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.
