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HAE Quiz 3 > Histology of the Eye > Flashcards

Histology of the Eye Flashcards

1
Q

• What makes up the Outermost layer of the eye?

A

the fibrous tunic

• Sclera and cornea and some conjunctiva

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2
Q

Describe the sclera.

A

• Over most of the eyeball this is the sclera, which consists of dense regular collagenous connective tissue in layers.
 This provides most of the support for the eyeball (maintaining the shape of the eye).
 The rectus muscles anchor into the sclera.
 The conjunctiva covers some of the anterior sclera, although it does not cover the cornea
joins with the dura matter surrounding the optic nerve posteriorly

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3
Q

Describe the cornea

A

• The cornea is the clear part of the fibrous tunic, located anteriorly
- not covered by the conjunctiva

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4
Q

Describe the junction of the sclera and the optic nerve.

A

• The sclera joins with the dura matter surrounding the optic nerve posteriorly.

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5
Q

What are the components of the Middle/vascular layer?

A

uveal layer?
• Over most of the eye this is the choroid
• Anteriorly, the uveal layer thickens to make up most of the ciliary body and most of the iris.

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6
Q

What are the Suspensory Ligaments of the eye?

A

• The lens is anchored to the ciliary body by fibers, the suspensory (zonular) ligaments that make up the ciliary zonule.

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7
Q

What is the ciliary Zonule?

A

• is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye.

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8
Q

• Why does the Innermost layer ==> retina, have 2 layers? What are features of each layer?

A

• This is because the retina begins from the optic vesicle and optic cup.
• The outermost of these layers is pigmented, while the innermost layer is the neural retina.
• The neural retina,
 has 3 main layers, described below.
 is fairly thick, making the retina thick posteriorly.
 Anteriorly, it has an extremely thin continuation over the ciliary body and inner side of the iris. This portion does not have the typical rods and cones associated with the neural retina

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9
Q

• What makes up the Anterior chamber? What is it filled with?

A
  • cornea to iris
  • This is easily visualized from the front of the eye.
  • filled with aqueous humor
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10
Q

• What makes up the Posterior chamber? What is it filled with?

A
    • iris to [lens, zonular fibers and ciliary body]
  • is a very thin chamber
  • filled with aqueous humor
  • is harder to see and would only be visible through the iris
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11
Q

• What makes up the vitreous space? What is it filled with?

A
  • (posterior to the lens)
  • is the largest compartment
  • is filled with a proteinaceous gel, the vitreous humor
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12
Q

Is the Vitreous Humor renewed throughout life?

A

 is present from birth – it is NOT renewed or removed.

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13
Q

What aretery supplies the lens embryologically? Why is it clinically important?

A

• Embryologically, there is an artery, the hyaloid artery, that continues from the central retinal artery to supply the lens.
 This degenerates early in life but often leaves an irregularity in the vitreous that can be detected sometimes as a “floater”.

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14
Q

What are the components of the Sclera? Does it have blood vessels? What does the sclera do?

A
  • Dense regular collagenous connective tissue
  • Layers of collagen fibers with a few dark nuclei (fibroblasts) in between
  • A few blood vessels
  • Provides shape
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15
Q
  1. Sclera
  2. Cornea
  3. Choroid
  4. Ciliary body
  5. Lens
  6. Iris
  7. Aqueous humor
  8. Retina
  9. Fundus
  10. Optic nerve
A
  1. Sclera
  2. Cornea
  3. Choroid
  4. Ciliary body
  5. Lens
  6. Iris
  7. Aqueous humor
  8. Retina
  9. Fundus
  10. Optic nerve
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16
Q

What are the components of the Cornea? What are its five layers?

A
  • Is the anterior extension of the fibrous tunic and is highly specialized
  • Epithelium
  • Bowman’s Membrane
  • Stroma
  • Descemet’s membrane
  • Endothelium
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17
Q

What kind of cells make up the Epithelium? Can it regenerate?

