Synovial Membrane (aka synovium) and Synovial Fluid · Mesotendon transmits blood vessels . Like a...
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BIOS1168 FMA Lecture Week 5 Dr Catherine Willis Synovial Membrane (aka synovium) and Synovial Fluid
Transcript of Synovial Membrane (aka synovium) and Synovial Fluid · Mesotendon transmits blood vessels . Like a...
BIOS1168FMA LectureWeek 5
Dr Catherine Willis
Synovial Membrane (aka synovium)
and
Synovial Fluid
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Do not remove this noticeUnlabelled Images used in these notes are taken from-
The Sourcebook of Medical Illustration, P Cull ed.The Parthanon Publishing Group Limited 1989Mediclip Human Anatomy 1, 2 & 3 Williams & Wilkins A Waverley Group 1996
Fundamentals of Anatomy and Physiology F. Martini 7th ed, Pearsons, 2006
Where do we find Synovial Membranes?
1. Part of Synovial Joints
Lining the joint capsule
Attaches to articular margin
2. Bursa, bursae
Sac like dilation
Lined with synovial membrane
Filled with synovial fluid
3. Tendon Sheaths
Bursae that have tendons embedded in them
Bursa
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When you die the synovial fluid diffuses out of your joints. Don't typically see the synovial membrane in the lab.
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Synovial membrane also known as synovium.Synovial membrane lines the joint capsule. Therefore described as attaching on to articular margins -- the bone on one side and connective tissue on the other. Varies in thickness -- in a normal situation it is very thin, in an abnormal situation it thickens up and has implications.
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Synovial membrane dilation that is seperate from the joint. Has a separate function.
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Tendons which turn corners and have to go and maintain a smooth kind of working -- eg the tendons in your hand… the same membrane but a different function
2. Bursa
Bursa
Synovial Fluid
- develops between * tendon and a bone * tendon and joint capsule * tendon and tendon* tendon and skin
limited attachment to the tendon
limited attachment to “the other”
Free areas at ends facilitate movement
Bursae come in a number of shapes and sizes
Synovial Fluid filled sac
Communicating or non communicating
Free area
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Develop in response to movement - anywhenre where a tendon is rubbing against another tissue --- protects the tendon from wearing out - preserves itAlso stops the bone from wearing out.If you don't move your bursa will get reabsorbed.
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Imagine a baloon full of water and rubbing it with your hand against a desk or surface… reduces tension and saves increase frinction
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Connected to the joint cavity
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independent of joint cavity
Posterior View
Synovial membrane of Glenohumoral joint
Non communicating bursaSubacromial Bursa
Examples
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Does not communicate with the joint cavity of the GHJ
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Bursitis -- swelling of a bursa -- ie when you rub your elbow on the desk == student's elbow
Synovial sac with tendon embedded
May be a single tendon Eg flexor digital sheaths
May be a number of tendons embeded into the same sheathEg common flexor synovial sheath
3. Synovial Sheaths
T
T
Visceral layer – next to tendon
Parietal layer- secured to surrounding structures
Mesotendon transmits blood vessels
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Like a bursa with a tendon embedded in it. -- Tendon develops separately from sac in utero but as the baby develops it moves towards the sac and embeds itself inside the sac, becoming completely enclosed in the sac.
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muscles, bones
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Mesotendon transmits the blood vessels that need to go up to supply the cells of the tendon itself.
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Structurally very delicate.
Flexor digital synovial sheath
Common flexor synovial sheath
Examples
1 tendon
2 tendon
8 tendons
Free edge
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Some contain just one tendon, some contain two and some contain 8.
Characteristics of Normal Synovial Fluid
Clear, Colorless to light yellow
High Viscosity – slipperiness
Thick fluid - Consistency of egg white
Ultrafiltrate of plasma
Diffuse from capillaries
i) Physical characteristics
ii) Mechanical properties
High Elasticity – deforms under pressure
iii) Major componentsHyaluronan (atypical PG) Viscous and elastic properties
Water Carries substances in solution
Small volume in any joint eg knee 3.5mL
Small plasma proteins Glucose and other nutrients
Lubricin (PG) lubricant attaches to articular surfaces
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Contained inside synovial joint and bursa
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Want it to be slippery to aid movement
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When weight bearing -- this is a good thing!
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PG =ProteoGlycan
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PG =ProteoGlycan
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Plasma proteins are normally found in blood
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Because they come from blood they must diffuse from capillariesUltrafiltrate of plasma … plasma is what found in blood vessel, but these things diffuse out of the blood vessel into the synovial fluid - hence the term ultrafiltrate
Structure of a synovial membrane
Synovial fluid
Capsule
i) IntimaLining cell layer 1-2 cells thick
• Collagen and reticular fibers
• Many Blood vesselsArterioles and venules
ii) Loose Connective tissue layer
Highly Folded thin membrane
• Fibroblasts + other cells
• Highly liquid ground substance
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Looks furry
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Fibroblast = cell that makes fibres
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interface b/w synovial fluid and synovial membrane -- great influence of what happens in the synovial membrane
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Lots of capillaries and veins and arterioles -- very vascular
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The stuff in b/w -- the glue that holds everything togetherhigh PG levels especially HYALURONAN
Specific Structural features of synovial membrane
Type BFibroblast like cell
Type A Macrophage like cells
Extrcellular matrix Fenestrated capillaries
Remove debris from the joint by phagocytosis
Monitor homeostatic mechanisms
produce hyaluronan Important part of synovial fluid
Blood nutrients and water diffusethrough the intercellular space, between cells into the joint cavity
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A is for appetite -- consume everything they come into contact with
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When one cell comes up to another and engulfs it … vacuum cleaners, PacMan of the synovial fluid
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Make sure it's well-regulated.
