Viscosity of synol fluid depends upon:

D i.e. Hyaluronic acid- The viscosity and the plastic (thixotropic propeies) of the synol fluid is because of its hyaluronate content.Q- Hyaluronic acid, a glycosaminoglycan is a polymer of repeating disaccharide units (of glucuronic acid and N-acetyl glucosamine).Proteoglycans & GlycosaminoglycansProteoglycans are protein that contain covalently linked glycosaminoglycans. Examples are syndecan, betaglycan, serglycan, perlecan, aggrecan, versican, decorin, biglycan & firomodulin.The protein of PG that bound covalently to glycosaminoglycans are called core proteins. It is synthesized in endoplasmic reticulum and few GAG linkage also form here. Most of later GAG chains & modification occur in golgi apparatus.- An 0- glycosidic bond between xylose (Xyl) & ser is unique to proteoglycans.- The amount of carbohydrate in PG is usually much greater than found in glycoproteins & may be upto 95% - Aggrecan is found in cailageQGlycosaminoglycans (GAG) is an unbranched polysacehride made up of repeating disaccharides, one component of which is always an amino sugar, either D- glucosamine (Glc-N), or D- galactosamine (Gal-N). The other component (except in case of keratan sulfate) is uronic acid either L-glucronic acid (Glc-UA) or its 5'epimer, L- iduronic acid (Id- UA) 7 types of GAGs are - hyaluronic acid, chondroitin sulfate, keratan sulfates I & II, heparin, heparan sulfate & dermatan sulfate- With exception of hyaluronic acid, all GAGs contain sulfate groups, either as 0- esters or N- sulfate ( in heparin & heparan sulfate). Hyaluronic acid affords another exception because there is no clear evidence that it is attached covalently to protein.Functions of GlycosaminoglycansHyaluronicacid- Viscosity of the synol fluidQ.- Tensile strength and elasticity ofcailage and tendons- Jelly like consistency of vitreoushumor of eyeQ.Chondroitinsulfate- Tensile strength of cailagetendons, ligaments and the walls ofaoa*.Dermatansulfate- Pliability of skin* and heavalves*.Keratansulfate- Found in horny structures* ofbody composed of dead cells ?hair, nails, claws, horn, hoofs.- Also present in cornea*.Heparin- Anti coagulantMajor proteins of GlycosaminoglycansGAGSugarsSulfateLinkage ofproteinLocationHAGIcNAc,GIcUANilNo firmevidenceSynol fluid,vitreous humor,loose connectivetissueCSGaINAc,GIcUAGaINAcXyl-ser;assoiatedwith HA linkproteinsCailage, bone,corneaKS IG1cNAc,GalGIcNAcGIcNAc-AsnCorneaKS IIGIcNAc,GalSame asKS IGaINAc-ThrLoose connectivetissueHeparinGIcN,IdUAGIcNG1cNSerMast cell IdUA HeparansulfateG1cN,GIcUAGIcNXyl-SerSkin fibroblasta,aoic wallDermatansulfateGaINAc,IdUA,(G1c.UA)GaINAcIdUaXyl-SerWidedistribution