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Ocular Physiology 2 > Retina > Flashcards

Retina Flashcards

(70 cards)

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1
Q

By how much does the retina extend over the posterior globe

A

2/3

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2
Q

What is it internally bound by? What about externally?

A

Internally: vitreous body
Externally: Bruch’s membrane of choroid

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3
Q

What color is the retina? What about after death?

A

Reddish because of rhodopsin. Grays/opacifies after death

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4
Q

What are the two main functions of the retina and what structures are responsible for it?

A
  1. Detect light and movements: Rods

2. Color and vision form (central visual field):Cones

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5
Q

What are the rods and cones named after?

A

Their outer segments; Rods have a rod like appearance, cones haves conical shaped outer segments

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6
Q

Where is the retina thinnest? Where is it thickest?

A

Thinnest centrally and peripherally: optic disc

Thickest: near macula

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7
Q

What refers to the internal background of the eye

A

Fundus oculi

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8
Q

What color is the fundus oculi and why?

A

Reddish/orange because of the choroidal vessels and RPE

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9
Q

What color is the fundus of a person who is dark skin, fair, skin, and albino?

A

Dark skin: darker, gray fundi
Fair skin: Lighter fundi
Albino: Can see choroidal vessels..they are devoid of pigment; extremely photophobic

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10
Q

Where does the optic nerve leave the eye and where is it located?

A

At the optic disc/papilla. Located 3mm medially and slightly above the posterior pole

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11
Q

T/F the optic disc has photoreceptors

A

False; optic disc is devoid of photoreceptors. Its projection into space produces the blind spot

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12
Q

Where is the fovea centralis located?

A

Temporal to and below the posterior pole (1-2 mm in diameter)

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13
Q

What does retinal thinning do to fovea centralis?

A

It makes a shallow depression in the surface and nerve elements are heaped around to form Henle’s layer

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14
Q

What is the foveola? How big is it?

A

It is in the fovea, and it only contains cones. 0.35 mm in diameter

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15
Q

What is the macula lutea?

A

Yellow spot, that has a yellowish pigment because xanthophyll is found here

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16
Q

What is the function of the ora serrata. Where does it lie?

A

It is a notched line which separates the neural part of the retinal periphery from the ciliary body. It lies 8.5 mm behind the limbus and 6 mm in front of the equator

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17
Q

Arteries are ____ and veins are _____

What are the normal artery to vein ratio?

A

thinner and lighter. veins are thicker and darker. No anastomoses should be present. 2:3

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18
Q

T/F Fovea should contain vessels

A

False! No vessels should be present

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19
Q

What are the four subdivision in the retina

A
  1. Pigment epithelial layer
  2. Photoreceptor Layer
  3. Intermediate Cell Layer
  4. Ganglion Cell Layer
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20
Q

What is the function of the RPE? Where is it attached?

A

Absorbs scattered light. Doesnt multiply (no mitosis) When the cell dies, neighboring cell occupies the space. It’s attached to Bruch’s membrane. There are about 5 million in each eye

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21
Q

How many photoreceptors is the pigment epithelium in contact with?

A

45 photoreceptors

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22
Q

Less obvious functions of RPE

A

Provide slow disintegration, a role in phagocytic activity

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23
Q

T/F There is a connection between the RPE and receptors

A

False!

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24
Q

What type of cells are the photoreceptors and how are they arranged

A

Sensory cells; transform light into electrical energy by chemical processes. They have a palisade arrangement (held in place by the external limiting membrane)

