Histology of the eyeball Flashcards
1
Q
what are 3 tunics of the eye
A
-fibrous
-vascular
-neural
2
Q
what makes up the fibrous layer
A
-cornea
-sclera
3
Q
what makes up the vascular layer
A
-choroid
-ciliary body
-iris
4
Q
what makes up the neural layer
A
retina
5
Q
what is the cornea
A
its the transparent avascular and highly innervated anterior portion of the fibrous coat
6
Q
what are the layers of the cornea
A
-corneal epithelium
-bowman’s membrane
-stroma
-descemet’s membrane
-corneal endothelium
7
Q
what is the corneal epithelium like
A
its non keratinized stratified squamous epithelium
8
Q
the corneal epithelium has numerous what
A
free nerve endings
9
Q
what is the bowman’s membrane
A
its a homogenous non cellular layer containing type 1 collagen fibrils
10
Q
what is the thickest layer of the cornea
A
stroma
11
Q
what is the stroma composed of
A
parallel lamellae of dense collagenous C.T (200-250 layers)
12
Q
what is each lamella of the stroma composed of
A
parallel type 1 collagen fibers with long fibroblasts
13
Q
the basement membrane of the corneal epithelium rests on what
A
bowman’s membrane
14
Q
what does the bowman membrane (anterior limiting membrane) separate
A
corneal epithelium from stroma
15
Q
in the corneal stroma what is located between the layers of collagen fibers
A
flattened fibrocytes
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
17
Q
what lines the posterior surface of the cornea
A
posterior endothelium
18
Q
what does the descemets membrane (posterior limiting lamina) separate
A
the posterior endothelium and the corneal stroma
19
Q
the lateral margins of the cornea are continuous with what
A
the conjunctiva and sclera
20
Q
what is the descemets membrane
A
its a thick basement membrane
21
Q
what is the corneal endothelium
A
its a simple squamous epithelium
22
Q
what is the function of the corneal endothelium
A
-it forms the descemets membrane
-it keeps the stroma relatively dehydrated
23
Q
whats the limbus
A
its the highly vascular transition zone between the cornea and sclera
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
25
what does the sclera cover
5/6 of the fibrous tunic
26
what does the sclera proper consist of
interlacing bundles of type 1 collagen
27
whats located in the deeper regions of the sclera
melanocytes
28
what is the choroid
its the vascular pigmented posterior portion of the middle vascular tunic
29
what is the choroid composed of
loose C.T with melanocytes
30
what separates the choroid from the retina
its Bruch's membrane
31
what does the Bruch's membrane consist of
-basal laminae of the capillaries and pigmented epithelium
-elastic and collagen layers
32
what is the ciliary body
it is the anterior continuation of the choroid
33
what does the choroid surround
the lens
34
what forms the ciliary body
loose vascular and pigmented C.T that contains 3 bundles of smooth muscle cells i.e. the ciliary muscle
35
what lines the inner surface of the ciliary body
pars ciliaris retinae ( 1 row of outer pigmented columnar cells and 1 row of inner non pigmented columnar cells)
36
the ciliary bodys highly folded inner surface forms what
ciliary processes
37
what are ciliary processes
short extensions from the inner surface of the anterior 1/3 of the ciliary body towards the lens
38
what covers the ciliary processes
pars ciliaris
39
ciliary processes give attachment to what
the lens suspensory ligaments (zonular fibers)
40
what do the zonula fibers do
anchor the lens and are attached to the ciliary processes
41
what forms the zonule of zinn
the radially oriented zonular fibers
42
what are the 2 components of the iris
anterior uveal/ stroma face- made of fibroblasts and melanocytes (its non epithelial)
posterior neuroepithelial surface made up of the retina
43
the anterior uveal face of the iris consists of what
-vascularized loose connective tissue rich in melanocytes, macrophages, fibrocytes and sphincter pupillae muscle at the tip
44
what are the 2 pigmented sub layers of the posterior neuroepithelial surface
-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
45
what are the 5 layers of the iris
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
46
the posterior part of the iris is always what colour
brown
47
whats the iris like in people with brown eyes
they have pigment throughout the iris
48
whats the iris like in people with blue eyes
the iris is clear nd the brown pigment at the back of the iris appears blue after passing through sclera/cornea
49
the sphincter pupillae muscle form a circle where
at pupillary margin
50
the sphincter pupillae is under what control
parasympathetic
51
the dilator pupillae muscle is under what control
sympathetic control
52
what mediates pupillary constriction/ miosis
sphincter pupillae muscle (circular muscles)
53
whats the light pathwaywhat mediates pupillary dilation/ mydriasis
dilator pupillae muscle (radial muscles)
54
what forms the sphincter pupillae muscle
a ring of smooth muscle
55
what makes the dilator pupillae muscle
myoepithelium adjacent to the pigmented double epithelium
56
whats the light pathway
cornea> anterior segment> pupil> lens> posterior segment> neural layer of retina> pigmented retina
57
where is the lens positioned
behind the iris and between the ciliary processes
58
the ciliary muscles are under what control
parasympathetic
59
whats the lens
its a transparent, biconvex elastic and avascular structure
60
what does the lens consist of
-lens capsule
-subcapsular epithelium
-lens substance
61
what does the lens not have
blood vessels or nerves
62
what covers the anterior side of the lens
simple epithelium/ subcapsular
63
