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A&P > Uvea - iris > Flashcards

Uvea - iris Flashcards

1
Q

What is the middle layer of the eye?

A

The Uvea

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2
Q

What are the three regions the uvea is composed of?

A
  • the iris
  • ciliary body
  • choroid
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3
Q

Why is the uvea sometimes called the vascular layer?

A
  • the choroid is made up of mainly blood vessels that supply the outer retinal layers
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4
Q

Where is the center aperture of the pupil located?

A
  • slightly nasal and inferior to iris center
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5
Q

what’s the range is pupil size?

A
  • 1mm to 9mm
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6
Q

When is the pupil miotic?

A
  • in brightly lit conditions
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7
Q

When is the pupil mydriatic?

A
  • in dim illumination
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8
Q

What’s the average diameter of a iris?

A
  • 12mm
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9
Q

Where is the iris thickest?

A
  • the collarette
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10
Q

Where is the iris collarette located?

A
  • 1.5mm from the pupillary margin
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11
Q

What does the collarette divide the iris into?

A
  • divides iris into pupillary zone and the ciliary zone
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12
Q

where is the pupillary zone located?

A
  • encircles the pupil
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13
Q

Where is the ciliary zone located?

A
  • extends from collarette to iris root
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14
Q

What’s the thickness of the iris root?

A

0.5mm

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15
Q

What’s the thinnest part of the iris?

A
  • iris root
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16
Q

What does the iris root join the iris to?

A
  • anterior part of the ciliary body
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17
Q

What are the four layers of the iris?

A

1) anterior border layer
2) stroma and sphincter muscle
3) anterior epithelium and dilator muscle
4) posterior epithelium

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18
Q

What is the anterior border layer a condensation of?

A
  • the stroma
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19
Q

What is the anterior border layer composed of?

A
  • fibroblasts and pigmented melanocytes
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20
Q

How are the fibroblasts and melanocytes arranged in the anterior border layer?

A
  • the highly branching processes of the cells interweave to form a meshwork
  • fibroblasts on the surface, melanocytes underneath
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21
Q

How might the melanocyte layer vary?

A
  • thickness varies with groups of melanocytes forming freckle like masses
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22
Q

Where is the anterior border layer absent?

A
  • iris crypts
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23
Q

What shape are iris crypts?

A
  • oval
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24
Q

What is the connective tissue stroma composed of?

A
  • pigmented and no pigmented cells
  • collagen fibrils
  • extensive ground substance
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25
Q

What are the pigmented cells of the tissue stroma?

A
  • melanocytes
  • clump cells
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26
Q

What are the non pigmented cells of the tissue stroma?

A
  • fibroblasts
  • lymphocytes
  • macrophages
  • mast cells
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27
Q

What’s the structure of a clump cell?

A
  • large
  • round
  • darkly pigmented
  • altered macrophages
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28
Q

Where are clump cells usually located?

A
  • pupillary portion of the stroma often near sphincter
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29
Q

How are the iris arteries structured?

A
  • branches of circular vessels
  • the major circle of the iris
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30
Q

Where is the major circle of the iris located?

A
  • located in the ciliary body near iris root
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31
Q

What encircles the iris vessels?

A
  • collagen fibrils from the stroma
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32
Q

What do the collagen fibrils that surround the iris vessels do?

A
  • anchor the vessels in place
  • protects them from kinking and compression during iris movement during miosis and mydriasis
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33
Q

What is the iris stroma continuous with?

A
  • stroma of the ciliary body
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34
Q

Where is the sphincter muscle located?

A
  • pupillary zone of the iris stroma
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35
Q

What is sphincter muscle composed of?

A
  • smooth muscle cells joined by tight junctions
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36
Q

What’s the shape and width of the sphincter muscle

A
  • circular
  • 0.75 to 1mm wide
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37
Q

What does contraction of the sphincter muscle cause?

A
  • causes pupil to constrict in miosis
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38
Q

What is posterior to the iris stroma?

A
  • anterior iris epithelium
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39
Q

What is the anterior iris epithelium composed of?

A
  • myoepithelial cells
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40
Q

What is the apical portion of the anterior iris epithelium composed of?

A
  • pigmented cuboidal epithelium joined by tight junctions and desmosomes
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41
Q

What is the basal portion of the anterior iris epithelium composed of?

A
  • elongated, contractile, smooth muscle processes
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42
Q

Where do the muscle fibers of the basal portion of the anterior iris epithelium extend to?

A
  • extend into stroma to form three to five layers of dilator muscle fibers joined by tight junctions
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43
Q

Where is the dilator muscle present from?

A
  • from the iris root to point in stroma below midpoint of sphinctor
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44
Q

How are the dilator muscle fibers arranged?

A
  • radically
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45
Q

What does the radial arrangement of the dilator muscles result in?

A
  • contraction of the dilator muscle pulls the pupillary portion towards the root, enlarging the pupil in mydriasis
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46
Q

What does the anterior iris epithelium continue to the pupillary margin as?