A
  • stratified non-Keratinized squamous epithelium (5-6 cell layers).
  • Can regenerate; Basal cells undergo mitosis.
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18
Q

What kind of tissue makes up Bowman’s membrane? What is its function? Can it regenerate? What are the clinical considerations of its inability to regenerate?

A
  • thin layer of collagen CT without cells.
  • Provides strength and much shape to the cornea.
  • canNOT regenerate ==> that is why ulcerations or deep lacerations are so dangerous to corneal function
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19
Q

What kind of tissue is the Stroma? Is it organized or disorganized? What cells does it contain? Why must it remain hydrated?

A
  • comprises the majority of the cornea
  • many layers of collagen fibers.
  • Organized extremely precisely – each layer has all fibers in same direction.
  • Contains fibroblasts.
  • This layer must be hydrated properly in order to maintain transparency, a function of the corneal endothelium (5)
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20
Q

What kind of tissue is the Descemet’s membrane? What is its function?

A
  • fine collagen, very thin.

* The endothelium (layer 5) sits on it

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21
Q

What kind of tissue is the Endothelium? Does it regenerate? What is corneal opacity?

A
  • simple squamous
  • Takes energy to maintain clarity (rehydration of the Stroma). Endothelium pumps ions
  • Do not regenerate well
  • Infections or inflammations in the anterior chamber can damage the endothelium and produce corneal opacity
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22
Q

• Overall, is the cornea vascular? Where does nutrition come from? What maintains its moisture?

A

(NP-52, T548)

• is avascular ==> nutrition must come from aqueous humor and surface must be kept moist by tears

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23
Q

Can corneal opacities be corrected?

A

 Corneal opacities from scarring (alkali burns, etc) cannot be corrected except, potentially, by transplant.

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24
Q

Do corneal transplants require immuno suppression?

A

No. They are not vascularized.

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25
Q

Describe the corneal innervation

A

• only has pain nerve fibers entering the deep epithelium. These are branches of the ophthalmic nerve.

26
Q

Describe the refractory quality of the cornea. What is the clinical relevance of this?

A

• is the strongest refracting layer of the eye

 therefore, removal of several layers of stromal fibers can change vision and is the basis for Lasik surgery

27
Q

Where are corneal stem cells located? What inhibits and encourages vascular growth in the cornea?

A

• its limbus has corneal stem cells
 Constant replacement of corneal cells
 Inhibits vascular ingrowth (endostatin, restin, & ?)
 Inflammation such as due to chronic irritation from dirty contact lenses, can overcome this inhibition and result in vascular ingrowth (vascular endothelial growth factors – VEGF), which results in corneal opacity• Damage to Bowman’s layer prevents repair of abrasion

28
Q

What is the Choroid? Is it pigmented? Vascularized? If so by what? (NP-53, T547)

A
  • Forms the majority of the uveal layer (vascular tunic)
  • Is highly pigmented and highly vascularized with loose CT
  • long and short ciliary arteries and vorticose veins
  • Helps to nourish the outer part of the retina by diffusion
29
Q

What makes up most of the substance of the Ciliary body? (NP-52, T548)

A
  • mostly uveal

* The anterior part of the vascular tunic makes up most of the substance of the ciliary body and Iris

30
Q

What are the Cuboidal Cells of the ciliary body and iris? What do they do?

A

• There’s a very thin (yellow) epithelial covering derived from the retina on the inner side of both the ciliary body and iris. This epithelium has 2 layers: outer pigment and inner non-pigment
 These are cuboidal cells and are the primary cells manufacturing aqueous humor (7), the watery secretion that fills the anterior and posterior chambers.

31
Q

What kind of tissues are the Zonular Fibers that attach the ciliary muscle to the lens made of?

A
  • Ciliary muscle attached to lens by suspensory ligaments (these arise from ciliary processes)
  • Zonular fibers - oxytalan fibers (elastic) and collagen
32
Q

Explain the mechanics of focusing on a near object.

