Aqueous And Vitrous Humor Flashcards
What is aqueous humor?
Clear, slightly alkaline liquid that occupies anterior and posterior chambers
How is aqueous humor similar and different from blood plasma?
Aqueous humor has LESS protein and glucose, but MORE lactic and ascorbic acid
What is the function of aqueous humor?
Provide nutrients, mostly oxygen, to avascular cornea and lens
Where is aqueous humor produced?
In the pars plicata and secreted through NPCE into the posterior chamber
What is the point of ascorbic acid?
It is a water soluble vitamin (C) that helps in fighting bacteria and detoxifying and also assists in the formation of collagen
What is the volume of aqueous humor? What rate is it replaced?
0.2 microliters, replaced every 100 minutes
What are the 5 main components of aqueous humor?
- bicarbonate
- lactic acid
- ascorbic acid
- chlorides
- glucose
What is the difference in aqueous humor between healthy eye and pathology? In cataract?
NONE, BITCH
What is the composition of vitreous humor?
-transparent liquid of salts, soluble protein, and hyaluronic acid contained within a meshqork of collagen
What is the primary part of vitreous humor?
Waterrrrrrrrrrr
How would someone describe vitreous humor?
Connective tissue status AND extracellular matrix
What are the main metabolites in vitreous humor that would help treat age related retinal degernation?
- magnesium serum
- copper serum
- zinc serum
- selenium serum
Where is vitreous humor said to be produced?
Pars plana NPCE
Where is the collagen content in the vitreous highest? What’s the order then?
Highest at base, then in posterior cortex, then anterior cortex, and lowest in the center
Why is the vitreous humor transparent?
Uniform collagen fibrils (8-16mm)
What types of collagen are found in the vitreous humor? Amounts?
- type II: fibril forming, 60-75%
- Type IX: 25%
- Type XI: 10%, combines with type II to make the core of the heterotypic fibrils
How much more ascorbic acid is in the vitreous than the plasma?
40 times more in vitreous
Name the 6 non-collagen components of vitreous
- fibrillin
- opticin
- GAGs
- hyaluronic acid
- hyalocytes
- fibroblasts
What is the purpose of fibrillin? What disease is associated with it?
- major structural component of zonules
- probably enforce collagen
- marfans is caused by mutation of Fibrillin-1 and can result in ectopic lens
What is opticin? Purpose?
- member of family of extracellular matrix, LEUCINE RICH repeat protein
- binds growth hormones and GAGs
Tell me about GAGs and vitreous
- GAGs are associated with water
- GAG content is highest in the vitreous because it has the most water (next highest is cornea, then sclera)
As GAGs are related to water, what is hyaluronic acid related to?
Collagen. More collagen means more HA
What is the purpose of hyaluronic acid in vitreous? Where is the highest concentration of HA?
- it is located within the collagen fibrils to maintain wide spacing of fibrils
- the interaction of HA with collagen makes the vitreous more gel like
- highest concentration is in the posterior cortex and he amount decreases centrally and anteriorly
How is HA different from a normal GAG?
-it is not linked to a core protein like normal GAGs and it is never sulphated
What happens to the amount of HA as we age?
We lose it so the gel becomes more liquid
What are hyalocytes?
Vitreous cells that are thought to make HA
What is the purpose of hyalocytes?
- building: making glycoproteins for collagen
- Eating: phagocytic properties
Where are hyalocytes located?
In a single wide spread layer in the cortex near the vitreal surface and parallel to it
Where do the hyalocytes do their functions?
- build more when anterior to the ora serrata
- eat more when posterior to the ora serrata
Where are the fibroblasts located? What is their purpose?
- located in vitreous base near ciliary body and near optic disc
- synthesize collagen fibrils
What are the four functions of vitreous humor?
- Physical support to hold the retina in place near the choroid
- Storage area for metabolites and a path to exchange metabolites
- Shock absorber for retina
- Transmit and refract light to help retina focus light
What are floaters?
- collagen fibrils coalescing when HA around collagen starts to degenerate
- light hits the condensations of collagen and creates a shadow
