Zones and Composition of the Vitreous

Question 1

The vitreous is divided into zones based on what

Answer 1

Based on the relative density of collagen

Question 2

Other names for the hyaloid channel/canal

Answer 2

Cloquet’s canal, or retrolental tract

Question 3

What are the three zones of the vitrous

Answer 3

The innermost- hyaloid canal/cloquet’s canal composed of primary vitreous
The intermediate- Composed of secondary vitreous that developed after primary vitreous.
The cortex- Outermost zone composed of secondary vitreous. Collagen fibrils are tightly packed.

Question 4

Hyaloid canal extends from

Answer 4

Bergmen’s channel to the Area of Martegiani. S shape manner.

Question 5

Hyaloid canal at 5 weeks vs 3 months gestation

Answer 5

5 weeks- composed of primary vitreous (hyaloid artery and collagen fibrils) Carried blood and nutrients to the lens prior to the production of the aqueous humor

3 months- Primary vitreous atrophies with development of secondary vitreous.

Question 6

What happens if the primary vitreous does not fully regress?

Answer 6

Remnants may be seen.

Mittendorf’s dot- on the back of the lens - no affect to vision
Bergmeister’s papilla- on the optic disc - no affect to vision
Rarely the entire artery would be seen - this would affect vision

Question 7

the 3 most abundant vitreous substances

Answer 7

99% is water
The majority of the remaining 1% is collagen. Mainly type II
The second most of the 1% is hyaluronate

Question 8

Main type of collagen in the vitreous and the other 2 types

Answer 8

Type II is the main type
Some collagen type 9 is used to link type II fibrils together
Some collagen type 10/11 integrated with type II

Question 9

Highest density to lowest density of collagen is located where in the vitreous

Answer 9

Highest density

Posterior cortex
Anterior cortex
Central vitreous

Lowest density

Question 10

Does collagen in the vitreous regenerate

Answer 10

No

Question 11

Two most common types of GAGs/proteoglycans in the vitreous

Answer 11

1. Hyaluronate acid
   - Next abundant substance next to collagen (not including water)
   - Fills the space between collagen fibrils and helps maintain transparency and saving.
   - Creates GEL STRUCTURE
2. Chrondroitin sulfate
   - Found at lower concentrations than hyaluronate acid
   - Linked to core protein, forming proteoglycans.
   - Helps maintain spacing between collagen fibers

Question 12

What is responsible for making the vitreous have gel consistency?

Answer 12

Hyaluronate acid

Question 13

Cells of the vitreous

Answer 13

Hyalocytes (90%) and Fibroblasts (10%- Their role is to produce collagen. Since there is low collagen turn over in the vitreous, not many fibroblasts are needed)

Question 14

___% of the cells in the vitreous are called hyalocytes

Answer 14

90%

Question 15

Role of hyalocytes

Answer 15

• Primarily in the vitreous cortex
• More numerous in fetal vitreous than adults (think they play a role in the hyaloid artery regression)
• Function in adults is unclear. Possibly synthesize hyaluronic acid or have phagocytic properties

Question 16

Where are hyalocytes and fibroblasts mainly loacted

Answer 16

Hyalocytes- Cortex

Fibroblasts- Vitrous base (at Ora Serata) and optic disc

Question 17

Concentrations of what in the vitreous differ from concentrations in the blood

Answer 17

Inorganic salts (K+, Na+, Cl-, Mg2+, Ca2+, and phosphate)
and Organic substances (Ascorbate/Vitamin C, glucose and galactose)

Question 18

Why are levels of ascorbate so high in the vitreous compared to the blood?

Answer 18

Ascorbate/Vitamin C is an antioxidant and neutralizes free radicals to prevent oxidation of the retina.

Question 19

A GAG is composed of

Answer 19

Polysaccharide. Composed of repeating disaccharide units