Uveal Tract Flashcards
page 140-158
Where does the choroid lie?
Between sclera and RPE. Extends from optic nerve to ciliary body.
Where is the chord thickest and where is it thinnest (include measurements)?
Thickest at posterior pole (022.mm)
Thins gradually anteriorly to 0.1mm
Describe inner vs outer surfaces of choroid?
Inner surface = smooth (firmly attached to RPE), outer surface = rough
Where is choroid adherent to sclera?
Site of exit of vortex veins and optic nerve head
What happens to choroid at optic nerve head?
Becomes continuous with Pia and arachnoid
Name the space found between sclera and choroid
perichoroidal space
What runs across and within perichoroidal space?
Across = thin, pigmented connective tissue - suprachoroid lamina
Within = long and short posterior ciliary arteries and nerves
Name the two layers of the choroid
1) vascular layer
2) Bruch’s membrane
VASCULAR LAYER CHOROID
Name three layers from inner to outer
Choriocapillaris (capillary layer)
Sattler’s layer (medium vessel layer)
Haller’s layer (Large vessel layer)
CAPILLARY LAYER CHOROID
What size and type of vessel?
What are these vessels supported by?
Sattler and Haller’s layers choroid:
a) What type of tissue found here
b) What kind of cells beside those forming blood vessel
c) size of blood vessels
d) where do they branch from and extend to
e) how do they compare to arteries found elsewhere in body
f) size of veins compared to arteries, what do they join to form?
VESSEL LAYER CHOROID
a) loose connective tisse
b) Melanocytes
c) large-medium sized blood vessels
d) Branches of short posterior ciliary arteries - extend anteriorly
e) both contain internal elastic lamina + smooth muscle media
f) veins = larger, join to form 4-5 vortex veins that pierce sclera to join ophthalmic veins
CHORIOCAPILLARIS
a) inner or outer layer?
b) diameter of capillaries
c) Features of vessel walls
d) supporting cell name and role
e) where is density highest and lumen widest?
f) What is supply and where do they drain to?
a) inner
b) 40-60microns
c) thin wall, fenestrated
d) pericytes
e) macula
f) arteries from vessel layer (Sattler’s and Haller’s), drain to veins in vessel layer
BRUCH’s MEMBRANE
a) how many layers
b) name the layers
a) five
b)
1) BM of endothelium of capillaries in choriocapillaris
2) outer layer of collagen
3) meshwork elastic fibres
4) inner layer collagen fibres
5) BM RPE
BRUCH’s MEMBRANE CONT
a) how thick is Bruch’s membrane?
b) what is it’s function?
a) 2-4microns
b) unknown ?fluid transport from choroid to retina
Nerve supply of choroid
- what other fibres do they carry?
long and short ciliary nerves
- long carry sensory and sympathetic
- short carry sympathetic and parasympathetic
pierce sclera around optic nerve, travel anteriorly through supra choroidal space
What are the long ciliary nerves branches of?
nasociliary nerve, branch of ophthalmic division of trigeminal nerve
Where do the short ciliary nerves arise from?
ciliary ganglion
What is the function of the choroid?
- nourish outer layers of retina
- conduct blood vessels forward to anterior portion of eye
- heat exchange from retina
- may assist in regulating IOP
- absorb light penetrating retina, preventing reflection
CILIARY BODY
what are the functions of the ciliary body?
- aqueous formation
- lens accommodation
- aqueous drainage via uveoscleral outflow and trabecular system
CILIARY BODY
gross structure of ciliary body
- shape + cross section
- width
- continuous with what structure anteriorly and posteriorly
- extends forwards and backwards to which structures
Doughnut-shaped, triangular in cross section (base faces AC, anterior outer angle faces scleral spur. Apex extends posteriorly and laterally to become continuous with choroid. Anterior surface = ridged and is called pars plicata)
6-7mm wide (temporal > nasal)
Anteriorly continuous with peripheral margin iris
posteriorly continuous with choroid
extends forwards to scleral spur and backwards to ora serrata
CILIARY BODY - origin and insertion points
originates how far posterior to limbus
how far posterior to this does it extend on temporal vs nasal side
starts 1.5mm posterior to limbus
temporally: extends a further 7.5-8mm posteriorly to this point
nasally: a further 6.5-7mm posterior to this point
(ie wider temporally than nasally)
CILIARY BODY
which two parts can the ciliary body be split into
pars plana and pars plicata
Plana - anterior surface
plicata - posterior surface
CILIARY BODY
In which part of the ciliary body are the ciliary processes found?
