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Synovial membrane
Black is subintima, purple is intima, light brown is bone, orange is cartilage, yellow is synovial fluid
Synovial joint
Latin membrana synovialis capsulae articularis
Gray's subject #68 282
Dorlands/Elsevier m_08/12522248

Synovial membrane (or synovium)[1] is the soft tissue that lines the non-cartilaginous surfaces within joints with cavities (synovial joints). Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Introduction ( Joints or Articulations Sutural ligament Fibrocartilages Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group Tissue is a cellular organizational level intermediate between cells and a complete organism Cartilage is a type of dense Connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix A joint is the location at which two or more Bones make contact Synovial joints (or diarthroses, or diarthroidal joints) are the most common and most moveable type of Joints in the human body [2]

The word "synovium" comes from a Latin word meaning "with egg," because the synovial fluid in joints that have a cavity between the bearing surfaces is like egg white. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. Synovial fluid is a thick stringy fluid found in the cavities of Synovial joints With its egg-like consistency ("synovial" partially derives from ovum, Albumen redirects here For other uses see Albumen (disambiguation.

Contents

Structure

Synovium is very variable but often has two layers.

Where the underlying subintima is loose the intima sits on a pliable membrane, giving rise to the term synovial membrane. MembraneA biological membrane or biomembrane is an enclosing or separating Amphipathic layer that acts as a barrier within or around a cell.

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 being squeezed dry when subject to impact, such as running).

The intimal cells are of two types, fibroblasts and macrophages, both of which are different in certain respects from similar cells in other tissues. A fibroblast is a type of cell that synthesizes and maintains the Extracellular matrix of many Animal tissues Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that

The surface of synovium may be flat or may be covered with finger-like projections or villi, which probably help to allow the soft tissue to change shape as the joint surfaces move one on another. Villus ( Latin: "shaggy hair" plural villi) can refer to Intestinal villus.

Just beneath the intima most synovium has a dense net of small blood vessels which provide nutrients not only for synovium, but also for the avascular cartilage. The blood vessels are part of the Circulatory system and function to transport Blood throughout the body A nutrient is food or chemicals that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment

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, although the film is very thin.

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. Joint replacement is one of the most common and successful operations in modern Orthopaedic surgery. A hinge is a type of bearing that connects two solid objects typically allowing only a limited angle of Rotation between them A ball and socket joint ( enarthrosis, spheroidal joint) is a Joint in which the distal bone is capable of motion around an indefinite number of axes

In general the bearing surfaces of man made joints interlock, as in a hinge. This is rare for biological joints (although the badger's jaw interlocks). Badger is the Common name for any animal of three subfamilies which belong to the family Mustelidae: the same Mammal family as the

More often the surfaces are held together by cord-like ligaments. In Anatomy, the term ligament is used to denote three different types of structures Fibrous tissue that connects Bones to other bones Virtually all the space between muscles, ligaments, bones and cartilage is filled with pliable solid tissue. Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce The fluid-filled gap is mostly only a twentieth of a millimetre thick. This means that synovium has certain rather unexpected jobs to do. These may include:

  1. 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.
  2. Providing a packing that can change shape in whatever way is needed to allow the bearing surfaces to move on each other.
  3. 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 rheumatoid arthritis. Rheumatoid arthritis ( RA) is a chronic systemic autoimmune disorder that causes the Immune system to attack the Joints, where 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. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. These factors may lead to starvation and death of cartilage cells. Synovial cells may also produce enzymes which can digest the cartilage surface, although it is not clear that these will damage cartilage with healthy cells. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins

See also

References

  1. ^ eMedicine/Stedman Medical Dictionary Lookup!. A synovial sheath is a a layer of a Tendon sheath containing Tendons in the hand and foot Retrieved on 2008-01-29. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 904 - Sergius III comes out of retirement to take over the papacy from the deposed Antipope Christopher.
  2. ^ Medcyclopaedia - Synovial membrane. Retrieved on 2008-01-29. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 904 - Sergius III comes out of retirement to take over the papacy from the deposed Antipope Christopher.

Dictionary

synovial membrane

-noun

  1. (anatomy) A thin membrane of joints, comprised of smooth connective tissue and which secretes synovial fluid.
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