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Neuro Block 3 > Eye histology > Flashcards

Eye histology Flashcards

1
Q

What are the 3 layers of the eye?

A
  1. corneoscleral (tunica fibrosa)

2, uvea (tunica vasculosa)

  1. retinal layer (tunica internal/nervosa)
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2
Q

What are the refractive medias of the eye?

A

cornea

lens

suspenory ligaments

aqueous humor

vitreous body

(these are all the structures light passes through to hit the retina)

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3
Q

What are the 3 chambers of the eye?

A

anterior (between cornea and iris)

posterior (between iris and lens

vitreous (vitreous body)

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4
Q

What are the 2 general portions of the corneoscleral layer of the eye?

A

cornea (makes up anterior 1/6)

sclera (posterior 5/6 = whites)

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5
Q

What are the 5 layers of the cornea?

A
  1. corneal epithelium
  2. Bowman’s membrane
  3. Substantia propria
  4. Descernet’s membrane
  5. Corneal endothelium
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6
Q

What connective tissue makes up the sclera?

A

it’s dense fibrous CT with elastic and collagenous fibers

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7
Q

What muscles insert into the sclera of the eye?

A

the tendons of extrinsic eye muscles

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8
Q

What happens to the sclera layer at the optic nerve region? What is it called?

A

it forms something like a sieve for the nerve fibers to pass through

it’s called the lamina cribrosa

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9
Q

What do you call the corneo-scleral junction?

A

the limbus

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10
Q

At the limbus, what does the corneal epithelium becomes continuous with?

A

the bulbar conjunctiva

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11
Q

What important blood vessles are located at the limbus?

A

those that supply the cornea

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12
Q

What does the corneal endothelium form at the limbus?

A

the trabecular meshwork and the canal of schlemm where the aqueous humor drains into the epsicleral veins

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13
Q

What sort of epithelium makes up the corneal epithelium?

A

stratified squamous, non-keratinizing. 5-6 cell layers thick

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14
Q

What makes up the substantia propria (90% of the cornea)?

A

transparent, regulat CT made of regularly arranged collagen

the fibrils occur in layers of lamellae, with adjacent lamellae at 90 degree angles to each other with interdigitation holding layers together

fibroblasts are located between the lamellae

glycosaminoglycans liks chondroitin, keratan and hyaluronic acid help hold the collagen together and contribute to transparency by maintainign proper water contenct

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15
Q

What are the three components of the uvea layer?

A
  1. choroid
  2. ciliary body (made of the ciliary processes and ciliary muscle)
  3. iris
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16
Q

What are the characteristics of the choroid?

A

It’s highly vascularized and pigmented

loose CT

several layers

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17
Q

Where is the ciliary body located?

A

it girdles the eye anterior to the ora serrata (triangular in shape)

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18
Q

What do the ciliary processes do?

A

form the aqueous humor

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19
Q

What are the two layers of the ciliary epithelium and what are they continuations of?

A

the deep, pigmented layer (continuation of the RPE layer of the retina)

superficial, non-pigemtned layer (a non-nervous continuation of the inner 9 layers of the retina)

20
Q

What lies at the center of the ciliary processes?

A

the stromal cores with numerous capillaries - these are probably the source of aqueous humor)

21
Q

Describe the flow of aqueous humor.

A

ciliar processes - posteior chamber - anterior chamber - trabecular meshwork - canal of schlemm - venous system

22
Q

What attaches the lens to the ciliary processes?

A

the suspensory ligaments (zonule)

23
Q

What type of muscle are the ciliary muscles?

A

smooth

24
Q

What are ciliary muscles super important for? What happens when they contract vs. relax?

A

super importnat for accommodation

contraction - releases rension on lens, so the lens is thinner - far vision (sympathetics)

relaxation - increases tension on lens - lens is fatter - near vision (parasympathetics)

25
Q

What does the iris contain?