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25
How long are the rods? what does the outer segment consist of?
40-60 micrometers. Outer segment consists of rhodopsin which has 600-1000 stacked units called lamellae
26
At what rate are they formed? When does sloughing off occur? When do they get renewed
1 -5 per hour. Sloughed off In the morning. Rod lamellae can be completely renewed after 1-2 weeks.
27
T/F Sensation is the same for all wavelengths of light
True
28
How many bipolar cells do several rods connect with to produce a convergence
1 bipolar cell
29
Where are the outer segments of cones located
attached to the cell membrane
30
What is the cone pigment called
Conopsin/Iodopsin
31
When does slouging off of cones occur
In the night
32
What are the 3 categories of photopigments that they are most sensitive to?
1. Blue: short wavelength 2. Green: medium wavelenth 3. Red: long wavelength
33
Where is rhodopsin more prevalent in
Optic disc. Rhodopsin has Vitamin A
34
What is the sequence of visual transduction. (how light energy is converted)
1. Rhodopsin 2. Bathorhopsin 3. Metarhodopsin 4. All trans retinal 5. Opsin 6. 11 cis retinal
35
What is Tay-Sachs Disease
Results in the absence of hexaminodase A enzyme, which normally catalyzes the breakdown of ganglioside molecules as new molecules are synthesized. A partially degraded ganglioside that accumulates in neural, ocular and other tissues
36
What is there an accumulation of in Tay sachs disease
GM2 in the retina, and ganglion cells degenerate...you get a cherry red spot in macular
37
Vitamin A belongs to which class of lipids
Isoprenoid. Also called a fat-soluble vitamin. Gets stored in liver and fatty tissue
38
What forms rhodopsin
The linkage between 11 cis Vitamin A aldehyde (retinal) + opsin
39
What are the chemical forms of Vitamin A
1. Retinyl ester 2. Retinol 3. Retinal 4. Retinoic acid
40
Which chemical form of Vitamin A is used for storage
Retinyl ester
41
Which chemical form of Vitamin A is used for Transport and hormonal role
Retinol
42
Which chemical form of Vitamin A is used for visual transduction
retinal
43
Which chemical form of Vitamin A is used for synthesis (formation of glycoproteins)
retinoic acid
44
What are chylomicra
Transport complexes that are compatible with the aqueous environment of the bloodstream. It goes specifically to the liver
45
Which two proteins does Vitamin A (retinol) need to bind to for mobilization
1. Retinol binding protein (RBP) inside the cell | 2. Prealbumin (PA) in bloodstream
46
What is the first step of Vitamin A deficiency
Nyctalopia; loss of night vision
47
What is the second step of vitamin a deficiency
Xerophthalmia: Dry eyes; hardening of the corneal conjunctival epithelium with loss of conjunctival secretions
48
What is the third step of vitamin A deficiency
Keratomalacia: Degeneration of the corneal epithelium, could cause corneal perforation
49
What happens with Vitamin A excess
1. Abdominal pain 2. blurred vision 3. Drowsiness 4. Headache 5. Irritability 6. Nasuea 7. Vomiting
50
What is Vitamin A a treatment for
Retinitis pigmintosis; deficiency in night vision
51
What are two biochemical aspects of Vitamin A taken in excess
1. Increased gluconeogenesis | 2. Protein turnover
52
T/F Rods make more direct synapsed with bipolar cells
False! Cones do, but fewer cones are connected to a single bipolar cell
53
How many rods are there? How about cones?
110-125 million rods | 6.5 million cones
54
What is the function of the Outer Limiting Membrane
Support network to hold the photoreceptors together
55
T/F The outer limiting membrane is a real membrane
False! Not a real membrane...its an outcrop of muller's connective tissue fibers
56
What is the function of the outer plexiform layer
Made up of photoreceptor axons and the synapses they form with bipolar cell dendrites. Also where there are connections between horizontal cells and photoreceptor synapses
57
What does the inner nuclear layer contain
``` Cell bodies from: Bipolar cells Horizontal cells Amacrine cells interplexiform cells mueller's connective fibers ```
58
This layer is formed by the bodies of the cells found in the inner nuclear layer
Ganglion cell layer. Its about 10 cells deep in the macula
59
What is picked up by magno cells in the ganglion cell layer?
They detect motion. Their axons are thick and carry rapid impulses 90%
60
What are konio cells
The color cells (Take color information with the blue yellow pathway) 9%
61
What are parvo cells
80% cells of the retina. The majority of cells in the retina. Information obtained
62
What is the nerve fiber layer
Includes ganglion cell axons. these carry nervous impulses via the optic nerve to the lateral geniculate nucleus
63
What are the fibers in the nerve fiber layer enveloped by
Extensions of muellers fibers and astrocytes
64
What are the two types of retinal glial cells
astrocytes and microglia
65
Where are astrocytes found and what is their function
Astrocytes are found in the ganglion and nerve fiber layer. They have short and long projections that extend in all directions and promote movement from and to the vascular system.
66
What are microglia
Small connective cells that proliferate for phagocytosis where damage is present
67
Where does the retina gets its blood supply from
Central retinal artery
68
At the optic disc how are the main retinal vessels divided
Into superior and inferior branches which divide into nasal and temporal branches. There are no anastomes
69
Where is the capillary network the densest
Densest near the macula, and absent at the fovea and lacking in a small area behind the ora serrata
70
Where does the central retinal vein exit
At the optic disc

Ocular Physiology 2 (8 decks)

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