Choroid

the choroid begins anteriorly at _____

the choroid ends posteriorly at _____

begins at ora serrata

ends at optic nerve head

the choroid sits between the ____ & _____

retina & sclera

t or f: the choroid is a highly vascularized tissue

TRUE

3 layers of choroid (label external/internal)

(external) suprachoroid, stroma, choriocapillaris (internal)

the suprachoriod is continuous with...

supraciliaris

what type of cell is found abundantly in the suprachoroid? what is its function?

melanocytes

create a dark chamber & reduce oxidative stress

is the suprachoroid located internally or externally? (compared to the other layers of the choroid)

externally

longitudinal fibers from the ciliary body insert into what layer of the choroid?

suprachoroid

which layer of the choroid is a potential space?

suprachoroid

the suprachoroid attaches the choroid to what layer?

scleral proper

function of the suprachoroid

allows for choroid remodelling without disrupting the retina or sclera

t or f: the suprachoroid is highly innervated

true

what type of tissue is the suprachoroid?

LCT

t or f: the direction of the collagen fibers in the suprachoroid is anterior-posterior

false, they run diagonally

what is the widest layer of the choroid?

stroma

components of the choroid stroma

connective tissue, collagen, fibroblasts, APCs, melanocytes, blood vessels

what are the layers of blood vessels in the stroma named?

haller's & sattler's

what is Haller's layer?

external layer of LARGE lumened blood vessel in choroid stroma

what is Sattler's layer?

internal layer of NARROW lumened blood vessels in choroid stroma

choroid stroma is directly continuous with...

ciliary body stroma

the blood vessels in Haller's & Sattler's are... (fenestrated/non-fenestrated)

non-fenetrated (not leaky)

what is the choriocapillaris?

single layer of fenestrated (leaky), anastamosing (joined) capillaries

what is the function of the choriocapillaris?

deliver nutrients (especially to retina)

what layer lies directly external to the choriocapillaris? what lies internal?

external - choroid stroma/Sattler's

internal - Bruch's membrane/RPE

t or f: the choroid capillaries in the choriocapillaris have a narrow lumen

false, they have a wide lumen

t or f: the choroid capillaries in the choriocapillaris have pericytes

true

what is the purpose of pericytes?

control movement of nutrients

the retina is supported by 2 blood supplies. what are they?

choroid & retinal vasculature

choroid vs. retinal vasculature: which is responsible for supporting the internal retina?

retinal vasculature

choroid vs. retinal vasculature: which is responsible for supporting the macula/fovea?

choroid vasculature

t or f: the high arteriole-to-venule ratio predisposes the choroid to hemorrhages

false, it has a predisposition to edema

high arteriole-to-venule ratio makes the tissue resistant to...

ischemia

where is the arteriole-to-venule ratio the highest?

macula & peripapillary area

where is the arteriole-to-venule ratio the lowest?

equatorial & periphery

t or f: the arteriole-to-venule ratio is inversely related to the number of photoreceptors in an area

false, they are directly proportional

increase ratio = increase number of photoreceptors

a low arteriole-to-venule ratio make a tissue suseptible to _____, but resistant to _____

suseptible to ischemia

resistant to edema

t or f: Haller's & Sattler's are only distinct in the periphery

false, they are distinct in the central region

which cell in the choriocapillaris controls the movement of nutrients?

pericytes

t or f: the absence of retinal vasculature in the fovea decreases light scatter

true

t or f: Bruch's membrane is a less efficient method of nutrient delivery, but it is used between the choroid/RPE to control the delivery of nutrients

false, Bruch's is more efficient

5 layers of Bruch's membrane

1. BM of the choriocapillaris

2. outer collagenous layer

3. elastic layer

4. inner collagenous layer

5. BM of the RPE

t or f: the BM of choriocapillaris is discontinuous

true

main type of collagen in the BM of the choriocapillaris

type IV

main type of collagen in the outer collagenous zone

type I

main type of collagen in the inner collagenous zone

type I

main type of collagen in the BM of the RPE

type IV

the outer & inner collagenous zones are held together by...

elastic layer

t or f: the outer collagenous zone is made during embryology

false, the inner collagenous is made during embryology

where does Bruch's membrane taper?

pars plana

as you approach the retina, the BM of the non-pigmented ciliary epithelium is continuous with...

the internal limiting membrane of the neural retina

as you approach the retina, the BM of the pigmented ciliary epithelium is continuous with...

the BM of the RPE (part of Bruch's)

t or f: Bruch's dead ends at the ora serrata

false, most of the components of Bruch's will end, but the RPE BM will be continuous with the pigmented ciliary epithelium BM

innervation of the choroid

sympathetic (directly stimulates vasocontriction)

parasympathetic (indirectly stimulates vasodilation)

functions of the choriod

absorb stray light

thermoregulation

remove waste

supply blood to retina

what is drusen?

degeneration of Bruch's membrane

collection of lipid & BM-like material in the inner collagenous zone

drusen increases your risk for developing...

age-related macular degeneration

what are the 2 types of AMD?

geographic atrophy/dry

wet

dry AMD is characterized by _____

wet AMD is characterized by ____

dry - RPE loss

wet - neovascularization

t or f: humans have a tapetum lucidum

false :(

which layer is the tapetum lucidum present in?

Sattler's layer

what is the purpose of the tapetum lucidum?

increase light scatter to improve light sensitivity/night vision