Eye Flashcards
Conjunctiva
A delicate membrane that covers the eyelids
Special senses
Smell, taste, sight, and hearing
Sclera
White, fibrous, rubbery protective globe that has a transparent anterior part.
Cornea
Five layers of epithelial and fibrous tissue, is the chief refractive medium of the eye, focusing light rays onto the retina.
Lense
Tightly packed, encapsulated non elastic fibers derived from epithelial cells) also refracts light and, up to middle age, varied it’s shape and refractive index.
Light entering eye is focused on the retina by the Lense.
Attached to the ciliary body
Aqueous humor
Extra cellular fluid filling the eyes anterior and posterior chambers, and the more gelatinous
Vitreous humor
80% of the globes volume, function as refractive media.
Choroid
The inner surface of the posterior two
Ciliary body
The choroid thickens anteriorly as the pigmented fibromuscular ciliary body that surrounds the Lense.
Myopia
Short vision
It occurs when the parallel light rays from distant objects fail to reach the retina and instead are focused in front of it.
Therefore, distant objects appear blurry to myopic people.
Hyperopia
Far vision
It occurs when the parallel light rays from a distant objects are focused behind the retina- at least the testing eye in which the lens is flat and the ciliary muscle is relaxed
Cataracts
Result from this process cause vision to become hazy and distorted and they eventually cause blindness in the effected eye.
Risks:
Diabetes
Intense sun
Heavy smoking
Treatment:
Surgical removal
Replacement
Cataract glasses
Lacrimal glands
Are located above the lateral end of each eye.
Lacrimal canaliculi
Tears flush across the eyeball into the lacrimal sac
Nasolacrimal duct
Empties into the naval cavity
Photoreceptors
In the retina there are millions of receptor cells, the rods and cones.
Bipolar cells
Electrical signals pass from the photoreceptors via two neuron chain.
Ganglion cells
One of the two neuron chain that respond to light.
Optic nerve
Transmits nerve impulses to brain
Optic disc
What’s inside a rod and cone
The photorecetor cells are distributed over the entire retina except where the optic nerve ( composed of ganglion cell axons) leaves the eyeball: this site is called the optic disc, or blind spot.
Fovea centralis
A tiny pit that contains only cones.
Greatest visual acuity sharpest vision
Anything we wish to view critically is ficused on the fovea centralis.
Cones 3 types
Responds to vigorous blue light
Another green
Both green and red wave lengths
Red cones
When all three cones are being stimulated we see white.
Outer segment of cone
Attached to cell body
Corresponds to light- trapping dendrite, in which the discs contains the visual pigments are stacked like a row of pennies.
Visual pigments
When light strikes them, they lose their color, or are “bleached”
Regenerate pigment
Absorbption of light and pigment bleaching cause electrical changes in the photoreceptors cells that ultimately cause nerve impulses to be transmitted to the brain for visual interpretation,
Pigment regeneration ensures that you are not blinded and unable to see in bright sunlight.
Rhodopsin
The purple pigment found in rods
Formed in a union of protein (Opsin) and a modified vitamin A product (retinal)
When combined in rhodopsin retinal has a kinked shape that allows it to bind to Opsin.
But when the light strikes rhodopsin retinal straightens out and releases the protein.
Once straightened out the retinal continues its conversion until once again vitamin A
Aqueous humor
Clear watery fluid
Similar to blood plasma
Continually secreted by special area of choroid
Helps maintain intraocular pressure
It provides nutrients for the avascular lense and cornea.
If blocked pressure can start to build up. It causes glaucoma.
Aqueous humor
Is re absorbed into the venous blood through the
Sclera venous sinus
Light
When light passes from one substance to another it has s different density it’s speed changes and rays are bent, or refracted.
Light rays are bent in the eye as they encounter the cornea, aqueous humor, lense, and vitreous humor.
Convexity
The greater the lense Convexity the more it bends the light.
Accommodation
The ability to focus specifically for close objects.( less then 20 feet away)
Optic chiasma
The fibers from the medial side of each eye cross over to the opposite side of the brain.
Optic track
The fiber tracks that result from the medial side of each eye cross over to the opposite side of the brain.
Conjuntiva
The mucus membrane, lines the interior surface of the eyelid and continues over the eye.
Tarsal glands
Modified sebaceous glands.
Produce oil to help trap moisture in the eye.
Tears
Tears flow from the lacramsl glands across the eye and into the lacramil canaliculi( duct) located where the lacramal bone meets the orbit.
From here the tears go into the lacrimal sack, down the nasolacrimal duct and enter into the nasal cavity.
Inferior oblique
Causes you to elevate your eye and turn it lateral.
Inferior rectus
Depresses the eye.
Lateral rectus
Moves the eyes away from the nose.
Medial rectus
Causes you to look toward the nose.
Superior Oblique
Depressed the eye and moves it laterally.
Superior rectus
Elevates the eye.
Vascular tunic
Middle part of the eye.
Due to its high concentration of blood vessels.
4 steps/ ability to see light
Focus the light
Detect the light
Pass the detected message to brain
Interpret the image in the brain
Ciliary bodies
Ciliary bodies contain muscles that can squeeze the lens or let expand.
This allows the eye to focus on near or distant objects.
Myopia
Nearby objects in focus. Distant objects out of focus.
Hyperopia
Nearby objects out of focus. Distant objects in focus.
Iris
Colored part of the eye
Pupil
Black part of the eye
Eyelids meet
Medial and the lateral commisures
Lacrimal glands
Secrete tears; salt solution with antibacterial properties
Tarsal glands
Secrete an oily solution that protects the eye.
Conjectiva
Is the membrane that lines the eyelid and eyeball; inflammation is called conjunctivitis
Retina
Detects light
Inverted
Action potential
In the dark, rods and cones release inhibitory neurotransmitter (glutamate)
In the light, glutamate not longer released thus ‘exciting’ bipolar cells stimulate ganglion cells to form action potential.
Fova centralis
Is the area of the greatest visual acuity
At the middle of out field of vision
Contains cone cells which allow us to see color, but are activated by bright light.
Color blindness
Is a group of disorders charterized by the inability to see colors normally.
Red-green colorblindness is the most common type 5% of males, due to defects in cone cells.
Macula
Spots in the retina?
Information is transferred from the visual cortex
Visual information in the left half of your field of vision of both eyes travels to the right side of your brain.
The optic nerve and optic tract carry information from the retina to the brain crossing at the optic chiasma
Hemianopia
Is blindness in the same side of the visual field in both eyes.
