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Neural Biology 1 > choroid > Flashcards

choroid Flashcards

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1
Q

what is the choroid?

A

the middle layer of eye in the posterior globe interior to it is the retina and external to it sclera

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2
Q

how does the thickness of the choroid vary?

A
  • thickness of choroid varies with location
    anteriorly near ora serrata = as little as 60um
    behind macular region = choroid is thick 160um
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3
Q

how thick is the choroid in a myopic eye ?

A

myopic eye - the eye is elongated so coat is stretched making the choroid thin

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4
Q

what are the three coats of the back of the eye?

A
  • sclera - made of irregular dense collagen fibres
  • choroid-
  • retina-
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5
Q

what separates the choroid and sclera?

A

suprachoroid- outer boundary of choroid

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6
Q

what separates the choroid from the retina?

A

Bruch’s membrane

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7
Q

what is between the suprachoroid and Bruch’s membrane?

A

3 layers of blood vessels

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8
Q

what are the layers of the choroid?

A
  1. suprachoroid
  2. stroma - Haller’s layer
    - Sattler’s layer
  3. choriocapillaris
  4. Bruch’s membrane
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9
Q

what is the choroid mainly made of ?

A

the choroid is mainly blood vessels

  • blood vessels near the sclera are very large
  • blood vessels near the retina are smaller
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10
Q

what are the three layers of vessels in the choroid?

A

Haller’s layer - large which divide into
Sattler’s - medium
choriocapillaris - smaller

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11
Q

what is suprachoroid

A
  • also known as lamina suprachoroidea or lamina fusca
  • composed of fine network of collagen fibres and between collagen fibres we have ciliary nerves running from front to back of eye which supply uveal tract
  • also find some melanin granules
  • a lot of nerves travel
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12
Q

what is the whole layer of blood vessels know as ?

A
  • choroidal stroma- which is split into Haller’s layer which is split into Sattler’s internal to that is choriocapillaris
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13
Q

what does choroidal vessels constitute of ?

A
  • choroidal vessels constitute a compressed hierarchy

- vessel branching occurs close together which produces a layered appearance

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14
Q

what does bruch’s membrane separate ?

A

RPE - retinal pigment epithelium from choriocapillaris

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15
Q

what is Bruch’s membrane made of ?

A

non-cellular connective tissue

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16
Q

what are the layer of Bruch’s membrane? from external to internal

A
  • basal lamina - secreted by choriocapillaris
  • collagen - provided by choriocapillaris
  • elastin
  • collagen- provided by RPE
  • basal lamina - secreted by RPE-
17
Q

what is the thickness of Bruch’s membrane?

A

2-6um

increases with age

18
Q

what does choriocapillaris supply?

A
  • choriocapillaris supplies nutrients to the outer five layers of the retina
19
Q

what happens if Bruch’s membrane become thicker?

A
  • the thickness of bruch’s membrane has some significance because if it gets thicker than the transport of nutrients from choriocapillaris into retina can become impaired
  • causing Drusen
20
Q

what is Drusen?

A

common pathology - accumulation of debris in bruch’s membrane

  • Drusen can push the retina away from Bruch’s membrane and away from choriocapillaris
  • can impair flow of nutriebts
21
Q

what happens if Bruch’s membrane breaks?

A
  • if it breaks you get local retinal edema - fluid gets through choriocapillaris and through the retina
22
Q

what is function of Bruch’s membrane?

A
  • limits fluid movements towards the retina under normal conditions
  • very important in retinal pathologies
23
Q

why is choriocapillaris important?

A
  • provide nutrients to the outer five layers of the retina
24
Q

where the 5 inner layers of retina recveive blood supply from ?

A
  • from the central retinal artery
25
Q

where do the 5 outer layers receive nutrients from ?

A
  • they are devoid of blood vessels and receive their nutrients from the choriocapillaris
26
Q

what are unique characteristics of choriocapillaris ?

A
  • large in diameter and fenestrated
  • fenestration 60-80 nm in diameter and covered by thin diaphragm
  • large fenestrations to allow the passage of substances such as vitamin A which is need to make visual pigments within the photoreceptors
  • fenestrations only occur on the retinal side of the capillary - the side facing Bruch’s membrane
27
Q

what is main function of chorioid

A

through choriocapillaris to supply nutrients to 5 outer layers of retina

28
Q

why is blood flow high in the choroid?

A
  • rate of blood in the choroid is very high - much higher than needed to supply the retina - may be due to thermoregulation function used to cool the outer retina during bright light exposure thus preventing damage
29
Q

what do we have between blood vessels in the choroid ?

A
  • connective tissue components such as collagen fibres , plasma cells , mast cells and macrophages
30
Q

what other thing can be found in the choroid?§

A
  • melanin granules in pigmented cells known as melanocytes
31
Q

what is the function of melanin in the choroid?

A

the melanin of the choroid along with that of ciliary body, iris and retina contributes to the eye’s black box effect( light that isn’t absorbed by photoreceptors) , serving to absorb stray light

32
Q

where does the eye’s blood supply come from ?

A

the eye’s blood supply comes from internal carotid artery, a branch off the aorta

33
Q

explain the eye’s blood supply?

A
  • when the left ventricle contracts it pushes the blood through the aorta
  • one of the first vessels that comes of the aorta is common carotid artery which takes blood up to head and neck
  • common carotid artery spilts into internal and external carotid
34
Q

what is the main vessel supplying the eye ?

A
  • the main vessel supplying the eye is the ophthalmic artery, a branch of the internal carotid
  • branches off the ophthalmic artery supply various ocular structures
  • the globe is supplied by anterior and posterior ciliary arteries
  • anterior ciliary arteries pierce the globe anteriorly near the limbus
  • posterior ciliary arteries pierce the sclera near the optic nerve head.
  • short posterior ciliary arteries supply the choroid
  • long posterior ciliary arteries
    and supply the iris
35
Q

which arteries supply the choroid?

A
  • short posterior ciliary arteries which come into back of eye supply the choroid
36
Q

which arteries supply the iris and ciliary body ?

A

long posterior ciliary arteries which come into the back of eye which run anteriorly and join anterior ciliary arteries and supply the iris and ciliary body

37
Q

where do anterior ciliary arteries and long posterior ciliary arteries join ?

A
  • anterior ciliary arteries and the long posterior arteries join together at the base of the iris at the major iridic circle
  • in the major iridic circle you have vessels that go into iris into ciliary body and some recurrent branches which supply the anterior choroid

Neural Biology 1 (58 decks)

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