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FoundSci Unit 7 > Eye II > Flashcards

Eye II Flashcards

1
Q

What are the different subdivisions of the retina?

A

Inner vs. Outer:
Retinal pigment epithelium
Neural Retina

Anterior vs. Posterior:
Photosensitive Retina
Nonphotosensitive retina

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2
Q

What are the characteristics of the retinal pigment epithelium?

A

Outermost layer of the retina

Develops from outer layer of optic cup

Simple cuboidal epithelium

Attached through Bruch’s membrane to the choriocapillary layer of the choroid but is only loosely attached to the rest of the retina

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3
Q

What are the characteristics of the neural retina?

A

Consists of the remaining 9 layers of the retina

Contains photosensitive cells and a variety of other neurons

Develops from inner layer of optic cup

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4
Q

What are the characteristics of the photosensitive retina?

A

Area posterior to ora serrata

Ora serrata is a zig zag line that marks anterior limit of the choroid and visual retina

Contains all layer of neural retina including rods and cones (photosensitive cells)

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5
Q

What are the characteristics of the nonphotosensitive retina?

A

Area anterior to the ora serrata

Made up of two layers of cuboidal cells, does not includes rods and cones

Continuous with ciliary epithelium and pigment epithelium of iris

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6
Q

What is the structure of the retina?

A

10 layers

Photosensitive cells in outer layer

Optic nerve fibers in inner layer

Light must pass through all layers of the retina to reach rods and cones

Nerve impulses are passed back through layers to optic nerve fibers in inner layer

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7
Q

What are the major features of the retina?

A

Fovea centralis

Macula lutea

Optic disc

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8
Q

What are the characteristics and function of the fovea centralis?

A

Point of greatest visual acuity - allows maximal light penetration

Contains highest density of cone cells in the retina and has no rod cells

Conducting and association neurons are deflected at fovea to allow light to reach the cones unimpeded

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9
Q

What are the characteristics and function of the macula lutea?

A

Yellow region surrounding fovea

Ganglion cell layer thickest in this region

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10
Q

What are the characteristics and function of the optic disc?

A

Blind spot - no photoreceptors or photoreceptive cells

Where optic nerve pierces the retina

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11
Q

What does the central artery and vein of the retina do and where does it enter and travel?

A

Enters at optic disc

Travels with optic nerve fiber layer

Supplies inner layer of retina

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12
Q

Where are the photosensitive cells located in the retina? What does that mean for the cells and nerve fibers?

A

Located outside the neural retina, close to the choroid

Therefore light must travel all layers of the retina before it reaches the photosensitive cells and nerve impulse must be transmitted back through all the layers to the optic nerve fibers on the inner surface of the retina

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13
Q

How is the blind spot made at the optic disc?

A

Because the optic nerve fibers begin on the inner surface of the retina, they must pierce the retina to reach the brain, deflecting photosensitive cells and creating a blind spot

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14
Q

What are the 4 types of cells of the neural retina? What do each of them do?

A

Association neurons - horizontal and amacrine, regulate neural impulses

Conducting neurons - bipolar and ganglion, transmit visual information towards visual centers of the brain

Supporting cells - Muller’s cells, provide structural support to the retina

Photosensitive cells - rods and cones, react with light

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15
Q

What are the 10 layers of the retina from outside to inside?

A
  1. Retinal Pigement Epithelium
  2. Rods and Cones
  3. Outer limiting membrane
  4. Outer nuclear layer
  5. Outer plexiform layer
  6. Inner nuclear layer
  7. Inner plexiform layer
  8. Ganglion cell layer
  9. Optic nerve fibers
  10. Inner limiting membrane
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16
Q

What are the characteristics and function of the retinal pigment epithelium?

A

Simple cuboidal epithelium

Microvilli surround rods and cones and contain melanin granules

Strongly attached to Bruch’s membrane of choroid

Functions:
Melanin absorbs light and prevents reflection
Maintains blood-retina barrier
Phagocytosis and disposal of shed discs from rods and cones
Stores and supplies photosensitive cells with vitamin A

17
Q

What are the characteristics and function of layer of rods and cones?

A

Outer segment of photosensitive cells - Contains specialized dendrites, site of photosensitivity, contains mostly rods and some cones

Inner segment - organelles, mitochondria, RER, golgi

Rods and Cones function on diff flashcard

18
Q

What are the characteristics of the rods?

