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Ocular Physiology #2 > Vitreous Humor > Flashcards

Flashcards in Vitreous Humor Deck (50)
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2

how much of the eye is vitreous humor

80% (largest structure)

3

how long is the vitreous chamber in newborns

10.5mm

4

how long is the vitreous chamber in adults

16.5mm

5

how much of the vitreous is water

about 98%

6

what are the non-aqueous biochemical components of the vitreous

collagen and glycosaminoglycans (GAGs) that form the vitreous into a viscoelastic gel

7

when does the vitreous gel become liquified

it decreases with age-starting the day we are born, 20% (volume) by age 18 and progresses to 50% by 80th decade

8

what are the 2 types of collagen in the vitreous

type 2 (75%) and combined type 5/11 (10%)

9

what are 2 difficulties that arise in attempting to investigate the vitreous

it is "invisible" tissue and previous techniques are combined with artifacts, it is hard to make interpretations on the true in vivo situation

10

how is the primary vitreous formed

the optic cup is maintained by the lens vesicle, as the cup grows it is filled by fibrillar material (secreted by cells of embryonic retina), then the hyaloid artery penetrates and more fibrillar material from blood vessel cells fills the space

11

when does the secondary vitreous form

at the end of the 6th week

12

what happens as the secondary vitreous is formed

the size of the vitreous cavity increases and the hyaloid vascular system regresses

13

what is present after the hyaloid artery regresses

a tube in the primary vitreous surrounded by the secondary vitreous- Cloquet's canal

14

where does cloquet's canal extend to and from

from the retrolental space to the optic nerve

15

what type of vitreous are the zonules

tertiary vitreous

16

what shape does the mature vitreous have

spherical except anteriorly which is concave shape for the lens

17

What does the vitreous base extend from

a 3-D zone extending from 2mm anterior to 3mm posterior to the ora serrata and it is several mm thick

18

what is the cortex

the outermost part of the vitreous; divided into anterior cortex and posterior cortex

19

where in the vitreous is collagen densely packed

in the base area

20

what is the vitreoretinal interface

the outer part of the vitreous cortex, including anchoring fibrils of the vitreous body and the internal limiting membrane of the retina

21

how thick is the internal limiting membrane on the retina

between 1 and 3 microns thick

22

where are the 4 places the vitreous cortex is firmly attached to the internal limiting membrane at

the vitreous base, around the optic disc (weiss ring), at the vessels and in the area surrounding the foveola

23

the INM (internal limiting membrane) is the basal lamina of which cells

the muller cells

24

what is the internal limiting membrane made of

mainly type 4 collagen and proteoglycans

25

what does the gel structure of the vitreous act as a barrier against

the movement of solutes

26

what are the two processes substances move by in the vitreous

diffusion or bulk flow

27

why does bulk flow occur in the vitreous

it is a result of a pressure gradient from the anterior to posterior pole of the eye

28

is bulk flow a significant way to distribute low molecular weight substances in the vitreous

no

29

what type of molecules move with bulk flow

large, high molecular weight substances

30

what disolves and replaces the gel structure

aqueous lacunae: small pockets of liquid (melt together over time and creates a detachment)

31

why does the apparent molecular weight of vitreous collagen increase with age

because of the formation of new covalent cross-links between the peptide chains