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MBBS2/Anatomy~HEAD & NECK > Histology of the eyeball > Flashcards

Histology of the eyeball Flashcards

1
Q

what are 3 tunics of the eye

A

-fibrous
-vascular
-neural

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2
Q

what makes up the fibrous layer

A

-cornea
-sclera

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3
Q

what makes up the vascular layer

A

-choroid
-ciliary body
-iris

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4
Q

what makes up the neural layer

A

retina

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5
Q

what is the cornea

A

its the transparent avascular and highly innervated anterior portion of the fibrous coat

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6
Q

what are the layers of the cornea

A

-corneal epithelium
-bowman’s membrane
-stroma
-descemet’s membrane
-corneal endothelium

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7
Q

what is the corneal epithelium like

A

its non keratinized stratified squamous epithelium

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8
Q

the corneal epithelium has numerous what

A

free nerve endings

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9
Q

what is the bowman’s membrane

A

its a homogenous non cellular layer containing type 1 collagen fibrils

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10
Q

what is the thickest layer of the cornea

A

stroma

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11
Q

what is the stroma composed of

A

parallel lamellae of dense collagenous C.T (200-250 layers)

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12
Q

what is each lamella of the stroma composed of

A

parallel type 1 collagen fibers with long fibroblasts

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13
Q

the basement membrane of the corneal epithelium rests on what

A

bowman’s membrane

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14
Q

what does the bowman membrane (anterior limiting membrane) separate

A

corneal epithelium from stroma

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15
Q

in the corneal stroma what is located between the layers of collagen fibers

A

flattened fibrocytes

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16
Q

what accounts for the transparency of the cornea

A

the regular arrangement of the collagen fibers and their small diameter in the corneal stroma

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17
Q

what lines the posterior surface of the cornea

A

posterior endothelium

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18
Q

what does the descemets membrane (posterior limiting lamina) separate

A

the posterior endothelium and the corneal stroma

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19
Q

the lateral margins of the cornea are continuous with what

A

the conjunctiva and sclera

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20
Q

what is the descemets membrane

A

its a thick basement membrane

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21
Q

what is the corneal endothelium

A

its a simple squamous epithelium

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22
Q

what is the function of the corneal endothelium

A

-it forms the descemets membrane
-it keeps the stroma relatively dehydrated

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23
Q

whats the limbus

A

its the highly vascular transition zone between the cornea and sclera

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24
Q

what does the limbus contain

A

-trabecular meshwork, which is endothelium lined spaces that lead to the canal of schlemm

-canal of schlemm, which drains the aqueous humor into the venous system

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25
Q

what does the sclera cover

A

5/6 of the fibrous tunic

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26
Q

what does the sclera proper consist of

A

interlacing bundles of type 1 collagen

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27
Q

whats located in the deeper regions of the sclera

A

melanocytes

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28
Q

what is the choroid

A

its the vascular pigmented posterior portion of the middle vascular tunic

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29
Q

what is the choroid composed of

A

loose C.T with melanocytes

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30
Q

what separates the choroid from the retina

A

its Bruch’s membrane

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31
Q

what does the Bruch’s membrane consist of

A

-basal laminae of the capillaries and pigmented epithelium
-elastic and collagen layers

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32
Q

what is the ciliary body

A

it is the anterior continuation of the choroid

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33
Q

what does the choroid surround

A

the lens

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34
Q

what forms the ciliary body

A

loose vascular and pigmented C.T that contains 3 bundles of smooth muscle cells i.e. the ciliary muscle

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35
Q

what lines the inner surface of the ciliary body

A

pars ciliaris retinae ( 1 row of outer pigmented columnar cells and 1 row of inner non pigmented columnar cells)

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36
Q

the ciliary bodys highly folded inner surface forms what

A

ciliary processes

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37
Q

what are ciliary processes

A

short extensions from the inner surface of the anterior 1/3 of the ciliary body towards the lens

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38
Q

what covers the ciliary processes

A

pars ciliaris

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39
Q

ciliary processes give attachment to what

A

the lens suspensory ligaments (zonular fibers)

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40
Q

what do the zonula fibers do

A

anchor the lens and are attached to the ciliary processes

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41
Q

what forms the zonule of zinn

A

the radially oriented zonular fibers

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42
Q

what are the 2 components of the iris

A

anterior uveal/ stroma face- made of fibroblasts and melanocytes (its non epithelial)

posterior neuroepithelial surface made up of the retina

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43
Q

the anterior uveal face of the iris consists of what

A

-vascularized loose connective tissue rich in melanocytes, macrophages, fibrocytes and sphincter pupillae muscle at the tip

