Chapter 3: Structures of the Eyes Flashcards
The human eyeball sits in a protective, bony cavity called?
The orbit.
What does the eyelids and eyelashes protect?
The eye tissues.
Why does the blinking spreads a film of tears over the eyeball’s exposure surface?
To protect and lubricate the eye and sweep debris away.
What is The Conjunctiva?
A clear, thin mucous membrane that covers the inner surface of the eyelids and the back and sides of the eye’s outer surface.
What does The Conjunctiva do?
Keep the front surface of the eye moist and lubricated.
Why does The Conjunctiva keep the inner surface of the eyelids moist and lubricated?
So they open and close easily without friction or causing eye irritation.
What does the Conjunctiva protect the eye from?
From dust, debris and infection-causing microorganism.
What are the three layers that made up The Wall of the Eyelid?
Sclera, Choroid and Retina.
What is The Sclera?
The tough outer tissue that protects the entire eyeball.
The Sclera is also known as?
The White of the eye.
What is The Choroid?
The middle layer of the eye that contains the blood vessels that nourish the eye.
What is The Retina?
The innermost layer of light-sensitive tissue that lines the back of the eye.
The Retina converts light into what?
Into electrical impulses that travel through the optic nerve to the brain which interprets them as images.
The front one-third of the eye is divided into what?
Two chambers.
What is the Anterior chamber?
The front part of the eye between the cornea and the lens.
What is the Posterior Chamber?
Is between the iris and lens.
What fills most of the inside of the eye?
Fluid.
What are the chambers in front of the lens (anterior and posterior chambers) filled with?
With a clear, watery fluid called aqueous humor.
What does the large space behind the lens contain?
A thick, gel-like fluid called vitreous humor.
What are the two fluids that press against the inside of the eyeball and help it keep its shape?
Aqueous humor and Vitreous humor.
What is the Cornea?
A transparent, dome-shaped membrane.
Where is the Cornea located?
At the center of the front of the eye.
If the Cornea has no blood supply, from where does it obtains its nutrients?
From tears and from fluid in the anterior chamber behind it.
The cornea plays a key role in vision by helping what?
Focus the light that comes into the eye on the retina.
What happens if the image is not focused properly?
The retina makes a blurry image.
What screens out damaging ultraviolet (UV) light from the sun?
The cornea.
What protects the lens and retina from injury due to UV rays.
The Cornea.
What is the Iris?
The colored part of the eye.
What determines eye color?
Pigmentation in the front layers.
What does the eyes need to see properly?
The correct amount of light.
What is the primary job of the iris?
To regulate how much light enters the eye.
What controls how much light enters the eye?
The muscles in the iris.
During the day less light is needed and in darker conditions that does the eye do to see things clearly?
The eye will try to let in more light to see.
What is the Pupil?
The black opening in the center of the iris through which light enters the eye.
How does the muscles of the iris work?
They either contract or enlarge the pupil depending on the level of light.
What happens when bright light comes to the eye?
The pupil will contract.
What happens when there is no much light coming to the eye?
The pupil will enlarge to let in more light.
What are the Lens?
The clear part of the eye behind the iris.
what does the Lens do?
Helps to focus light on the retina, which then relays nerve impulses to the brain.
Why does the lens adjusts the eye’s focus?
To allow us to see clear up close or far away.
The ability of the lens to bend light rays so they focus on the retina is known as?
Refraction.
What does the Lens provides?
A fine-tuning adjustment to the primary focusing structure of the eye, the cornea.
