which slackens suspensory ligaments)
What happens in the eye when viewing distant objects?
Lens becomes thinner
Suspensory ligaments tighten
Ciliary muscles relax
What is the effect of bright light on the eye?
Circular muscles of iris contract
Iris gets larger
Pupil size is reduced
What is the effect of dim light on the eye?
Radial muscles of iris contract
Iris becomes smaller
Pupil gets bigger
What is another name for short sight?
Describe it and how it is caused .
Also state how to correct it.
Another name is myopia.
This is when a person can see near objects but not distant objects.
It is caused by the eyeball being too long from front to back.
It can be corrected by using glasses with concave lens.
What is another name for long sight?
Describe it and how it is caused .
Also state how to correct it.
Another name is hypermetropia.
This is when a person can see distant objects but not near objects.
It is caused by the eyeball being too short from front to back.
It can be corrected by using glasses with convex lens
What is glaucoma caused by?
What do people see when they have it?
If not treated describe what happens.
How can it be treated?
Glaucoma is caused by the increase in pressure within the eye due to a blockage in the flow of aqueous humor.
It is painful and a halo is seen around objects in the visual field.
Increased pressure can damage the optic nerve which sends images to the brain therefore it can lead to permanent blindness.
Treatment - use eye drops to control pressure. Oral medication or surgery to open drainage canals ( trabecular meshwork) .
