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UCL Medical Retina > Unit 1 A&P > Flashcards

Unit 1 A&P Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the 5 functions of the choroid?

A

Light absorption

Thermoregulation

Nutrition to outer 1/3 of retina

Modulation of IOP via blood flow control

Drainage of aqueous flow via uveo-scleral pathway

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2
Q

Which arteries feeds the choroid?

A

Anterior and posterior ciliary arteries

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3
Q

What are the 4 layers of the choroid (outside - in)

A
  • Haller’s
  • Satler’s
  • Choriocapillaris
  • Bruch’s
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4
Q

What are the 5 layers of Bruchs (outside - in)

A
  • basement membrane of choriocapillaris
  • outer collagenous zone
  • central band of elastic fibres
  • inner collagenous zone
  • basement membrane of RPE
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5
Q

What age changes occur to Bruch’s?

A

Calcification of elastic fibres

Increased cross-linking of collagenous fibres

Increased turnover of glycosaminoglycans

Fat accumulation

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6
Q

What are the layers of the sclera? ( outside - in)

A
  • episclera
  • scleral stroma
  • lamina fusca
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7
Q

What is the ideal entry point for retinal surgery and why?

A

Pars plana as there is no overlying retina

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8
Q

What size is the macula and where is it?
What size is the optic disc?

A

5mm in diameter,
3mm temporal to OD

OD is 1.8 x 1.7 mm

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9
Q

What diameter is the fovea?

A

1.5mm

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10
Q

Which artery feeds the inner 2/3 of the retina and from where does it originate?

A

Central retinal artery which is the first branch of the ophthalmic artery.

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11
Q

What are the names of the 3 layers of capillaries that service the retina?

A

Radial (peripapillary capillaries)

Superficial capillaries in the ganglion and nerve fibre layers.

Inner nuclear layer, deep dense capillaries.

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12
Q

In which quadrant do most A/V crossings occur and why?

A

Temporally because nasal vessels tend to follow a straighter route.

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13
Q

In which patients is reduced blood flow common?

A

Glaucoma,

AMD

Diabetic retinopathy

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14
Q

What speed do retinal capillaries circulate?

A

172mls/100g retina/min

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15
Q

What speed does blood flow in the choriocapillaris?

A

1280mls blood/100g retina/min

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16
Q

How is retinal blood flow regulated?

A

Autoregulated and governed by metabolic need.

17
Q

Name the 10 retinal layers (outer - innter)

A
  1. RPE
  2. Inner and outer segments of photoreceptors
  3. External limiting membrane
  4. Outer nuclear layer
  5. Outer plexiform layer
  6. Inner nuclear layer
  7. Inner plexiform layer
  8. Ganglion layer
  9. Nerve fibre layer
  10. Inner limiting membrane
18
Q

What is the external limiting membrane made up of?

A

Fusion of muller cells

19
Q

What is the inner limiting membrane made up of?

A

Muller cell foot plates

20
Q

What is the outer nuclear layer made up of?

A

Nuclei and cell organelles of the photoreceptors

21
Q

What is the outer plexiform made up of?

A
  1. Bipolar cells (radial patter,n on or off)
  2. Horizontal cells (used in visual signal integration)
  3. Amacrine cells (modulate bipolar and photoreceptor signals)
  4. Ganglion cells
  5. Muller cells
22
Q

What is the vitreous made of?

A
  1. 99% water
  2. Hyaluronic acid
  3. Soluble proteins
  4. Ascorbic acid
  5. Type 2 collagen fibrils
23
Q

Where is vitreous attached to the retina?

A

Pars plana

Ora serrata

Optic disc

Macula Along large retinal vessels

24
Q

What are the steps the 11-cis componant of rhodopsin undergoes on exposure to light?

A
  • all trans retinal
  • all trans retinol (then moves to RPE)
  • trans retinyl esters
  • RPE65
  • cis-retinol
25
Q

Describe the activation cycle following the conversion of 11-cis retinal - all trans retinal?

A

This activates transducin which activates PDE which converts cGMP into normal GMP which closes the sodium channels.

26
Q

What is the polarity of photoreceptors in their resting state compared to normal cells and in light conditions?

A

-57mV (-78 in other cells)

27
Q

How many rods and cones are there?

A

60 million cones

120 million rods

28
Q

What are the 7 functions of the RPE

A
  1. Electrical homeostasis
  2. Cell regeneration after surgey
  3. Visual pigment synthesis
  4. Phagocytosis
  5. Maintenance of retinal adhesion
  6. Control of fluid and nutrients into the subretinal space
  7. Synthesis of growth factors i.e. VEGF
29
Q

What pigments are found in the RPE?

A

Lipofuscin

Melanin

30
Q

Where does lipofuscin come from

A

Aged or damaged photoreceptors

31
Q

Which pigment is responsible for the intrinsic fluorescence of the fundus?

A

Liposfucin

32
Q

Why is the aged fundus less pigmented?

A

Melanin is contained within melanosomes which fuse with lysosome and breakdown with age.

33
Q

Which cones respond to short, medium and long wavelengths?

A

blue, green, red

34
Q
A

UCL Medical Retina (17 decks)

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