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The wall of the eye consists of what layers
- Corneoscleral coat (outer)
- Uvea (middle vascular layer)
- Retina (inner photosensitive layer)
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Where is the anterior chamber of the eye
Between the cornea and the iris
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Where is the posterior chamber of the eye
Between the iris and the lens
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Where is the Vitreous chamber of the eye and what does it contain
- Between the lens and the retina
- Vitreous humor
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What does the Vitreous humor consist of
Hyaluronic acid and widely dispersed collagen fibers
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What does the Corneosclera consist of
- Sclera (white portion)
- Cornea (transparent portion)
- These layers are continuous
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What is the Sclera made of
Dense fibrous connective tissue that provides attachment for the eye muscles, and is interspersed with fibroblasts and few capillaries
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Limbus
- Area of transition from the transparent collagen bundles of the cornea to the white opaque fibers of the sclera
- "Area in Limbo"
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What are the five layers of the cornea
- Epithelium
- Bowmans capsule
- Corneal stroma
- Descemets membrane
- Endothelium
- "EBCDE"
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What type of cells are in the epithelium of the cornea
Non-keratinized stratified squamous epithelium
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What protects the cornea from UV
Ferritin
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What is in the bowmans capsule of the cornea and what is its role
- No cells, but contains collagen fibers
- Helps to prevent against infection
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What is the thickest layer of the cornea and what is it made of
- Corneal Stroma
- Collagen, elastic fibers, interspersed fibroblasts
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What secretes the Descemets membrane
Endothelium
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What kind of cells make up the Endothelium of the cornea
Simple Squamous epithelium
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What makes the cornea so sensitive
It is highly innervated
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What are the three parts of the Uvea/Vascular coat
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What is the choroid
- A highly vascularized layer that provides nutrients for the underlying retina
- It also contains connective tissue and fibroblasts
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What is in the choroid that prevents the reflection of incident light
Melanocytes, this is also what makes it black
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What is the role of the ciliary body
- It contains the ciliary muscle that helps shape the lens
- Its processes make the Aqueous humor
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The ciliary body is made up of what layers
- Outer non-pigmented layer
- Inner pigmented layer
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What happens when the ciliary muscles are contracted
- The lens becomes thicker to focus on near objects
- Relaxation makes it flatter
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What is the role of the iris
Regulation of the amount of light that enters the eye by the contraction of diaphragm muscle (colored portion of the eye)
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What determines the color of the iris
- 1. Melanin content of the iris pigment epithelium
- 2. Melanin content within the iris stroma
- 3. Cellular density of the iris stroma
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What makes the Aqueous humor, and what is made of
- Ciliary epithelium in the posterior chamber
- Similar to plasma, but much less protein
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Where can aqueous humor be found
In the anterior and posterior chambers of the eye
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What is the purpose of the aqueous humor
It provides nutrients and oxygen to the lens and cornea
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How does the aqueous humor get out of the anterior chamber
Through the canal of Schlemm directly to the venous system
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In what direction does the Aqueous humor flow
From the posterior chamber to the anterior chamber
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How much aqueous humor is drained a minute
2-3 ul through the Canal of Schlemm
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Glaucoma
Increased intraocular pressure damaging the optic nerve, often caused by excessive secretion of aqueous humor
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What is the lens of the eye made up of
- 35% Protein
- 65% Water
- Encased in collagen IV membrane
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Crystallins
Lens fibers that have lost their organelles and nuclei and are among the longest lived proteins in the body
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What is unique about the life of a lens
It keeps growing throughout life and contains the longest lived proteins in the body
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Cataracts
Then lens becomes clouded with age due to conformational changes or the cross linking of the lens proteins
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What must an image travel through before reaching the retina
- Cornea
- Aqueous humor
- Lens
- Vitreous body
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What is the chief refractive element of the eye
The Cornea
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Myopia
- Near-sighted (far objects are blurry)
- Result of the cornea being too thick or eyeball is too long
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Hyperopia
- Far-sighted (near objects are blurred) eyeball is too short
- (Hyper = focused image is beyond the retina)
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What kind of lens is used to correct myopia and hyperopia
- Myopia - Concave
- Hyperopia - Convex
- "My Opi (grandpa) lives in a cave"
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Astigmatism
Unequal curvatures so the image isn't focused in one portion on the retina
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The retina consists of what two components
- Neural retina
- Retinal pigment epithelium
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Neural retina
Top layer of the retina (closest to lens) that contains the light sensitive receptors and the complex neuronal networks
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Retinal pigment epithelium
Bottom layer of the retina composed of simple cuboidal melanin containing cells and rests on the choroid
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Where is the neural retina derived from
Inner layer of the optic cup
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What is the pigment epithelial layer of the retina derived from
Outer layer of the optic cup
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What is a detached retina
A seperation between the Neural retina and the Retinal pigment epithelium
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What provides the nutrients and metabolic support for the rods and cones
Retinal pigmented epithelium
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Rods have what role in the eye
They detect dim light (no color) and there is only one type
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What is the role of the Cones in the eye
They are specialized receptors for bright light and color
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Cones have three types to detect what colors
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Why is a detached retina bad
The neural receptors are detached from their source of nutrients from the Retinal pigment epithelium and therefore quickly die
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Fovea
- A shallow depression of the retina and is the area of greatest visual acuity
- Cell layers usually on top of the rods and cones are arranged off to the side here allowing light direct access
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Cones are highly concentrated where
In the Fovea
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Macula
A yellow pigmented zone that encircles the fovea
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Optic disk
Exit site for the optic nerve, also known as the blind spot
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Rhodopsin/Iodopsin molecules
- Molecules in the outer segments of the discs that absorb photons
- Iodopsin are in the cones
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Upon the absorption of photons in the Rhodopsin molecules what happens
Closure of Na+ channels in the plasma membrane hyperpolarizing the the membrane and reducing the rate of neurotransmitter release
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Light effects the neurotransmitters in the eye how
There is a low rate of transmitters released and the cell hyperpolarizes
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When is there a high amount of transmitter release
When it is dark
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How many Rhodopsin are there in one rod cell
30 million
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Retinal
The chromatophore of rods that is made from vitamin A
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What are the cell types in the retina, from external to internal
- Ganglion cells
- Amacrine cells
- Bipolar Neurons
- Horizontal cells
- Photoreceptors
- Muller cells (Supporting cells on sides)
- "Gangli Americans Buy Heavy Cameras from Macys"
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Axons of the bipolar cells synapse with
Dendrites of the ganglion cells
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Horizontal cells are found synapsing where
With the synaptic junctions between the photoreceptor cells and the bipolar cells modulating synaptic activity
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Amacrine cells have what function
They modulate synaptic activity connecting with axonal endings of bipolar cells and dendrites of ganglion cells
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Ganglion cells have what function
- Their axons pass to the brain in the optic nerve
- They are large and multipolar
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Muller cells have what function
(Neuroglial cells) They envelope and support the neurons and the nerve processes of the retina
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The nuclei of rods and cones are found in what layer
External nuclear layer
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Age Related Macular Degeneration (AMD)
Loss of vision in the center of the field (macula) because of damage to the retina
Leading cause of vision loss and blindness among the Americans who are over the age of 65
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Drusen
Yellow deposits of the macula that starts AMD between the retinal pigment epithelium and the choroid
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What is the difference between dry AMD and wet
Dry results from atrophy to the retinal pigment epithelial layer below the retina
Wet is caused by abnormal blood vessel growth in the choriocapillaries leading to blood and protein leakage below the macula
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