Vitreous humour

Vitreous humour
1. Vitreous Humour
2. General features  Vitreous humour is an inert ,transparent , colourless, jellylike, hydrophilic gel that serves the optical functions and also acts as important supporting structures for the eyeball.  The vitreous cavity is bounded by anteriorly by the lens and ciliary body and posteriorly by the retina  Its weighs nearly 4g  Vitreous is an extacellular material composed of approximately 99 per cent water
3. Structure  The vitreous body is the largest and simplest connective tissue present as a single piece in the human body  Divided into three parts- 1. The hyaloid layer or membrane 2. The cortical vitreous and 3. The medullary vitreous

1. Vitreous Humour

2. General features Vitreous humour is an inert ,transparent , colourless, jellylike, hydrophilic gel that serves the optical functions and also acts as important supporting structures for the eyeball. The vitreous cavity is bounded by anteriorly by the lens and ciliary body and posteriorly by the retina Its weighs nearly 4g Vitreous is an extacellular material composed of approximately 99 per cent water

3. Structure The vitreous body is the largest and simplest connective tissue present as a single piece in the human body Divided into three parts- The hyaloid layer or membrane The cortical vitreous and The medullary vitreous

4. 1.Hyaloid layer It is not a true membrane but the outermost surface of vitreous It has a structure of connective tissue and shows fibrils which run parallel with the surface It has two layers 1.Anterior hyaloid membrane 2. Posterior hyaloid membrane

5. 2.Cortical vitreous It lie in peripheral zone approx 100 micron in width It is more condensed fibrillar vitreous It contain type two collagen fibrils interspersed with the sodium hyaluronate mucopolysaccharides molecules , which provides a viscosity, and elasticity 2 percent of the total vitreous volume 3.Medullary vitreous Majority of the vitreous body is formed by the central medullary vitreous Similar to the cortical vitreous except it is a less fibrillar structure and cell free

6. function Screen out UV and IR light Provide a clear media for optical transmission Protection of the media

7. composition The vitreous body is composed of three major structural components : Water Collagen- like fibers , Hyaluronic acid a glycosaminoglycans ( GAGs) Collagens gives the vitreous its substance and the sodium hyaluronate provides the viscoelasticity The human vitreous is typically gel 1.composed of randomly arranged collagen fibers and soluble hyaluronic acid 2. collagen : the protein of the vitreous is called vitrosin 3. determined to be collagen for several reason :

8. has the amino acid hydroxyproline which is specific to collagen Has the same X-ray diffraction properties as collagen Normal ionic composition : the vitreous, except for collagen and sodium hyaluronate , is very similar to the aqueous (a) oxygen : the oxygen in the vitreous comes from the arteries of the retina (b) water : the water in the vitreous is exchanged about every 30 min. _ water movement of 85 mm3/min Sodium – enters anteriorly from the ciliary body and posterior chamber - 90% of the sodium in the vitreous is exchanged in 24 hrs, mainly flows to the aqueous

9. Potassium 1 . Enters by active transport through the ciliary epithelium into the posterior chamber 2 . Diffuses into the vitreous from lens and posterior chamber 3 . Exists through the retina Chloride There is a gradient of chloride from the vitreous to the aqueous it is removed by retina and the posterior chamber

10. Phosphate Enters the vitreous via ciliary body Low concentration in the vitreous because is used by the retina If retina damaged , conc. o f phosphate goes up in vitreous Glucose Glucose diffuses into the vitreous from all the tissues Protein The blood – vitreal barrier blocks the movement of most protein into the vitreous