Where is the basal side of the simple (subcapsular) epithelium in the lens facing and what covers it
It’s facing the anterior and is covered by the basement membrane/lens capsule
64
whats the apical side of the subcapsular epithelium doing
ancoring the posterior lens fibers
65
whats the lens capsule
a thick,elastic basal lamina
66
what forms the lens capsule
mitotically active cells of the subcapsular epithelium
67
what inserts into the lens capsule
xonule fibers
68
cells of the subcapsular epithelium that are mitotically active only cover what
te anterior hemisphere of the lens
69
what happens as the mitotically active cells of the subcapsular epithelium divide
they gradually move towards the equator of the lens were they transform into lens fibers
70
what proteins make up the lens
filensin and crystallin ( alpha, beta and gamma)
71
what do the proteins in the lens do
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
new lens fibers are produced when
throughout life
73
what is presbyopia
decreased elasticity and power of accommodation with age
74
whats a cataract
a loss of transparency (can be caused by infections, metabolic, hereditary, trauma, uv light)
75
myoepithelial cells in the outer layer of the iris is continuous with what
retina (because they have the same embryonic origin)
76
the layer adjacent to the stroma of the iris has what
radially oriented muscular extensions which form the dilator pupillae muscle beneath the anterior layer of the retina
77
the outer non-sensory retinal pigmented epithelium is derived from where
the outer layer of the optic cup
78
the pigmented epithelium of the retina contain many what
melanin granules
79
what is the outer non sensory pigmented layer of the retina like
-has cuboidal to columnar epithelium
-has apical microvilli
-has abundance of melanin granules
80
whats the function of the pigmented epithelium of the retina
-absorbs light
-phagocytosis of membranous discs from tips of rods
-esterification of vitamin A
81
what are the layers of the retina
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
whats the visual pigment in rods and cones
R- rhodopsin
C- photopsin
83
the retina is an outgrowth of
the brain
84
where do photoreceptors sit
on pigmented layer of choroid
85
the fovea centralis is in direct line with what
lens
86
each rod and cone has what
-dendrite
-cell body
-axon
87
what forms the dendrite of rods and cones
-outer segment which contains: membranous discs, rhodopsin in rods, iodopsin in cones
-connecting stalk with modified cilium
-inner segment
88
the axon of the rod and cones synapse with what
the dendrite of bipolar neuron of inner nuclear layer
89
whats the outer limiting membrane of the retina
a region of zonula adherent junctions between muller cells and photoreceptors
90
what does the outer nuclear layer of the retina contain
nuclei of rods and cones
91
what does the outer plexiform layer of the retina contain
axodendritic synapses between the photoreceptor cells and dendrites of bipolar and horizontal cells
92
what does the inner nuclear layer of the retina contain
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
what does the inner plexiform layer of the retina contain
axodendritic synapses between axons of bipolar neurons and dendrites of ganglion cells and amacrine cells
94
what does the ganglion cell layer of the retina contain
cells bodies of large multipolar neurons of the ganglion cells
95
what does the optic nerve fiber layer of the retina contain
unmyelinated axons of the ganglion cells ( NB. these axons become myelinated as the nerve pierces the sclera)
96
what forms the inner limiting membrane of the retina
basal laminae of the muller cells
97
where does the fovea centralis lie and what does it do
center of macula lutea
responsible for visual acuity
98
what are 4 cell groups of the sensory retina
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
what happens at the optic papilla
-the optic nerve penetrates the retinal layer and leaves the eye
- the retinal blood supply enters and exists
100
whats the second blood supply system of the retina
central retinal artery and vein
101
what is the conjunctiva
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
whats the epithelium of the conjunctiva
stratified columnar epithelium with many goblet cells
103
what is the lamina propria of the conjunctiva
loose C.T
104
what requires an ophthalmologic exam
-retinal detachment
-iridodialysis
-opacified cornea
-dislocated lens
105
in an ophthalmologic exam what reveals a corneal abrasion
fluorescein
106
what does the bowmans membrane consist of
densely packed collagen fibrils embedded in ground substance
107
whats the sclera
the tough layer of dense CT (consisting of collagen fibers and elastic networks)
108
the sclera is distended by what
intraocular pressure
109
what are functions of the sclera
-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
what is the choriocapillary layer
its where there are small blood vessels in the innermost part of the choroid that supply the retina with nutrients
111
what forms the ciliary epithelium
pars ciliaris of the retina
112
the outer cell layer of ciliary body is what
pigmented
113
the inner cell layer of the ciliary body is what
non pigmented
114
What do 2 of the bundles of the ciliary muscle do
they attach to the sclera and stretch the ciliary body when they contract , which regulates the tension of the zonal e fibers
115
What does the reduced tension in the suspensory ligaments do
It results in the thickening of the lens which focuses the lens on close objects , in a process called accommodation
116
The outer non sensory retinal pigmented epithelium extends how
From optic disc to ora serrata