Pars plicata
CILIARY BODY
Where do the lens zones attach?
Attach to the pars plicata at intervals between the ciliary processes
CILIARY BODY
Where is the equator of the lens in relation to the ciliary processes?
0.5mm away
CILIARY BODY
Describe the appearance of the posterior margin of the pars plana, which structure is adjacent to this?
scalloped edge, fits into and corresponds with ora serrate of neural retina
The layer of choroid comprising large arteries and veins is which of the following:
Bruch’s membrane
Haller’s layer
Sattler’s layer
the choriocapillaris
Haller’s layer lies within the choroid and comprises large arteries and veins. Sattler’s layer, which lies above Haller’s layer, is composed of arterioles and venules which supply the choriocapillaris directly above.
Why is the pars plana surgically an important anatomic structure?
The pars plana is surgically an important anatomic structure. Because of its relative avascularity and position anterior to the retina, incisions through the sclera and choroid into the vitreous should be made at this point to avoid hemorrhagic complications and retinal detachments.
Why may a lesion in the choroid result in retinal atrophy?
Because the uveal tract provides nourishment for the outer part of the retina, a lesion of the choroid may interfere with nutrition to the adjacent retina and cause atrophy and destruction of the retina.
CILIARY BODY
Which three structures is the ciliary body made of? Which one forms the bulk of it?
Ciliary epithelium
Ciliary stroma
Ciliary muscles
Ciliary muscles
CILIARY EPITHELIUM
a) How many layers
b) which type of cell
c) what does it correspond to embryologically
d) describe appearance of inner layer, what is it continuous with, do they line any other area of the eye?
e) Describe the appearance of the outer layer, what is it continuous with? What does it sit on?
f) describe orientation of cells of inner and outer epithelial layers relative to each other?
g) are these layers in contact with each other?
a) 2
b) cubical
c) two layers of optic cup
d) non-pigmented, continuous with nervous part of retina. Also lines AC
e) pigmented, continuous with RPE, sits on ciliary stroma (ie it is OUTER LAYER :p)
f) base of inner layer faces into eye, base of outer layer faces towards stroma of epithelium => cells sit apex-to-apex
g) at points separated by small ciliary channels
CILIARY EPITHELIUM
a) What is the basement membrane of the non-pigmented layer continuous with?
b) what is the basement membrane of the pigmented cells continuous with?
a) inner limiting membrane of retina
b) basememnt membrane of pigmented epithelium of retina
CILIARY EPITHELIUM - non-pigmented layer
Describe structure of non-pigmented cells
(plasma membrane structure + which organelles highest in number)
basal and lateral plasma membranes have extensive folds which interdigitate with neighbouring cells
well developed Golgi apparatus, lots of granular and granular endoplasmic reticulum, lots of mitochondria
Appearance = similar to that of cells involved in active transport of water + ions + secretions
CILIARY EPITHELIUM - pigmented layer
Describe which organelles present and how abundant they are
Describe structure of plasma membranes
LOTS of melanosomes
Scanty, small Golgi apparatus
fair amount of mitochondria
basal plasma membrane - infolding because involved ion transport
What is thought to be the role of ciliary epithelium
Both layers thought to have involvement in production of aqueous humor
Lots of cell attachment between layers means they are likely coordinated with each other
CILIARY STROMA
Describe structure
Does it contain any other structures
Where does connective tissue extend to
bundles of loose connective tissue, rich in blood vessels and melanocytes
Contains embedded ciliary muscles
Connective tissue extends to ciliary processes to form connective tissue core
CILIARY STROMA
a) Which blood vessels found in stroma?
b) What is found at the peripheral edge of the iris? What is it formed by?