A

Most numerous

Most sensitive to light - activated in low light and inactive in full light

Discs separated from plasma membrane

Visual pigment rhodopsin reacts with light and depends on vitamin A

Insufficient uptake of vitamin A results in night blindness

19
Q

What are the characteristics and functions of the cones?

A

Less numerous except in fovea

Sensitive to color

Only active in well lit conditions and inactive in low light

Three types of cone cells - Long (red), Medium (green), and short (blue)

Discs connected to plasma membrane

Outer segment is conical and contains photopsin that reacts with light

20
Q

What is the outer limiting membrane?

A

Not true membrane

Apical border of Muller’s cells

21
Q

What is the outer nuclear layer?

A

Nuclei of the photosensitive cells

22
Q

What is the outer plexiform layer?

A

Cell processes of photosensitive, bipolar, and horizontal cells

23
Q

What are the characteristics of the inner nuclear layer?

A

Nuclei of bipolar, horizontal, amacrine, and Muller’s cells

Bipolar cells - conducting neurons

Horizontal cells - association neurons, facilitate/inhibit transmission of impulses

Amacrine cells - regulate which impulses are transmitted to brain via the optic nerve

Muller’s cells - supporting cells, cytoplasm spans thickness of neural retina

24
Q

What is the inner plexiform layer?

A

Processes of bipolar, ganglion, and amacrine cells

25
Q

What is the ganglion cell layer?

A

Ganglion cell nuclei - conducting neurons and form optic nerve

Layer varies in thickness - thickest in macula lutea and absent in fovea centralis

Hyperpolarization of rods and cones causes depolarization of ganglion cells sending action potentials through axons into the brain

26
Q

What is the layer of optic nerve fibers?

A

Axons of ganglion cells form the optic nerve

Converge and pierce the retina at the optic disc

Central retinal artery travels within this layer from ophthalamic artery and supplies inner layers of retina

27
Q

What is the inner limiting membrane?

A

Basal lamina of the Muller’s cells

Separates retina from vitreous body

28
Q

What is the path of visual processing in the retina? 7 steps

A
  1. Rods and cones react to light
  2. Pass info to bipolar cells
  3. Horizontal cells inhibit transmission of bad data
  4. Bipolar cells pass info to ganglion cells
  5. Amacrine cells inhibit transmission of bad data
  6. Central processes of ganglion cells form optic nerve to transmit visual info to the brain for further processing
  7. Muller’s cells provide structural and metabolic support for other retinal cells, form inner and outer limiting membranes
29
Q

What is a summary of what is in each of the 10 layers of the neural retina?

A
  1. Retinal Pigment Epithelium - NOT neural retina
  2. Rods and cones - outer segments of photosensitive cells
  3. Outer limiting membrane - apical border of Muller’s cells
  4. Outer nuclear layer - nuclei of photosensitive cells
  5. Outer plexiform layer - processes of photoreceptive, bipolar, and horizontal cells
  6. Inner nuclear layer - nuclei of bipolar, horizontal, amacrine, and Muller’s cells
  7. Inner plexiform layer - processes of ganglion, bipolar, and amacrine cells
  8. Ganglion cell layer - nuclei of ganglion cells
  9. Optic nerve fibers - processes of ganglion cells
  10. Inner limiting membrane - basal lamina of Muller’s cells
30
Q

What is age related macular degeneration?

A

Loss of photoreception localized to macula lutea leading to loss of the center of the visual field

Dry AMD - most common and caused by build up of drusen between RPE and Bruch’s membrane and within Bruch’s membrane. Separation of RPE and Bruch’s leads to degeneration of RPE and loss of vision

Wet AMD - progression of dry AMD, development of new blood vessels in choriocapllary layer of choroid, and new vessels leak fluid and blood between RPE and Bruch’s membrane

31
Q

What is retinal detachment?

A

Separation of neural retina from RPE, specifically between RPE and layers of rods and cones

RPE more strongly attached to Bruch’s membrane than to layer of rods and cones due to development. RPE derived fro outer layer of optic cup and neural retina derived from inner layer of optic cup. Come together when development but don’t form a firm connection

Can be due to trauma such as a strong blow to head or disease

32
Q

How does colorblindness occur?

A

Defects in genes encoding cones cause colorblindness

Red-green is most common

2 types of Red-Green - both sex linked and involve genes on the X chromosome

Deuteranopia - most common red-green colorblindness, loss of M cones (green deficient)

Protanopia - loss of L cones (red deficient)

Tritanopia - uncommon, loss of S cones (blue deficient), autosomal on chromosome 7, males and females affected

FoundSci Unit 7 (14 decks)

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