A

cuboidal epithelial cells

47
Q

What does the anterior iris epithelium continue posteriorly as?

A
  • the pigmented epithelium of the ciliary body
48
Q

What is the second layer posterior to the stroma?

A
  • posterior iris epithelium
49
Q

What’s the structure of the posterior iris epithelium?

A
  • single layer of heavily pigmented columnar cells
50
Q

How are the posterior iris epithelium cells joined?

A
  • tight junctions and desmosomes
51
Q

How does the posterior iris epithelium change at its periphery?

A
  • begins to lose its pigment as continues to ciliary body as non pigmented epithelium
52
Q

What covers the basal part of the posterior epithelium layer?

A
  • a thin basement membrane that lines the posterior chamber
53
Q

How are the anterior and posterior iris epithelial layers positioned?

A
  • apex to apex
54
Q

What forms the pupillary ruff?

A
  • epithelial cells curl around from posterior iris to anterior surface at pupillary margin
55
Q

What are crypts?

A
  • depressions or openings in the surface of the anterior eye surface
56
Q

Where are crypts located?

A
  • both sides of the collarette(Fuchs crypts)
  • near the root(peripheral crypts)
57
Q

What do crypts allow for?

A
  • allow the aqueous quick exit and entrance into spaces in the iris stroma as the volume of the iris changes during contraction and dilation
58
Q

What causes circular contraction folds?

A
  • result from tissue moving toward the iris root during pupillary dilation
59
Q

Where circular contraction folds found?

A
  • anterior surface of the ciliary zone
60
Q

what does the anterior iris surface appear like?

A
  • thin, radial, collagenous columns or trabeculae evident in lightly pigmented irises
61
Q

What are the small circular furrows near the pupil on the posterior iris surface?

A
  • Radial contraction furrows(of Schwalbe)
  • structural furrows of(of Schwalbe)
62
Q

What is iris colour determined by?

A
  • number of melanin granules within the melanocytes and the area they occupy
  • type of melanin present
  • arrangement of the connective tissue components
63
Q

Why can an iris appear blue?

A
  • the wavelength seen results from light scatter caused by the arrangement and density of the connective tissue components
64
Q

How’s the ciliary body look when viewed from front of eye?

A
  • ring shaped structure
65
Q

ciliary body width?

A
  • 5.9mm nasal
  • 6.7mm temporal
66
Q

How does the anterior and posterior ciliary body differ?

A
  • posterior ciliary body is fairly flat
  • anterior contains numerous folds or processes that extend into posterior chamber
67
Q

What are the two parts the ciliary body is divided into?

A
  • pars plicata
  • pars plana
68
Q

Pars plicata structure?

A
  • wider anterior potion of ciliary
  • contains ciliary processes
  • 70 to 80 ciliary processes extend into posterior chamber
  • regions between ciliary processes called valleys of kuhnt
69
Q

Pars plana structure?

A
  • flatter region of ciliary body
  • extends from posterior of pars plicata to the ora serrata
70
Q

ora serrata structure?

A
  • transition between ciliary body and choroid
  • serrated pattern
  • has forward pointing apices called dentate processes
  • rounded portions between processes called oral bays
  • dentate processes are elongations of retinal tissue
71
Q

structure of attachment of the zonule fibers and the lens?

A
  • course from the ciliary body to the lens
  • some fibers insert into internal limiting membrane of the pars plana region and travel through the valleys between the ciliary processes
  • some attach to the internal limiting membrane of the valleys of the plars plitata
72
Q

What is ciliary body attached to?

A
  • the vitreous base
73
Q

What is the outermost layer of the ciliary body?

A
  • supraciliaris
74
Q

What is the arrangement of the supraciliaris?

A
  • loose connective tissue arranged in ribbonlike layers containing pigmented melanocytes, fibroblasts and collagen bands
75
Q

What does the arrangement of the supraciliaris allow for?

A
  • arrangement of bands allows for ciliary body to slide agains sclera without detaching or scratching tissue
  • allows for accumulation of fluid within its spaces, which can lead to displacement from the sclera
76
Q

ciliary muscle structure

A
  • composed of smooth muscle fibers oriented in longitudinal, radial and circular directions
  • fibers bundle interweaving from layer to layer
  • various connective tissue found amongst muscle bundles
77
Q

longitudinal muscle fibers(of Brucke) location?

A
  • lie adjacent to supraciliaris and parralel to sclera
78
Q

longitudinal muscle fibers(of Brucke) structure?

A
  • each muscle resembles a long narrow V, base at scleral spur and apex in choroid
  • tendon of origin attaches muscle fibers to sclera spur and trabecular meshwork sheets
79
Q

Where are the radial muscle fibers located?

A
  • inner to the longitudinal fibers
80
Q

radial fibers structure?

A
  • wider shorter interdigitating V’s
  • originate at scleral spur
  • insert into connective tissue near the base of the ciliary processes
  • layer is a transition from the longitudinal oriented fibers to the circular fibers
81
Q

What makes up the innermost region of the ciliary muscle?

