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Block 6 > 6.2 Histology of the eye > Flashcards

6.2 Histology of the eye Flashcards

1
Q

What are the 3 layers of the eye?

A

Corneoscleral
Uveal
Retinal

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2
Q

What is the conjunctiva

A

mucous membrane which covers the exposed part of the eye (sclera and inner surface of the eyelids)

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3
Q

What is the function of the conjunctiva

A

Mucinous secretions add to the protective layer covering the eye
Allow eyelids to move freely over the eye

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4
Q

What is the histology of the conjunctiva?

A

non keratinzing stratified squamous epithelium with goblet cells and scattered melanocytes

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5
Q

What is the common presentation of conjunctiva pathology?

A

Inflammation bilaterally with a red appearance and hyperaemic vesses

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6
Q

What divides the eye into chambers?

A

The lens and iris

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7
Q

What do teh anterior and posterior chamber contain?

A

Aqueous humour

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8
Q

How does the aqueous humour circulate?

A

Produced by the ciliary processes, secreted into the posterior chamber by the ciliary body, circulates through the pupil and drains into the canal of schlemm into the anterior chamber

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9
Q

What is the function of the cornea?

A

Allow entry of light and the principle mechanism for focusing images on the retina

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10
Q

What is the junction of the cornea and sclera?

A

Limbus

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11
Q

What are the 5 layers of the cornea?

A 
Epithelium 
Bowmans membrane
Stroma 
Descemet's membrane 
Endothelium
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12
Q

What kind of epithelium is the cornea?

A

stratified squamous

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13
Q

Where does the cornea get its nutrients from?

A

The aqueous humour and environmental oxygen

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14
Q

What is ulcerative keratitis?

A

Inflammation of the cornea from a break in the epithelium

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15
Q

Does the cornea have blood vessels?

A

No

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16
Q

What is keratoconus and what causes it?

A

Bulging of the eyeball due to weak mesenchymal collagen

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17
Q

What is the role of the sclera?

A

Insertion of the extraocular eye muscles, protection and support

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18
Q

What is the histology of the sclera?

A

Dense fibrous avascular tissue which is continuous with the dura surrounding the optic nerve

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19
Q

What conditions have a thinning of the sclera?

A

connective tissue disorders such as marfans, Ehlers danlos and osteogenesis imperfecta

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20
Q

What will you see histologically in thinning of the sclera?

A

Underlying choroidal pigment shows through which will result in a blue colour (normal in newborns)

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21
Q

What is the role of the iris?

A

Regulates the amount of light coming in (aperture control), esures light enters through the pupil

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22
Q

What innervates the iris?

A

ANS

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23
Q

What is the iris made of and what are teh surfaces composed of?

A

Pigmented stromal cells
Anterior: irregular with fibroblasts and melanocytes
Posterior: Smooth pigmented epithelium

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24
Q

What determines eye colour

A

The amount of pigment in the stroma

25
Q

What are the iris muscles?

A

Dilator pupillae and Constrictor pupillae

26
Q

What orientation are the dilator and constrctor pupillae, what are the made of and what is their innervation?

A

Dilator: radially oriented made of myoepithelial cells extending from the ciliary body SYMPATHETIC

Constrictor: Circumferentially oriented, smooth muscle PARA

27
Q

What is a coloboma?

A

defect in one of teh structures of the eye

28
Q

What is CHARGE syndrome?

A 
Coloboma 
Heart defects, 
Atresia of the choanae, 
Retarded growth and development
Genital hyperplasia 
Ear abnormalaties
29
Q

What is aniridia and what causes it?

A

Absence if the iris - congenital or due to penetrating eye injury

30
Q

What is WAGR syndrome?

A

Wilms tumour
Aniridia
Genitourinary abnormalities
Retardation

31
Q

What is Mydriasis and what causes it?

A

Dilation of the pupil - darkness, autonomic neuropathy, trauma, drugs, raised ICP

32
Q

What is the ciliary body?

A

A continuous thickened ring on the inner surface of the anterior sclera that is a continuation of the choroid

33
Q

What is the function of the ciliary body?

A

Contains ciliary muscle
Permits fine focusing of images on the retina
Attaches lens via the zonules
Secrete aqueous humour

34
Q

What is the ciliary muscle and what does it do?

A

smooth muscle which inserts onto the sclera and ciliary body

controls the shape of the lens

35
Q

What is the role of the ciliary process?

A

Anchor the lens into place and form aqueous humour

36
Q

What are the two layers of epithelium of the ciliary processes?

A

Outer: non pigmented, actively transports aqueous humour

Inner: continuous with retina pigmented epithelium

37
Q

What are the zonules?

A

Fibrillin that attaches the lens to the ciliary process

38
Q

What are the layers of the lens?

A

Capsule
Subcapsular epithelium
Lens fibres

39
Q

What is the function of the lens?

A

Permits focussing on near and far objects

Accommodation in conjunction with ciliary muscles

40
Q

what happens when you focus on a near object?

A

Ciliary muscles contract causing forwards displacement of the choroid and ciliary body reliving tension on the zonules - lens will round up keeping object in focus

41
Q

What is a cataract and what does it cause?

A

Opacity of the lens causing light to be scattered and only a small amount transmitted

42
Q

What is glaucoma?

A

Raised intra-ocular pressure due to obstruction of the flow of aqueous humour

43
Q

What causes open angle glaucoma?

A

Obstruction of the drainage structures in the angle of the anterior chamber

44
Q

What causes closed angle glaucoma?

A

Narrow anterior chamber which leads to the peripheral part of the iris compressing the trabecular meshwork

45
Q

What is the function of the choroid?

A

Supplies nutrients and oxygen to all layers of the eye and absorbs light to prevent light scattering within the eye

46
Q

Where does the choroid lie?

A

Between the retina and the sclera

47
Q

Where is the vitreous and what is its function

A

Posterior compartment

Transmits light, supports the lens, holds the retina in place, contributes to intraocular pressure

48
Q

What is the function of the retina?

A

photoreception
conversion of photons into action potential
Visual processing

49
Q

What are the 3 types of cells in the retina?

A

Neurons (ganglion, bipolar, horizontal, amacrine, photoreceptors)

Pigmented epithelial cells
Neuronal support cells (Muller cells)

50
Q

How many and what are the layers of the retina?

A 
10 
Internal limiting membrane 
Nerve fibre 
Ganglion cell 
Inner plexiform 
Inner nuclear (Muller cells) 
Outer plexiform 
Outer nuclear 
External limiting membrane 
Photoreceptors 
Retinal pigmented epithelium
51
Q

Where are rods concentrated

A

outer edge of the retina

52
Q

What is the inner and outer segments of rods made of?

A

Inner: golgi and mitochondria
Outer: flattened membranous discs with rhodopsin

53
Q

What happens with rod loss?

A

Night blindness and loss of peripheral vision

54
Q

What are cones sensitive to?

A

blue red and green light

55
Q

What kind of epithelium is the retinal pigmented?

A

Columnar with basal nucleus

56
Q

What is the function of retinal pigmented epithelium?

A

Synthesis of melanin that absorbs stray light
Phagocytose shed rod discs
Support for photoreceptors

57
Q

What fibres form the optic disc?

A

non myelinated afferent fibres converge medial to the fovea

58
Q

How does the optic nerve form?

A

Non myelinated afferent fibres converge at the optic disc, penetrate the sclera through the lamina cribrosa to become the optic nerve - become myleinated fibres from the optic disc

59
Q

What is papilloedema?

A

Swollen optic nerve head secondary to raised intracranial pressure causing disc margins to be blurred but no affect on visual acuity

Block 6 (48 decks)

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