A

• Contraction of ciliary m. narrows the distance at the lens, which takes tension off ligaments.
 Since the lens is normally (in the young individual) elastic, the decreased tension in the suspensory ligaments causes the lens assumes its natural round shape, which allows the individual to focus on near objects.

33
Q

What is the innervation of the ciliary muscle? What is the nerve route?

A

The ciliary muscle is under control of parasympathetic nerve fibers from the CNIII (occulomotor).
 These nerve fibers synapse in the ciliary ganglion, and postganglionic fibers enter the eyeball with short ciliary nerves.

34
Q

What is the effect of parasympathetic nerves on the ciliary body?

A

Parasympathetics contract the ciliary body and take tension off of the suspensory ligaments, resulting in a rounder lens and closer focus

35
Q

What is presbyopia?

A

• the lens becomes less elastic with age. Therefore, even when the ciliary muscle contracts in older people, the lens cannot become round. This is the main reason for requiring bifocals and is called presbyopia.

36
Q

Is the Lens vascular? What is it attached to?

A

Attached to zonular fibers

• is avascular

37
Q

What are the 3 main components of the lens?

A
  • Capsule
  • Subcapsular epithelium
  • Lens fibers
38
Q

What are the qualities of the lens Capsule? What kind of tissue does it consist of?

A

 Anterior
 Refractile
 is actually thick basement membrane of the subcapsular epithelium (next layer) with type IV collagen

39
Q

What kind of cells does the Subcapsular epithelium consist of?

A

• simple cuboidal: only on the anterior side

40
Q

What do the Lens fibers consist of? What produces them throughout life?

A

 Form the majority (nucleus) of the lens
 They are actually long, thin, flat cells that lose their nuclei after accumulating the protein crystallin
 Produced from epithelium through life

41
Q

From center to periphery, what part of the lens is oldest? What is the clinical significance of this fact?

A

 The lens fibers at the center of the lens are the oldest and the most likely to become opaque, as in the most common form of age-related cataract.

42
Q

There are several terms used for abnormal refraction. What is hyperopia? Myopia? Astigmatism?

A
  • If light focuses behind the retina, that is termed hyperopia and the patient is said to be farsighted. That is, they can see things at distance but have difficulty up close.
  • If the rays of light converge in front of the retina that is termed myopia or nearsightedness.
  • Astigmatism refers to an irregular focus point.
43
Q

Describe the Iris. What other layers of the eye form the iris? What are dilator pupillae? Is it activated by para or sympathetic nerves?

A

• The final part of the vascular tunic or urea
• most is from middle (uveal) layer with an epithelial backing (from retina)
• Epithelial layer (from retina) with pigment
• myoepithelial (dilator pupillae)
 activated by sympathetics

44
Q

What kind of cells make up the iris?

A
  • Irregular outer layer with pigment cells and fibroblasts
  • Most of the iris is comprised of fibers and fibroblasts.
  • There are a large number of melanocytes and, depending on how much pigment they produce. one would either have brown or blue eyes
  • The fact that the majority of the iris is irregular connective tissue makes the iris quite distinctive, individual to individual.
45
Q

Which layers of the iris produce pigment? What happens if pigment is lacking in the stroma?

A

• Notice that the epithelium that is on the inner side of the iris always produces pigment. It is this pigment that appears blue when visualized through the rest of the tissue of the iris if pigment is lacking in the stroma.

46
Q

Of the Iris:
• Layer of CT with few blood vessels but pigment in macrophages
• Vascular layer; loose CT

A

Of the Iris:
• Layer of CT with few blood vessels but pigment in macrophages
• Vascular layer; loose CT

47
Q

What branch of the autonomic nervous system innervates the constrictor/sphincter pupillae?

A

parasympathetics

48
Q

Corneal and Light reflexes

What are consensual reflexes?

A

There are two important consensual (unilateral stimulation causes bilateral activation) eye reflexes

49
Q

What is the corneal reflex? What nerves are involved?

