Retina A&P

Question 1

RPE Intercellular junctions

Answer 1

Between RPE cells

• Gap Junctions
• ZA and ZO: Terminal Bar
• Makes the RPE part of the blood-retinal barrier

Between RPE and Photoreceptors
-None! This creates a potential space, and is the location of retinal detachment. When a retinal detachment occurs, the photoreceptors are separated from nutrients supplied by the choroid, and can necrose

Question 2

Location and consequences of retinal detachment

Answer 2

Location: between RPE and photoreceptor layer

Consequence: necrosis of the neural retina due to loss of access to choroidal nutrition

Question 3

Rods vs. Cones: Pigment

Answer 3

R: rhodopsin

C: opsin’s for specific wavelengths

Question 4

Rods vs. Cones: Disks

Answer 4

R: 600-1000, seperate from membrane

C: 1000-1200, folds of membrane

Question 5

Rods vs. Cones: Terminations

Answer 5

R: spherules

C: pedicles, with lateral expansions called telondendria

Question 6

Rods vs. Cones Renewal System

Answer 6

Rods
Disks are constantly produced at the base (inner segment). Disks move through the cilium and enter the outer segment. Disks move progressively towards the tip. Disks are sloughed in the morning and pagocytosed by the RPE

Cones

• Same process
• Disks continuous, not easily separated
• Disks sloughed in the evening

Question 7

How many disks are pagocytosed by an RPE cell every day?

Answer 7

1000-2000 disks

Question 8

Myoid

Answer 8

Area of the photoreceptor inner segment that contains the golgi apparatus and endoplasmic reticulum

Question 9

Ellipsoid

Answer 9

Area of the photoreceptor inner segment that contains mitochondira

Question 10

Triad

Answer 10

Specialized junction consisting of a bipolar cell dendrite, flanked by two horizontal cell processes within an invagination of a photoreceptor terminal

Question 11

Fiber baskets (of Schultze)

Answer 11

Apical villi of Muller Cells that terminate between inner segments of photoreceptors

Question 12

Destination of P-type and M-type ganglion cells

Answer 12

P-type: parvocellular layers of the LGN

M-type: magnocellular layers of the LGN

Question 13

Extent of Muller Cells

Answer 13

Extend from photoreceptor layer (apical) to internal limiting membrane (basal)

Basically, the entirety of neural retina

Question 14

Muller Cells function

Answer 14

• Provide structural support
• Metabolize and store glycogen
• Buffer by absorbing ions and neurotransmitters
• Secrete factors that influence local blood flood and blood retina barrier

Question 15

Microglia function

Answer 15

Phagocytic, roam the retina. Increase in response to inflammation or injury

Question 16

Astrocytes

Answer 16

Absorb neurotransmitters in ganglion and nerve fiber layers

Question 17

Locations of Parafoveal and Perifoveal layers

Answer 17

Parafoveal: 0.5mm wide. Begins where INL is 12 cells thick and ganglion layer is 7 cells thick

Perifoveal: Begins where ganglion layer is 4 cells thick, and ends where it becomes 1 cell thick

Question 18

In clinic, the structure referred to as the fovea is histologically the

Answer 18

foveola

Question 19

In clinic, the structure referred to as the macula is histologically the

Answer 19

fovea

Question 20

Macular reflex results from

Answer 20

Walls of the macula (clinical definition)

Question 21

Foveal reflex results from

Answer 21

Floor of the macula (clinical definition)

Question 22

Macula Lutea diameter, location of center

Answer 22

Diameter: 5.5mm
Center Location
-3.5mm lateral
-1.0mm inferior

Question 23

Fovea diameter

Answer 23

1.5mm

Question 24

Foveola diameter, thickness

Answer 24

Diameter: 0.35mm
Thickness: 0.13mm

Question 25

Rod-Free-Area diameter

Answer 25

0.57mm

Question 26

Capillary-Free-Zone diameter

Answer 26

0.4-.05mm

Question 27

Parafoveal Area width

Answer 27

0.5mm

Question 28

Perifoveal Area width

Answer 28

1.5mm

Question 29

Optic Disk diameter

Answer 29

Horizontal: 1.7mm Vertical: 1.9mm

Question 30

Blood supply to retina layers

Answer 30

Outer layers: choriocapillaris Inner layers: retinal vessels Outer plexiform layer is thought to be fed by both

Question 31

Location of blot-and-dot hemorrhages

Answer 31

Inner Nuclear Layer

Question 32

Location of flame-shaped hemorrhages

Answer 32

Nerve Fiber Layer

Question 33

Components of the blood-retina barrier

Answer 33

Fenestrations in the choriocapillaris allow large molecules to exit into choroidal tissue, which easily pass through Bruch's membrane. ZO in the RPE prevent them from entering the retinal tissue Retinal capillaries are non-fenestrated, and have ZO in their endothelium, preventing large molecules from entering the retina

Question 34

Sequence of filling in choroidal and retinal vessels in fluorescein angiography

Answer 34

Dye is injected, series of photos are begun Within seconds, choroidal flush --> If RPE is defective, dye seeps into retina now 6-8 seconds: retinal arteries fill, core first, then outer wall Next retinal capillaries 10sec-1min: retinal veins fill, wall first, then core Leakage of vessels will be evident with dye

Question 35

Number of cones, rods, and ganglion cells in the human retina

Answer 35

Cones: 4-5 million Rods: 80-110 million Ganglion Cells: 1 million