c) describe the structure of the endothelium of the capillaries close to the ciliary epithelium
a) ciliary arteries, veins and capillary networks
b) Major arterial arcade - formed by branches of long posterior ciliary arteries
c) fenestrated
CILIARY MUSCLE
a) where do most of the muscles attach?
b) which three groups of fibres can the muscle be split into?
c) which type of muscle are they?
a) scleral spur
b) Longitudinal/meridional fibres, oblique/radial fibres, circular fibres
c) smooth muscle
CILIARY MUSCLE
a) where are the longitudinal/meridional fibres found?
b) where are the oblique/radial fibres found?
c) where are the circular fibres?
a) most external, closest to sclera - pass posteriorly into stroma of choroid
b) run from first to third layer of muscles and radiate out from scleral spur
c) most internal, run around eye like sphincter. Lie close to peripheral edge of lens
CILIARY MUSCLE
a) what role does contraction of the ciliary muscle play?
Contraction of the ciliary muscle (especially longitudinal and ciruclar fibres) pulls ciliary body forward in accommodation.
Forwards movement –> less tension on suspensory ligament => elastic lens becomes more convex and refractive power increases
CILIARY MUSCLE
What is the innervation of the ciliary muscle?
postganglionic parasympathetic fibres derived from oculomotor nerve
Reach muscle via ciliary nerve
IRIS
Name the two margins of the pupil. What does the peripheral one attached to
Ciliary margin (peripheral) attached to anterior surface of ciliary body aka root of iris
Pupillary margin
IRIS
What is the textbook description of the iris?
“thin, contractile, pigmentary diaphragm with central aperture. Suspended in AQ between cornea and lens. Divides space between lens and cornea into posterior and anterior chamber”
IRIS
a) diameter
b) where is it thickest (+ how thick)
c) where is it thinnest
IRIS
a) 21mm
b) pupillary margin 2mm
c) ciliary margin
IRIS
a) size of pupil
b) what percentage of the population have physiologic anisocoria
c) what is responsible for the colour of the iris
d) why do albino people have reddish irises?
a) 1mm-8mm
b) 25%
c) presence of pigment in melanocytes. Blue eyes don’t have much pigment => longer wavelengths absorbed, shorter wavelengths (blue) reflected.
d) melanocytes contain NO melanin => Hb in blood vessels of iris and retina give reddish colour
IRIS
describe the flow of aqueous humor
formed in ciliary processes in posterior chamber, circulates through pupil to anterior chamber and exits into sinus venous sclerae at iris-corneal angle
ANTERIOR SURFACE OF IRIS
a) what is the iris divided into?
b) which structure divides it?
c) where is this structure found?
d) describe the anterior surface of the iris
e) what produces the ridges in the ciliary region of the pupil
f) where do the branches of the major arterial circle anastomose? what do they form here?
g) where are the contraction furrows found and what is their purpose
h) what are the iris ruffs?
a) pupillary zone and ciliary sone
b) collarette (circular, wavy ridge)
c) 2mm from pupillary margin (NB - iris is thickest here)
d) No epithelium. Radial streaks formed by trabeculae/bands of connective tissue. These enclose Fuch’s crypts (oval shaped crypts that communicate with tissue space of iris)
e) underlying bloods vessels (branches of major arterial circle)
f) at the collarette
g) near outer part of colliery region, fold as pupil dilates
h) radial folds of pigmented posterior epithelium seen at pupillary margin where the epithelium wraps over edge of pupil for short distance
IRIS
What is ectropion urea and what can it indicate?
when pigmented epithelium of it is extends around pupil margin more extensively than normal.
Indicates possible tumour/other serious pathology causing abnormal traction on iris
POSTERIOR IRIS
what colour is the posterior surface of the iris?
