Editing Synovial fluid (section)

===Composition===
Synovial tissue is sterile and composed of vascularized connective tissue that lacks a basement membrane. Two cell types (type A and type B) are present: Type A is derived from blood monocytes, and it removes the wear-and-tear debris from the synovial fluid. Type B produces [[hyaluronan]]. Synovial fluid is made of [[hyaluronic acid]] and lubricin, proteinases, and collagenases. Synovial fluid exhibits [[non-Newtonian fluid|non-Newtonian flow]] characteristics; the viscosity coefficient is not a constant and the fluid is not linearly viscous.  Synovial fluid has anti-[[thixotropic]] characteristics; under conditions of sudden increase in pressure as in some kind of mechanical shock, its viscosity suddenly increases.<ref>< {{cite journal
 |title=Rheopexy of synovial fluid and protein aggregation |journal=Journal of the Royal Society Interface |author=Oates, Katherine |pmid=16849228 |doi=10.1098/rsif.2005.0086 |volume=3 |issue=6 |pmc=1618490 |year=2006 |pages=167–74}}</ref> Normal synovial fluid contains 3–4&nbsp;mg/ml [[hyaluronan]] (hyaluronic acid),<ref name=hui2012>{{cite journal
 |last1=Hui |first1=Alexander Y. |last2=McCart |first2=William J. |last3=Masuda |first3=Koichi |last4=Firestein |first4=Gary S. |last5=Sah |first5=Robert L.|date=Jan–Feb 2012|title=A Systems Biology Approach to Synovial Joint Lubrication in Health, Injury, and Disease |journal=Systems Biology and Medicine |series=Wiley Interdisciplinary Reviews |volume=4 |issue=1 |pages=15–7 |doi=10.1002/wsbm.157 |pmc=3593048 |pmid=21826801}}</ref> a polymer of [[disaccharide]]s composed of D-glucuronic acid and D-N-acetyl[[glucosamine]] joined by alternating beta-1,4 and beta-1,3 [[glycosidic bond]]s.<ref>{{cite journal |url=http://www.glycoforum.gr.jp/science/hyaluronan/HA01/HA01E.html |title=GlycoForum / Science of Hyaluronan |journal=Glycoforum |date=15 December 1997 |volume=1 |pages=A2 |last1=Hascall |first1=Vincent C. |last2=Laurent |first2=Torvard C. }}</ref>{{MEDRS|date=February 2013}} Hyaluronan is synthesized by the synovial membrane and secreted into the joint cavity to increase the viscosity and elasticity of articular cartilages and to lubricate the surfaces between [[synovium]] and cartilage.<ref>{{cite web |url=http://www.orthop.washington.edu/?q=patient-care/articles/arthritis/joints.html |publisher=University of Washington Medicine - Department of Orthopaedics and Sports Medicine |title=Joints |access-date=2013-02-04 |archive-date=2013-08-07 |archive-url=https://web.archive.org/web/20130807171425/http://www.orthop.washington.edu/?q=patient-care%2Farticles%2Farthritis%2Fjoints.html |url-status=dead }}</ref>{{MEDRS|date=February 2013}}

Synovial fluid contains [[PRG4|lubricin (also known as PRG4)]] as a second lubricating component, secreted by synovial [[fibroblast]]s.<ref name=jay2000>{{cite journal
 |last1=Jay |first1=GD |last2=Britt |first2=DE |last3=Cha |first3=CJ |date=March 2000 |title=Lubricin is a product of megakaryocyte stimulating factor gene expression by human synovial fibroblasts |journal=[[J Rheumatol]] |volume=27 |issue=3 |pages=594&ndash;600 |type=abstract |pmid=10743795 }}</ref>  Chiefly, it is responsible for so-called boundary-layer lubrication, which reduces friction between opposing surfaces of cartilage. There also is some evidence that it helps regulate synovial cell growth.<ref>{{cite journal |author=Warman M |journal=[[Arthritis Research & Therapy]] |year=2003 |volume=5 |issue=Suppl 3 |pages=5–7 |title=Delineating biologic pathways involved in skeletal growth and homeostasis through the study of rare Mendelian diseases that affect bones and joints |doi=10.1186/ar804 |doi-access=free |pmc=2833794 }}</ref>

It also contains [[Phagocyte|phagocytic cells]] that remove microbes and the debris that results from normal wear and tear in the joint.