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44
Q

what are the 2 pigmented sub layers of the posterior neuroepithelial surface

A

-outer pigmented layer of the ciliary body, with myoepithelial cells that form the dilator pupillae muscle anterior to it

-inner highly pigmented inner layer, that is a continuation of the retina that forms the posterior epithelium

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45
Q

what are the 5 layers of the iris

A
  1. anterior border layer- which is an incomplete layer of fibroblasts and melanocytes
  2. stroma- which a poorly vascularized C.T with fibroblasts and melanocytes
  3. vessel layer- which is well vascularized loose C.T that centrally contains sphincter pupillae muscle
  4. dilator pupillae muscle layer- which contains myoepithelial cells
  5. posterior surface layer (pigmented epithelium layer)- which is composed of 2 rows of pigmented epithelial cells which are a continuation of the pars ciliaris retinae
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46
Q

the posterior part of the iris is always what colour

A

brown

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47
Q

whats the iris like in people with brown eyes

A

they have pigment throughout the iris

48
Q

whats the iris like in people with blue eyes

A

the iris is clear nd the brown pigment at the back of the iris appears blue after passing through sclera/cornea

49
Q

the sphincter pupillae muscle form a circle where

A

at pupillary margin

50
Q

the sphincter pupillae is under what control

A

parasympathetic

51
Q

the dilator pupillae muscle is under what control

A

sympathetic control

52
Q

what mediates pupillary constriction/ miosis

A

sphincter pupillae muscle (circular muscles)

53
Q

whats the light pathwaywhat mediates pupillary dilation/ mydriasis

A

dilator pupillae muscle (radial muscles)

54
Q

what forms the sphincter pupillae muscle

A

a ring of smooth muscle

55
Q

what makes the dilator pupillae muscle

A

myoepithelium adjacent to the pigmented double epithelium

56
Q

whats the light pathway

A

cornea> anterior segment> pupil> lens> posterior segment> neural layer of retina> pigmented retina

57
Q

where is the lens positioned

A

behind the iris and between the ciliary processes

58
Q

the ciliary muscles are under what control

A

parasympathetic

59
Q

whats the lens

A

its a transparent, biconvex elastic and avascular structure

60
Q

what does the lens consist of

A

-lens capsule
-subcapsular epithelium
-lens substance

61
Q

what does the lens not have

A

blood vessels or nerves

62
Q

what covers the anterior side of the lens

A

simple epithelium/ subcapsular

63
Q

Where is the basal side of the simple (subcapsular) epithelium in the lens facing and what covers it

A

It’s facing the anterior and is covered by the basement membrane/lens capsule

64
Q

whats the apical side of the subcapsular epithelium doing

A

ancoring the posterior lens fibers

65
Q

whats the lens capsule

A

a thick,elastic basal lamina

66
Q

what forms the lens capsule

A

mitotically active cells of the subcapsular epithelium

67
Q

what inserts into the lens capsule

A

xonule fibers

68
Q

cells of the subcapsular epithelium that are mitotically active only cover what

A

te anterior hemisphere of the lens

69
Q

what happens as the mitotically active cells of the subcapsular epithelium divide

A

they gradually move towards the equator of the lens were they transform into lens fibers

70
Q

what proteins make up the lens

A

filensin and crystallin ( alpha, beta and gamma)

71
Q

what do the proteins in the lens do

A

they are responsible for the transparency and refractive properties of the lens and account for up to 60% of the mass of the lens fibers

72
Q

new lens fibers are produced when

A

throughout life

73
Q

what is presbyopia

A

decreased elasticity and power of accommodation with age

74
Q

whats a cataract

A

a loss of transparency (can be caused by infections, metabolic, hereditary, trauma, uv light)

75
Q

myoepithelial cells in the outer layer of the iris is continuous with what

A

retina (because they have the same embryonic origin)

76
Q

the layer adjacent to the stroma of the iris has what

A

radially oriented muscular extensions which form the dilator pupillae muscle beneath the anterior layer of the retina

77
Q

the outer non-sensory retinal pigmented epithelium is derived from where

A

the outer layer of the optic cup

78
Q

the pigmented epithelium of the retina contain many what

A

melanin granules

79
Q

what is the outer non sensory pigmented layer of the retina like

A

-has cuboidal to columnar epithelium
-has apical microvilli
-has abundance of melanin granules

80
Q

whats the function of the pigmented epithelium of the retina

A

-absorbs light
-phagocytosis of membranous discs from tips of rods
-esterification of vitamin A