Describe the shape its folds
black
lots of radial contraction folds, come circular folds at periphery
IRIS
Name the two layers of the iris
Where are they derived from embryologically
Stroma (anterior) - from mesenchyme
TWO epithelial layers (posterior) - from neural ectoderm
STROMA OF IRIS
a) describe the structure of the stroma of the iris (name 8 things it contains)
connective tissue, highly vascular. Contains:
- collagen fibres
- fibroblasts
- melanocytes
- matrix
- nerve fibres
- smooth muscle of sphincter pupillae
- myoepithelial cells of dilator papillae
STROMA OF IRIS
ANTERIOR SURFACE OF STROMA
a) does it contain epithelium?
b) what three things does it contain?
c) Fuch’s crypts allow communication between the stroma and….?
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) NO
b) fibroblasts, melanocytes, collagen fibres
c) anterior chamber
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) what is the diameter of the collagen fibrils found here?
b) what is the distance between the collagen fibrils?
c) how are they arranged?
d)what is found in between collagen fibrils on the anterior surface of the iris?
e) are there any elastic fibres here?
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) 60nm
b) 50-60nm
c) loosely
d) fluid rich in mucopolysaccharides
e) NO
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) describe the shape of the fibroblasts found here
b) what happens to the fibroblasts at the irido-corneal angle
c) describe the shape of the melanocytes
d) do all melanocytes found here contain the same amount of melanosomes
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) have numerous branching processes
b) blend in with the fibroblasts found in the TM
c) also have numerous branching dendritic procrsses
d) Nope
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) where is the sphincter pupillae muscle found?
b) What kind of muscle is it?
c) how wide is it?
d) what separates the bundle of muscle and what does it contain?
e) how many muscle cells are connected in each bundle of muscle? What connects them?
f) Where do the nerve fibres typically end?
g) what happens when the sphincter pupillae contracts?
h) what is its nerve supply?
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) pupillary zone - ring around the pupil
b) smooth muscle
c) 1mm
d) connective tissue containing blood vessels, motor and sensory nerves
e) 6-8 cells connected by GAP JUNCTIONS
f) on one cell at the periphery of each muscle group
g) pupil constricts :p
h) parasympathetic postganglionic fibres of the short ciliary nerves. Derived from oculomotor nerve.
What are gap junctions?
channels that connect the cytoplasm of adjacent cells, allowing the exchange of ions, small molecules, and second messengers.
What are tight junctions?
Multi-protein complexes that act as cell-cell adhesion structures in epithelial and endothelial tissues:
Regulate the movement of water, nutrients, and ions across cells, and maintain cell polarity. They also create a barrier that separates the apical and basolateral plasma membrane domains.
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) where is the dilator pupillae found?
b) What type of muscle is it?
c) where is it derived from?
d) what shape is the muscle process of this cell? how long and thick are they?
e) where do the nerve fibres supplying the dilator pupillae terminate? Are they myelinated?
f) What happens to the pupil when the dilator pupillae contracts?
g) What is the nerve supply to the dilator pupillae?
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
a) from iris root to sphincter pupillae
b) myoepithelium
c) anterior layer of the iris pigment epithelium that covers the posterior surface of the iris.
NB: whole cell contains myofilaments, but they are more concentrated in the muscular process
d) spindle shaped, 60 microns long and 4 microns thick
e) close to the plasma membrane. NON-myelinated
f) pupil dilates/enlarges :p
g) sympathetic post-ganglionic fibres via long ciliary nerves
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
Where are they sphincter pupillae and dilator pupillae derived from embryologically?
STROMA OF IRIS
ANTERIOR SURFACE OF IRIS
- external layer of optic cup
NB: sphincter acts in bright light and accommodation reflex
dilator acts in dim light + heightened sympathetic activity (eg fear)
STROMA OF IRIS
TWO POSTERIOR EPITHELIAL LAYERS OF IRIS
a) where are the two posterior epithelial layers of the iris derived from embryologically?
b) how are the layers apposed to one another?
c) what is found between these two layers?
d) what happens if this is filled?
STROMA OF IRIS
TWO POSTERIOR EPITHELIAL LAYERS OF IRIS
a) neuroectoderm of two layers of optic vesicle
b) apex to apex
c) potential space
d) iris cyst forms
STROMA OF IRIS
TWO POSTERIOR EPITHELIAL LAYERS OF IRIS
a) what is the anterior epithelial layer in contact with?
b) do the cells of the anterior epithelium contain melanin?
c) what is the anterior layer continuous with?
d) what is the posterior layer in contact with?
e) which are bigger - cells in anterior or posterior layer?
f) do cells of posterior layer contain melanin?
g) what is the posterior layer continuous with?
