Flashcards in Choroid Deck (24):
What does the choroid supply?
nourishment to the outer retina
is the choroid vascular or avascular?
the choroid is separated from the RPE by what?
What kind of tissue makes up the choroid?
connective tissue (vascular)
Can the choroid absorb light?
YES due to high pigmentation.
How thick is the choroid posteriorly? anteriorly?
(overall thin tissue)
What are the six layers of the choroid?
bruchs membrane (considered part of inner layers of choroid)
Sattlers (medium sized BV)
Hallers (big BV)
Lamina Fusca (most outer)
How big is the suprachoroid layer (including lamina fusca)? What types of cells are located here? is the suprachoroidal space vascular or avascular?
melanocytes, fibroblasts and connective tissue fibres.
Stroma of the choroid is made up of which layers? vacular or avascular? What cells are located here? How does this layer differ in darker people compared to lighter skinned people?
sattlers and hallers
collagen one, fibroblasts, collagen fibres and melanocytes also has mast cells, macrophages and lymphocytes.
it will be darker pigmented in darker people.
The vascular layers of the choroid are supplied from? how do they drain?
short posterior ciliary arteries (supply posterior choroid)
vortex veins (4-6, each vein drains one section of choroid) which further drain into sup/inf opthalamic veins after piercing sclera.
what do the long posterior ciliary arteries supply? central retinal artery?
anterior part of choroid.
supplies the major circle of iris.
where is the density of choriocapillaris layer greatest? it extends to what structure? how are the capillaries fed?
at the fovea.
from feeder arterioles in sattlers layer (one feeder supplies one hexagonal patch of capillaries).
venules all come together to form what?
larger veins (vortex veins)
What are some main functions of the choroid besides blood supply to outer retina?
thermoregulation by blood flow
blood flow regulation can affect IOP
possible role in eye growth regulation?
possible role of another means of accommodation? (i.e. large changes in thickness in response to defocus in animals, changes are smaller in humans but still present).
In chickens it has been found that the choroid does what in response to myopic defocus? hyperopic lens? difference between chickens and humans?
thicken (therefore if positive lens held to eye, choroid will thicken)
thin (if a negative lens held to eye, choroid will thin)
in chickens this happens within seconds, for humans it can take hrs.
The choroid is highly pigmented due to what? high pigmentation is characteristic of what type of animals?
microvilli at the RPE intercalate with?
O2/nutrients pass through what to get to the RPE?
What type of cells are present in lamina fusca?
melanocytes therefore pigmented.
photoreceptors are part of inner or outer retina?
How many SPCA? How many LPCA?
10-20 (they pierce sclera in a ring around optic nerve)
2 of these, pierce sclera further anteriorly.
How many anterior ciliary arteries? what do they travel along? to form what?
seven of these they go with EOMs and form major circle of iris.
Since the choroid sits in front of the sclera, what can it do?
protect the sclera from increases in IOP.