A

endothelial surface

underlying CT (with chromatophores to determine eye color)

smooth muscle

26
Q

What is the iris’ two types of smoother muscle and what is their innervation?

A

the sphincter - parasympathetic

dilator - sympathetic

27
Q

What is the posterior layer of the iris made of?

A

it’s two rows of cuboidal cells that are heavily pigmented in everyone - regardless of eye color

28
Q

For the retina, the sensitive portion continues anteriorly only to what…

A

the ora serrata

after that it continues as non-nervous pars ciliaris

29
Q

What are the 10 layers of the retina?

A
  1. pigmented epithelium (RPE)
  2. rods and cones
  3. external limiting membrane (outer end of muller cells)
  4. outer nuclear layer (nuclei and cell bodies of rods and cones)
  5. outer plexiform layer (synapses between photoreceptors and bipolar cells)
  6. Inner nuclear layer (cell bodies and nuclei of bipolar cells, horizonal cells, amacrine cells and muller cells)
  7. Inner plexiform (synapses of bipolar onto ganglion)
  8. Ganglion cell layer
  9. Nerve fiber layer
  10. Inner limiting membrane (inner end of muller cells)
30
Q

What is the RPE responsible for?

A

It holds the pigmented portion of the rods and cones

recycles the pigment discs as they age

synthesizes melanin to absorb light after it has sensitized the receptor so that they do get saturated

vitamin A transport and esterification for forming rhodopsin

ion transport

31
Q

For the photoreceptors, what is contained in the outer segment? In the inner segment?

A

the outer segment has the pigment discs

the inner segment has all the organelles

(they’re connected by a thin structure called the cilium)

32
Q

How many rods supply each ganglion cell compared to the cones?

A

rods = 100 per ganglion

cones: 1-10 per ganglion

33
Q

Bipolar cells extend from what two layers of the retina?

A

from the outer to the inner plexiform layers

34
Q

What do the horizontal and amacrine cells likely do?

A

the horizontal cells connect groups of cones and rods together - probably integrates information from the connected cells

the amacrine cells are primarily associated with ganglion cells and their funciton is likely integration as well, but it’s poorly understood

35
Q

What is the function of the muller cells?

A

mostly supportive - they’re the retinal glial cells basically

36
Q

What is the macula lutea? How is it related to the fovea centralis?

A

it’s an area of the retinal lying directly in the optic axis, about 5 mm in diameter

in this area, the rods gradually disappear and cones become increasingly slender and numerous

the fovea centralis is at the center of the macula and it made entirely of cones - this is the area of clearest vision and greatest acuity

37
Q

Where is the blind sport of the retina?

A

the optic disc where the nerve fibers make the optic nerve - there are no photoreceptors here.

38
Q

WIthin the optic disc, what is the optic papilla and what is the physiological cup?

A

the optic paplila is the portion fo the disc that is raised slightly due to heaping up of the nerve fibers

the physiologic cup is a small central depression through which the artery and vein of the retain emerge

39
Q

What are the layers of the lens? (layers might be a bad term…makeup?)

A

the capsule is the outermost layer, made of a basal lamina; type 4 collagen - this is what the zonular fibers attach to

the subcapsular epithelium - a single layer of cells on the anterior surface

at the equator, the subscapular epithelium cells are transformed into lens fibers and move towards the center

40
Q

WHat happens to the lens with age?

A

graduall loses water and becomes less elastic, meaning the lens is less able to accommodate

41
Q

THe lens fibers located at the center are __ than those located on the periphery.

A

older

42
Q

What fibers make up the zonule?

A

thin collagen and fibrillin

43
Q

What glands are located in the eyelid?

A

sebaceous glands: meibomian (embedded in tasrsl plates) and zies (associated with hair follicles)

sweat glands (glands of Moll)

44
Q

what type of gland is the lacrimal gland?

A

compound tubuloalveolar gland (serous secreting - lots of myoepithelial cells)

45
Q
A

Neuro Block 3 (24 decks)

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