STROMA OF IRIS
TWO POSTERIOR EPITHELIAL LAYERS OF IRIS
a) stroma of iris
b) a few
c) outer pigmented layer of ciliary epithelium
d) aqueous humor
e) posterior layer (cuboidal)
f) yes
g) inner non-pigmented layer of ciliary epithelium
STROMA OF IRIS
TWO POSTERIOR EPITHELIAL LAYERS OF IRIS
a) describe the shape of the apical plasma membrane of the epithelial layers
b) what connects the later plasma membranes of adjacent cells of the two posterior epithelial layers together?
STROMA OF IRIS
TWO POSTERIOR EPITHELIAL LAYERS OF IRIS
a) microvilli that project into small intercellular spaces
b) tight junctions and desmosomes
BLOOD SUPPLY OF IRIS
a) what is the blood supply of the iris?
b) how many vessels supply this?
c) what kind of pattern do the arteries of the iris form? What does this allow for?
d) what vascular structure is found at the collarette?
BLOOD SUPPLY OF IRIS
a) radial vessels in the iris stroma derived from major arterial arcade found in ciliary body
b) Two long posterior ciliary arteries and seven anterior ciliary arteries
c) spiral pattern (seen as radial ridges on anterior surface of iris) . Allows for movement of iris when it dilates/constricts
d) minor arterial circle of the iris
BLOOD SUPPLY OF IRIS
a) describe the venous drainage of the iris
b) what do they drain into
BLOOD SUPPLY OF IRIS
a) follow arteries in forming minor venous circle
DOES NOT DRAIN INTO MAJOR VENOUS CIRCLE, rather drain into vortex veins
BLOOD SUPPLY OF IRIS
a) are the blood vessels of the iris fenestrated or non fenestrated?
b) are there tight junctions between the endothelial cells lining the vessels of the iris?
c) what happens when the iris is inflamed as a result of this?
SEE PAGE 154 FOR MORE INFORMATION ON VESSELS
Blood supply of iris
a) non-fenestrated
b) nope
c) vessels become leaky - cells and proteins/other large molecules leak into AC.
NERVE SUPPLY OF IRIS
a) where does the iris get its sensory and autonomic nerve supply from?
b) what are the long ciliary nerves branches of?
c) where do they get their sympathetic fibres from?
d) where do they get their sensory fibres from?
e) which structures of the long ciliary nerves innervate in the iris?
NERVE SUPPLY OF IRIS
a) long and short ciliary nerves
b) branches of nasociliary branch of ophthalmic division of trigeminal nerve
c) superior cervical sympathetic ganglion
d) trigeminal nerve
e) dilator pupillae and blood vessels
NERVE SUPPLY OF IRIS
a) where do the short ciliary nerves arise from?
b) what other nerve fibres do they carry (+where from)?
c) Where does the parasympathetic pathway originate?
d) Which structures are innervated by the short ciliary nerves?
NERVE SUPPLY OF IRIS
a) ciliary ganglion
b) post-ganglionic parasympathetic nerve fibres + a few sympathetic fibres
c) Edinger Westphal nucleus of oculomotor nerve
d) sphincter pupillae
a) what proportion of the light entering the eye is controlled by the iris ( + in log units)
1/10th (one log unit)
What happens to the choroid with age? (3)
atrophy + depigmentation –> patchy appearance of red glow at periphery of Fundus
thickening of Bruch’s membrane, ‘drusen’
blood vessel sclerosis after age of 60
What is the most common intraocular tumour and where is it derived from?
malignant melanoma
melaonocyte of choroid/ciliary body/iris
What is pupillary block glaucoma?
When entire pupillary becomes stuck to lens secondary to inflammation (think synechiae but extreme)
What percentage of the total ocular blood flow passes through the uveal layer?
98%
85% - choroid
7% - ciliary body
5% - iris