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B is for worker bees… they work all the time, producing Hyaluronan that is put into the synovial fluid. Extremely importantConstantly replacing themselves
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Like a window Little holes in them-- constant supply of nutrients and water coming in and then diffusing outThe health of the blood vessels influences what is happening in the synovial membrane
Mechanical makes synovial fluidwhich is the lubricant between moving surfaces within the joint
Metabolic delivers nutrients and metabolic waste products between blood and hyaline cartilage
Functions of a synovial membrane
Functional provide a smooth and non adherent surface to facilitates movement
Maintains synovial fluid - removal of debris
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Produced by cells in the previous slide
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Synovial membrane produces synovial fluid which affects the hyaline cartilage
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If you don't use it you lose it -- thins remarkably over time -- joints immobilised -- this is good for healing bone but not so good for the membrane
Normally Synovial Fluid has ..
NO leukocytes (white blood cells)
NO red blood cells
NO plasma clotting factors
NO culture (no bacteria)
NO chondrocytes
Little volume and NO Cells …SO there are ………….
Inflammation
haemarthrosis
Septic
Osteoarthritis Trauma
Effusion or edema
If these factors are present it indicates …..
Vascular dysfunction
NO Mast cells Inflammation
Disintergration of membrane NO Type A or Type B synovial cells
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Just fluid
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Contain inflammatory mediators
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should be contained to blood vessels
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Cartilage cells
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Should be confined to membrane
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How we describe a swollen joint
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haem = rbcs arthrosis = joint
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Indicates cartilage is breaking down
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Something is wrong with the membrane
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Problem with vessels .. they are leaking
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If you have bacteria living in the joint we describe it as septic
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If there is high levels of uric acid in the synovial fluid it is called Gout … causes swelling of joint and pain around the joint
Cellular Abnormalities of Synovial Membrane in inflammatory joint disease
Fibroblasts proliferate and produce more collagen – thickens membrane
Resident Mast cells degranulate –inflammatory mediators eg histamine
Intima Cells - Type A Macrophage like cells and Type B fibroblast like cellsbecome very stressed and die
Leukocytes migrate into membrane and participate in inflammatory response- Neutrophils- Monocytes- lymphocytes
Membrane becomes thickened and densely cellular All characteristic of acute inflammatory response
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Changes in the synovial membrane
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Gets clogged up
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increased in number
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Stops fluids from being able to move through easily, clogs it up
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Cellular nervous breakdown -- a call for help!Releases inflammatory mediators like histamines -- calls cells to the area
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The membrane is no longer getting oxygein and nutrients through it.
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An army moves in and occupies
Tissue Abnormalities of Synovial Membrane in inflammatory joint disease
• Membrane becomes thickened IMPLICATION Prevents normal movement of Water, small proteins, nutrients to the synovial fluid and removal of metabolic wastes from the synovial fluid.
• excessively vascularIMPLICATION Large proteins move from the vascular compartmentsinto the s. membrane and clog it up.
• densely cellularIMPLICATION Leukocytes and mast cells move in to the membrane and set up inflammatory processes to remove unwanted proteins or dead and dying cells
All characteristic of acute inflammatory response
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Can't find its way through
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Increased amount of metabolic waste in synovial fluid
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and more permeable -- in response to histamines
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A cycle… all these things happen to help fight the problem but may compound the problem -- trying to heal but makes it worse
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Synovitis = inflammation of synovial membranes
Abnormalities of Synovial Fluid in inflammatory joint disease
Increase amounts of synovial fluid within the joint –> swelling
Decrease hyaluronan content –> reduced viscosity and elasticity
Increased protein content – clotting of synovial fluid
Increased inflammatory cells – inflammatory response continues
Reduced nutrients –> damage / death to chondrocytes due to decrease nutrition and metabolic waste transfer
Cartilage fragments – damage to articular surface -> abrasions
1. Volume
2. Composition
3. Cellular Composition
Dead and dying cells – dislodged from membrane Type A and Type B cells
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Increased plasma proteins
Joint damage in inflammatory joint disease due to abnormalities in synovial fluid
Increase amounts of synovial fluid–> joint swelling –> stretching of ligaments ->Rupture of ligaments -> joint instability and deformation
Decrease hyaluronan content of synovial fluid – reduced viscosity & elasticity
Increased protein content – clotting of synovial fluid
Chondrocytes starved of nutrients and die
-> decreased protection of articular surfaces -> abrasions -> cartilage erosion
Decrease nutrition and metabolic waste transfer
Fragments of cartilage float in fluid -> abrasions of articular surfaces
