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Ocular Physiology 2 > Retina > Flashcards

Retina Flashcards

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
Q

How long are the rods? what does the outer segment consist of?

A

40-60 micrometers. Outer segment consists of rhodopsin which has 600-1000 stacked units called lamellae

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26
Q

At what rate are they formed? When does sloughing off occur? When do they get renewed

A

1 -5 per hour. Sloughed off In the morning. Rod lamellae can be completely renewed after 1-2 weeks.

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27
Q

T/F Sensation is the same for all wavelengths of light

A

True

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28
Q

How many bipolar cells do several rods connect with to produce a convergence

A

1 bipolar cell

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29
Q

Where are the outer segments of cones located

A

attached to the cell membrane

30
Q

What is the cone pigment called

A

Conopsin/Iodopsin

31
Q

When does slouging off of cones occur

A

In the night

32
Q

What are the 3 categories of photopigments that they are most sensitive to?

A
  1. Blue: short wavelength
  2. Green: medium wavelenth
  3. Red: long wavelength
33
Q

Where is rhodopsin more prevalent in

A

Optic disc. Rhodopsin has Vitamin A

34
Q

What is the sequence of visual transduction. (how light energy is converted)

A
  1. Rhodopsin
  2. Bathorhopsin
  3. Metarhodopsin
  4. All trans retinal
  5. Opsin
  6. 11 cis retinal
35
Q

What is Tay-Sachs Disease

A

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
Q

What is there an accumulation of in Tay sachs disease

A

GM2 in the retina, and ganglion cells degenerate…you get a cherry red spot in macular

37
Q

Vitamin A belongs to which class of lipids

A

Isoprenoid. Also called a fat-soluble vitamin. Gets stored in liver and fatty tissue

38
Q

What forms rhodopsin

A

The linkage between 11 cis Vitamin A aldehyde (retinal) + opsin

39
Q

What are the chemical forms of Vitamin A

A
  1. Retinyl ester
  2. Retinol
  3. Retinal
  4. Retinoic acid
40
Q

Which chemical form of Vitamin A is used for storage

A

Retinyl ester

41
Q

Which chemical form of Vitamin A is used for Transport and hormonal role

A

Retinol

42
Q

Which chemical form of Vitamin A is used for visual transduction

A

retinal

43
Q

Which chemical form of Vitamin A is used for synthesis (formation of glycoproteins)

A

retinoic acid

44
Q

What are chylomicra

A

Transport complexes that are compatible with the aqueous environment of the bloodstream. It goes specifically to the liver

45
Q

Which two proteins does Vitamin A (retinol) need to bind to for mobilization

A
  1. Retinol binding protein (RBP) inside the cell

2. Prealbumin (PA) in bloodstream

46
Q

What is the first step of Vitamin A deficiency

A

Nyctalopia; loss of night vision

47
Q

What is the second step of vitamin a deficiency

A

Xerophthalmia: Dry eyes; hardening of the corneal conjunctival epithelium with loss of conjunctival secretions

48
Q

What is the third step of vitamin A deficiency

A

Keratomalacia: Degeneration of the corneal epithelium, could cause corneal perforation

49
Q

What happens with Vitamin A excess

A
  1. Abdominal pain
  2. blurred vision
  3. Drowsiness
  4. Headache
  5. Irritability
  6. Nasuea
  7. Vomiting
50
Q

What is Vitamin A a treatment for

A

Retinitis pigmintosis; deficiency in night vision

51
Q

What are two biochemical aspects of Vitamin A taken in excess

A
  1. Increased gluconeogenesis

2. Protein turnover

52
Q

T/F Rods make more direct synapsed with bipolar cells

A

False! Cones do, but fewer cones are connected to a single bipolar cell

53
Q

How many rods are there? How about cones?

A

110-125 million rods

6.5 million cones

54
Q

What is the function of the Outer Limiting Membrane

A

Support network to hold the photoreceptors together

55
Q

T/F The outer limiting membrane is a real membrane

A

False! Not a real membrane…its an outcrop of muller’s connective tissue fibers

56
Q

What is the function of the outer plexiform layer

A

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
Q

What does the inner nuclear layer contain

A 
Cell bodies from:
Bipolar cells
Horizontal cells
Amacrine cells
interplexiform cells
mueller's connective fibers
58
Q

This layer is formed by the bodies of the cells found in the inner nuclear layer

A

Ganglion cell layer. Its about 10 cells deep in the macula

59
Q

What is picked up by magno cells in the ganglion cell layer?

A

They detect motion. Their axons are thick and carry rapid impulses 90%

60
Q

What are konio cells

A

The color cells (Take color information with the blue yellow pathway) 9%

61
Q

What are parvo cells

A

80% cells of the retina. The majority of cells in the retina. Information obtained

62
Q

What is the nerve fiber layer

A

Includes ganglion cell axons. these carry nervous impulses via the optic nerve to the lateral geniculate nucleus

63
Q

What are the fibers in the nerve fiber layer enveloped by

A

Extensions of muellers fibers and astrocytes

64
Q

What are the two types of retinal glial cells

A

astrocytes and microglia

65
Q

Where are astrocytes found and what is their function

A

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
Q

What are microglia

A

Small connective cells that proliferate for phagocytosis where damage is present

67
Q

Where does the retina gets its blood supply from

A

Central retinal artery

68
Q

At the optic disc how are the main retinal vessels divided

A

Into superior and inferior branches which divide into nasal and temporal branches. There are no anastomes

69
Q

Where is the capillary network the densest

A

Densest near the macula, and absent at the fovea and lacking in a small area behind the ora serrata

70
Q

Where does the central retinal vein exit

A

At the optic disc

Ocular Physiology 2 (8 decks)

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