6.2 Histology of the eye Flashcards Preview

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Flashcards in 6.2 Histology of the eye Deck (59)
1

What are the 3 layers of the eye?

Corneoscleral
Uveal
Retinal

2

What is the conjunctiva

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

3

What is the function of the conjunctiva

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

4

What is the histology of the conjunctiva?

non keratinzing stratified squamous epithelium with goblet cells and scattered melanocytes

5

What is the common presentation of conjunctiva pathology?

Inflammation bilaterally with a red appearance and hyperaemic vesses

6

What divides the eye into chambers?

The lens and iris

7

What do teh anterior and posterior chamber contain?

Aqueous humour

8

How does the aqueous humour circulate?

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

9

What is the function of the cornea?

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

10

What is the junction of the cornea and sclera?

Limbus

11

What are the 5 layers of the cornea?

Epithelium
Bowmans membrane
Stroma
Descemet's membrane
Endothelium

12

What kind of epithelium is the cornea?

stratified squamous

13

Where does the cornea get its nutrients from?

The aqueous humour and environmental oxygen

14

What is ulcerative keratitis?

Inflammation of the cornea from a break in the epithelium

15

Does the cornea have blood vessels?

No

16

What is keratoconus and what causes it?

Bulging of the eyeball due to weak mesenchymal collagen

17

What is the role of the sclera?

Insertion of the extraocular eye muscles, protection and support

18

What is the histology of the sclera?

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

19

What conditions have a thinning of the sclera?

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

20

What will you see histologically in thinning of the sclera?

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

21

What is the role of the iris?

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

22

What innervates the iris?

ANS

23

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

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

24

What determines eye colour

The amount of pigment in the stroma

25

What are the iris muscles?

Dilator pupillae and Constrictor pupillae

26

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

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

Constrictor: Circumferentially oriented, smooth muscle PARA

27

What is a coloboma?

defect in one of teh structures of the eye

28

What is CHARGE syndrome?

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

29

What is aniridia and what causes it?

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

30

What is WAGR syndrome?

Wilms tumour
Aniridia
Genitourinary abnormalities
Retardation

31

What is Mydriasis and what causes it?

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

32

What is the ciliary body?

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

33

What is the function of the ciliary body?

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

34

What is the ciliary muscle and what does it do?

smooth muscle which inserts onto the sclera and ciliary body

controls the shape of the lens

35

What is the role of the ciliary process?

Anchor the lens into place and form aqueous humour

36

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

Outer: non pigmented, actively transports aqueous humour

Inner: continuous with retina pigmented epithelium

37

What are the zonules?

Fibrillin that attaches the lens to the ciliary process

38

What are the layers of the lens?

Capsule
Subcapsular epithelium
Lens fibres

39

What is the function of the lens?

Permits focussing on near and far objects
Accommodation in conjunction with ciliary muscles

40

what happens when you focus on a near object?

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

What is a cataract and what does it cause?

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

42

What is glaucoma?

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

43

What causes open angle glaucoma?

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

44

What causes closed angle glaucoma?

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

45

What is the function of the choroid?

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

46

Where does the choroid lie?

Between the retina and the sclera

47

Where is the vitreous and what is its function

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

48

What is the function of the retina?

photoreception
conversion of photons into action potential
Visual processing

49

What are the 3 types of cells in the retina?

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

Pigmented epithelial cells
Neuronal support cells (Muller cells)

50

How many and what are the layers of the retina?

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

Where are rods concentrated

outer edge of the retina

52

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

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

53

What happens with rod loss?

Night blindness and loss of peripheral vision

54

What are cones sensitive to?

blue red and green light

55

What kind of epithelium is the retinal pigmented?

Columnar with basal nucleus

56

What is the function of retinal pigmented epithelium?

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

57

What fibres form the optic disc?

non myelinated afferent fibres converge medial to the fovea

58

How does the optic nerve form?

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

What is papilloedema?

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