A
  • (Mullers) annular muscle
82
Q

(Mullers) annular muscle structure

A
  • circular muscle bundles
  • sphincter type action
  • located near major circles of the iris
83
Q

ciliarly muscle innervation

A
  • dually innervated by the autonomic nervous system
  • parasympathetic stimulation activates the muscle contraction
  • sympathetic innervation likely has inhibitory effect that is a function of the level of parasympathetic activity
84
Q

ciliary stroma location?

A
  • lies between the muscle and epithelial layers
  • forms core of each ciliary process
  • continuous with connective tissue that separates the bundles of the ciliary muscle
  • anteriorly is continuous with iris stroma
  • thins in pars plana, where is continuous with choroidal stroma
85
Q

What vessels are located within the ciliary stroma?

A
  • the major arterial circle of the iris
86
Q

major arterial circle of iris structure?

A
  • circular artery
  • formed by anastomosis of the long posterior ciliary arteries and the anterior ciliary arteries
  • stromal capillaries are large and fenestrated is the ciliary processes
87
Q

ciliary epithelium structure?

A
  • two layers of epithelium
  • positioned apex to apex
  • cover the ciliary body, posterior chamber and parts of the vitreous chamber
88
Q

What connects the two ciliary epithelial layers?

A
  • intercellular junctions
  • desmosomes
  • tight junctions
89
Q

What’s the function of the ciliary epithelium gap junctions?

A
  • allow for cellular communication between the layers
  • formation of aqueous
90
Q

Why are the two ciliary epithelial layers positioned apex to apex?

A
  • because of the invagination of the neural ectoderm in forming the optic cup
91
Q

ciliary epithelium outer layer structure?

A
  • pigmented and cuboidal
92
Q

what joins the ciliary epithelium outer layer cells?

A
  • desmosomes
  • gap junctions
93
Q

anteriorly what is the pigmented ciliary epithelium continuous with?

A
  • anterior iris epithelium
94
Q

posteriorly what is the pigmented ciliary epithelium continuous with?

A
  • retinal pigmented epithelium
95
Q

what attaches pigmented ciliary epithelium to the stroma?

A
  • basement membrane
96
Q

What is the ciliary basement epithelium continuous with?

A
  • anteriorly with basement membrane of the anterior iris epithelium
  • posteriorly with inner basement membrane portion of Bruchs membrane of choroid
97
Q

inner epithelial layer structure

A
  • non pigmented
  • columnar cells in pars plana
  • cuboidal cells in pars plicata
  • lateral walls contain extensive interdigitations
98
Q

What is inner epithelial layer joined by?

A
  • joined near apices
  • desmosomes
  • gap junctions
  • zonula occludens
99
Q

What is the nonpigmented ciliary epithelium continuous with?

A
  • anteriorly with posterior iris epithelium
  • posteriorly at ora serrata, becoming neural retina
100
Q

nonpigmented epithelial cells function

A
  • metabolically active
  • active secretion of aqueous humor
  • diffusion barrier between blood and aqueous
101
Q

Why do the ciliary non pigmented cells have more mitochondria than the pigmented ones?

A
  • higher metabolic activity
102
Q

what provides an extensive surface area to the posterior chamber?

A
  • basal and basolateral aspects of nonpigmented cells have numerous invaginations
103
Q

Where does the choroid extend from?

A
  • ora serrata to optic nerve
104
Q

Where is choroid located?

A
  • between sclera and retina
105
Q

choroid structure and function

A
  • primarily blood vessels
  • a thin connective tissue layer lies on each side of the stromal vessel layer
106
Q

Suprachoroid lamina structure

A
  • thin
  • pigmented
  • ribbonlike branching band of connective tissue
  • potential space between sclera and choroid vessels
  • contains features from both sclera and choroidal stroma
107
Q

What does the looseness of the suprachoroid lamina benefit it?

A
  • allows the vascular net to swell without causing detachment
108
Q

What does the suprachoroid lamina carry?

A
  • long posterior ciliary arteries
  • nerves from posterior to anterior globe
109
Q

Choroidal stroma structure

A
  • pigmented
  • vascularized
  • loose connective tissue layer
110
Q

What does the choroidal stroma contain?

A
  • melanocytes
  • fibroblasts
  • macrophages
  • lymphocytes
  • mast cells
111
Q

Choroidal stroma vessel structure

A
  • collagen fibrils arranged circularly around vessels
  • branches of short posterior ciliary arteries
  • vessels with larger lumina on outer layer
  • medium vessels pass inwards layer
  • medium vessels branch to form capillary bed
  • the venules join to become veins that gather in vortex pattern in each quadrant of the eye and exit choroid as four large vortex veins
  • contain no valves
112
Q

Choroidal vessel innervation

A
  • innervated by autonomic nervous system
  • sympathetic stimulation causes vasoconstriction and decreased choroidal blood flow
  • parasympathetic stimunlation causes nitrous oxide responsive vasodilation, resulting in increased choroidal blood flow
113
Q

Whats the choriocapillaris?

A
  • specialized capillary bed

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