81
Q

what are the layers of the retina

A
  1. pigmented epithelium
  2. rods and cones layer
  3. outer limiting membrane
  4. outer nuclear layer
  5. outer plexiform layer
  6. inner nuclear layer
  7. inner plexiform layer
  8. ganglion cell layer
  9. optic nerve fiber layer
  10. inner limiting layer
82
Q

whats the visual pigment in rods and cones

A

R- rhodopsin
C- photopsin

83
Q

the retina is an outgrowth of

A

the brain

84
Q

where do photoreceptors sit

A

on pigmented layer of choroid

85
Q

the fovea centralis is in direct line with what

A

lens

86
Q

each rod and cone has what

A

-dendrite
-cell body
-axon

87
Q

what forms the dendrite of rods and cones

A

-outer segment which contains: membranous discs, rhodopsin in rods, iodopsin in cones
-connecting stalk with modified cilium
-inner segment

88
Q

the axon of the rod and cones synapse with what

A

the dendrite of bipolar neuron of inner nuclear layer

89
Q

whats the outer limiting membrane of the retina

A

a region of zonula adherent junctions between muller cells and photoreceptors

90
Q

what does the outer nuclear layer of the retina contain

A

nuclei of rods and cones

91
Q

what does the outer plexiform layer of the retina contain

A

axodendritic synapses between the photoreceptor cells and dendrites of bipolar and horizontal cells

92
Q

what does the inner nuclear layer of the retina contain

A

nuclei of:
-bipolar neurons
-horizontal neurons
-amacrine neurons
-neuroglial cells (muller cells) that extend between the vitreous body and the inner segments of the rods and cones

93
Q

what does the inner plexiform layer of the retina contain

A

axodendritic synapses between axons of bipolar neurons and dendrites of ganglion cells and amacrine cells

94
Q

what does the ganglion cell layer of the retina contain

A

cells bodies of large multipolar neurons of the ganglion cells

95
Q

what does the optic nerve fiber layer of the retina contain

A

unmyelinated axons of the ganglion cells ( NB. these axons become myelinated as the nerve pierces the sclera)

96
Q

what forms the inner limiting membrane of the retina

A

basal laminae of the muller cells

97
Q

where does the fovea centralis lie and what does it do

A

center of macula lutea

responsible for visual acuity

98
Q

what are 4 cell groups of the sensory retina

A
  1. photoreceptor neurons- rods and cones
  2. conduction neurons- bipolar and ganglion cells
  3. association neurons- horizontal and amacrine cells
  4. supporting neuroglia cells- muller cells and astrocytes
99
Q

what happens at the optic papilla

A

-the optic nerve penetrates the retinal layer and leaves the eye
- the retinal blood supply enters and exists

100
Q

whats the second blood supply system of the retina

A

central retinal artery and vein

101
Q

what is the conjunctiva

A

its the transparent mucous membrane lining the inner surfaces of the eyelids ( palpebral conjunctiva) and reflecting onto the sclera of the anterior surface of the eye ( bulbar conjunctiva)

102
Q

whats the epithelium of the conjunctiva

A

stratified columnar epithelium with many goblet cells

103
Q

what is the lamina propria of the conjunctiva

A

loose C.T

104
Q

what requires an ophthalmologic exam

A

-retinal detachment
-iridodialysis
-opacified cornea
-dislocated lens

105
Q

in an ophthalmologic exam what reveals a corneal abrasion

A

fluorescein

106
Q

what does the bowmans membrane consist of

A

densely packed collagen fibrils embedded in ground substance

107
Q

whats the sclera

A

the tough layer of dense CT (consisting of collagen fibers and elastic networks)

108
Q

the sclera is distended by what

A

intraocular pressure

109
Q

what are functions of the sclera

A

-maintains the shape of the eyeball
-is the site for ocular muscle attachment
-provides a point of insertion for part of the ciliary muscle

110
Q

what is the choriocapillary layer

A

its where there are small blood vessels in the innermost part of the choroid that supply the retina with nutrients

111
Q

what forms the ciliary epithelium

A

pars ciliaris of the retina

112
Q

the outer cell layer of ciliary body is what

A

pigmented

113
Q

the inner cell layer of the ciliary body is what

A

non pigmented

114
Q

What do 2 of the bundles of the ciliary muscle do

A

they attach to the sclera and stretch the ciliary body when they contract , which regulates the tension of the zonal e fibers

115
Q

What does the reduced tension in the suspensory ligaments do

A

It results in the thickening of the lens which focuses the lens on close objects , in a process called accommodation

116
Q

The outer non sensory retinal pigmented epithelium extends how

A

From optic disc to ora serrata

MBBS2/Anatomy~HEAD & NECK (4 decks)

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