WordNet

a thin pliable sheet of material
a pliable sheet of tissue that covers or lines or connects the organs or cells of animals or plants (同)tissue layer
relating to or secreting synovia
viscid lubricating fluid secreted by the membrane lining joints and tendon sheaths etc. (同)synovial_fluid

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(生物の)膜,皮膜

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/08/05 11:29:42」(JST)

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Synovial membrane (also known as synovium or stratum synoviale)^[1] is the soft tissue found between the articular capsule (joint capsule) and the joint cavity of synovial joints.^[2]

The word "synovium" is related to the word "synovia" (synovial fluid), which is the clear, viscous, lubricating fluid secreted by synovial membranes. The word "synvovia" or "sinovia" was coined by Paracelsus,^[3] and may have been derived from the Greek word "syn" ("with") and the Latin word "ovum" ("egg") because the synovial fluid in joints that have a cavity between the bearing surfaces is similar to egg white.

Structure

Synovium is very variable but often has two layers

The outer layer, or subintima, can be of almost any type: fibrous, fatty or loosely "areolar".

The inner layer, or intima, consists of a sheet of cells thinner than a piece of paper.

Where the underlying subintima is loose, the intima sits on a pliable membrane, giving rise to the term synovial membrane.

This membrane, together with the cells of the intima, provides something like an inner tube, sealing the synovial fluid from the surrounding tissue (effectively stopping the joints from being squeezed dry when subject to impact, such as running).

The surface of synovium may be flat or may be covered with finger-like projections or villi, which, it is presumed, help to allow the soft tissue to change shape as the joint surfaces move one on another.

Just beneath the intima, most synovium has a dense net of small blood vessels that provide nutrients not only for synovium but also for the avascular cartilage.

In any one position, much of the cartilage is close enough to get nutrition direct from synovium.

Some areas of cartilage have to obtain nutrients indirectly and may do so either from diffusion through cartilage or possibly by 'stirring' of synovial fluid.

The intimal cells are of two types, fibroblasts and macrophages, both of which are different in certain respects from similar cells in other tissues.

The fibroblasts manufacture a long-chain sugar polymer called hyaluronan, which makes the synovial fluid "ropy"-like egg-white, together with a molecule called lubricin, which lubricates the joint surfaces. The water of synovial fluid is not secreted as such but is effectively trapped in the joint space by the hyaluronan.

The macrophages are responsible for the removal of undesirable substances from the synovial fluid.

Synovial cell

Synovial cell	Resemble	Prominent organelle	Function
Type A	Macrophage	Mitochondria	Phagocytosis
Type B	Fibroblast	Endoplasmic reticulum	Secrete hyaluronic acid, & proteins complex (mucin) of synovial fluid

Mechanics

Although a biological joint can resemble a man-made joint in being a hinge or a ball and socket, the engineering problems that nature must solve are very different because the joint works within an almost completely solid structure, with no wheels or nuts and bolts.

In general, the bearing surfaces of manmade joints interlock, as in a hinge. This is rare for biological joints (although the badger's jaw interlocks).

More often the surfaces are held together by cord-like ligaments. Virtually all the space between muscles, ligaments, bones, and cartilage is filled with pliable solid tissue. The fluid-filled gap is at most only a twentieth of a millimetre thick. This means that synovium has certain rather unexpected jobs to do. These may include:

Providing a plane of separation, or disconnection, between solid tissues so that movement can occur with minimum bending of solid components. If this separation is lost, as in a 'frozen shoulder', the joint cannot move.
Providing a packing that can change shape in whatever way is needed to allow the bearing surfaces to move on each other.
Controlling the volume of fluid in the cavity so that it is just enough to allow the solid components to move over each other freely. This volume is normally so small that the joint is under slight suction.

Pathology

Synovium can become irritated and thickened in conditions such as synovitis or rheumatoid arthritis. When this happens, the synovium can become a danger to the bearing surface structure in a variety of ways. Excess synovial fluid weeping from inflamed synovium can provide a barrier to diffusion of nutrients to cartilage. The synovial cells may also use up nutrients so that the glucose level in the tissue is almost zero. These factors may lead to starvation and death of cartilage cells. Synovial cells may also produce enzymes that can digest the cartilage surface, although it is not clear that these will damage cartilage with healthy cells.

References

^ synovial+membrane at eMedicine Dictionary
^ "Medcyclopaedia - Synovial membrane". Archived from the original on 2012-02-05. Retrieved 2008-01-29.
^ The American Heritage Dictionary of the English Language

Edwards JCW (2003). "Chapter 17". In Klippel, John H.; Hochberg, Marc C. Rheumatology. St. Louis: Mosby. pp. 159–68. ISBN 0-323-02404-1.

UpToDate Contents

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1. 滑液検査および化膿性関節炎の診断 synovial fluid analysis and the diagnosis of septic arthritis
2. 慢性関節リウマチにおける滑膜異常 synovial pathology in rheumatoid arthritis
3. 水疱性類天疱瘡および粘膜類天疱瘡の疫学および病因 epidemiology and pathogenesis of bullous pemphigoid and mucous membrane pemphigoid
4. 水疱性類天疱瘡および粘膜類天疱瘡の臨床的特徴および診断 clinical features and diagnosis of bullous pemphigoid and mucous membrane pemphigoid
5. 敗血症性ショック：小児における蘇生後の継続的マネージメント septic shock ongoing management after resuscitation in children

English Journal

Functional role of the KCa3.1 potassium channel in synovial fibroblasts from rheumatoid arthritis patients.

Friebel K1, Schönherr R, Kinne RW, Kunisch E.
Journal of cellular physiology.J Cell Physiol.2015 Jul;230(7):1677-88. doi: 10.1002/jcp.24924.
Rheumatoid arthritis synovial fibroblasts (RA-SFs) show an aggressive phenotype and support joint inflammation and tissue destruction. New druggable targets in RA-SFs would therefore be of high therapeutic interest. The present study shows that the intermediate-conductance, calcium-activated potassi
PMID 25545021

Efficacy of parenteral administration of bee venom in experimental arthritis in the rat: A comparison with methotrexate.

Yamasaki SC1, Mendes MT2, Alponti RF2, Silveira PF3.
Toxicon : official journal of the International Society on Toxinology.Toxicon.2015 May;98:75-88. doi: 10.1016/j.toxicon.2015.02.016. Epub 2015 Feb 26.
The use of bee venom (BV) to treat inflammation and pain in arthritis has become increasingly common. This study aimed to compare the effects of BV and methotrexate (MTX), the most used disease-modifying anti-rheumatic drug, in arthritic rats. Edema, erythema, cyanosis, hyperalgesia, reduction of th
PMID 25727381

On the Anatomy of the Temporomandibular Joint and the Muscles That Act Upon It: Observations on the Gray Whale, Eschrichtius robustus.

El Adli JJ1, Deméré TA.
Anatomical record (Hoboken, N.J. : 2007).Anat Rec (Hoboken).2015 Apr;298(4):680-90. doi: 10.1002/ar.23109. Epub 2015 Mar 3.
The temporomandibular joint and its associated musculature are described in a neonate gray whale (Eschrichtius robustus) and serve as the basis for direct anatomical comparisons with the temporomandibular region in other clades of baleen whales (Mysticeti). Members of the right whale/bowhead whale c
PMID 25737135