A
  • The nerve fibers in the corneal epithelium, when activated, transmit along the ophthalmic nerve into the brainstem.
  • There are connections to the facial motor nuclei which results in activation of the orbicularis oculi muscles, bilaterally.
  • This produces a protective blink response.
50
Q

What is the Light reflex? What nerves are involved?

A

light entering the eye activates the optic nerve.

• These fibers project into the brainstem and activate the oculomotor nerves BILATERALLY.

51
Q

What cells produce Aqueous humor ? How does aqueous humor travel to the anterior chamber? What are the Canals of Schlemm?

A
  • is created by the epithelial cells covering the ciliary processes on the ciliary body (4)
  • It must flow through the posterior chamber and pass the iris
  • It passes into the angle between the iris and the cornea into spaces that coalesce into canals of Schlemm (scleral venous sinus) (T548-top)
  • These communicate with veins
52
Q

What causes glaucoma?

A
  • Inadequate absorption produces glaucoma (T548-bottom)
  • if there is any obstruction in the angle between the cornea and Iris, or if there is any impediment to free movement of fluid into the sinus venosis, pressure will build up in the aqueous humor. This is the root cause of glaucoma.
  • The form of glaucoma where there is a very narrow space between the iris and cornea is termed narrow angle glaucoma and that is substantially more dangerous because of the speed with which pressure can develop.
  • Nonetheless, all forms of glaucoma can damage the neural part of the retina by increasing pressure in the eye.
53
Q

• What are the 2 layers of the retina?

A

• An inner neural layer
 Thick

• an outer pigmented layer
 Thin: consists of very thin pigmented cuboidal epithelium.
 is adjacent to the even more pigmented choroid.
• These 2 layers extend over the ciliary body and inner aspect of the iris

54
Q

What is a Retinal Detachment? Why/how can this happen (think embryology)

A
  • Because these the neural layer and the pigmented layer of the retina are not firmly attached, they can become separated.
  • This is what is termed a retinal detachment even though the condition is actually a separation between 2 layers of the retina.
  • This occurs because the retina develops as an indented optic cup. Therefore retinal detachment is simply redevelopment of the separation that was present in embryonic life.
55
Q

What are the three layers of the neuronal retina?

A 
•	From inside of the eye out, there is 
•	the ganglion cell layer
•	the bipolar cell layer 
•	the rods and cones. 
	As we will see, functionally there are inner and outer portions of the rods and cones that are important.
56
Q

What is the orra serrata? What is the pars plana? What is the clinical significance of the pars plana?

A
  • If one follows the retina towards the ciliary body, there comes a point where the rods and cones and other neural elements disappear. This is called the ora serrata.
  • Anterior to that spot, there are no more rods and cones. And this region between the ora serrata and the ciliary body is the pars plana. This is a location where a needle can be put into the eye without damaging the neural retina.
  • This location of transition can actually be visualized on the inside of the eye.
57
Q

9 & 10. Fundus and Optic nerve

• The inner aspect of the retina can be visualized with an ophthamoscope.

A

9 & 10. Fundus and Optic nerve

• The inner aspect of the retina can be visualized with an ophthamoscope.

58
Q

What is the optic disc? What is significant about this region? What is the Macula Lutea? And the Fovea Centralis?

A
  • The optic disc is where the optic nerve enters the posteromedial part of the globe.
  • There are no rods or cones in this area. Therefore it is a blind spot.
  • Blood vessels of the central retinal artery and vein radiate from the optic disk.
  • These vessels surround, but don’t enter, the macula lutea, which is the area of greatest concentration of cones.
  • At the center of this is the fovea centralis.
59
Q

what is miosis? mydriasis?

A

miosis is an excessively small pupil

mydriasis is an excessively large pupid

60
Q

what is neovascularization?

A

when blood vessels grow up to the limbus due to an deep cut on the cornea - when enough inflammation, blood vessels will grow across the limbus into the cornea - creates opacity

HAE Quiz 3 (5 decks)

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