Physiology of Joints Flashcards
what are the three types of joint in the body
synovial
fibrous
cartilaginous
describe fibrous joints (synarthrosis) and give an example of one
when bone are united with fibrous tissue, dont allow movement
bones of the skull in adults
describe cartilaginous joints (amphiarthrosis) and give 5 examples
bones united by cartilage, allow little movement
intervertebral discs
pubic symphsis
part of the sacroiliac joints
costochondral joints
describe synovial joints (diarthrosis)
when bones are separated by a cavity (containing synovial fluid) and united by a fibrous capsule (+ other extra articular structures: ligaments, tendons and bursae)
what lines the inner aspect of a synovial fibrous capsule
synovial membrane (60 microM thick)
what is the synovial membrane
vascular connective tissue with capillary networks and lymphatics
what does the synovial membrane contain that produces synovial fluid
fibroblasts (synovial cells)
what covers the articular surfaces of bones in synovial joints
cartilage
describe the two types of synovial joints
simple- one pair of articular surfaces
compound- more than one pair of articular surfaces (e.g elbow)
what extra articular surfaces support joints
ligaments, tendons and bursae
what are the physiological functions of joints
to serve the functional requirements of the MKS
structural support and purposeful movement
what is an additional role of the joint during purposeful movement
stress distrubution
how does the joint remain stable
the shape of the articular component
ligaments stabilise
synovial fluid acts as an adhesive seal that freely permits sliding motion between cartilaginous joints
what provides joint lubrication
cartilage interstitial fluid
synovium- derived hyaluronic acid (mucin- a polymer of disaccharides)
synovium- derived lubrcin (a glycoprotein)
what are the 6 roles of synovial fluid
lubricates joint
facilitates joints movements (reduced friction)
help minimise wear and tear
aids in the nutrition of articular cartilage
supplies the chondrocytes (cartilage cells) with O2 and nutrients
removes Co2 and waste products
what does the synovial fluid fill
the joint cavity
is the synovial fluid a static pool- explain
no- synovial fluid is continuously replenished and absorbed by the synovial membrane
why does synovial fluid have a high viscosity
due to the presence of hyaluronic acid (mucin) produced by the synovial cells
does the viscosity of synovial fluid vary
yes, with joint movement
what role does the blood play in synovial fluid
constituents such as uric acid are derived from by dialysis of blood plasma
what cells are contained within the synovial fluid
not many- mostly mononuclear leucocytes
<200 WBC/mm3 (0f which polymorphs are usually <25/mm3)
what happens to the synovial fluid during joint movement (especially rapid movement)
the viscosity and elasticity change
rapid movement=
viscosity descreased
elasticity increased
what properties of synovial fluid become defective in diseased joints (e.g. osteoarthritis)
its ability to decrease in viscosity and increase in elasticity during rapid movement
what does synovial fluid look like
clear and colourless
when does synovial blood count increase from more than <200WBC/mm3
in inflammatory and septic arthritis
when does synovial fluid turn red
in traumatic synovial tap and in haemorrhagic arthritis
when does synovial fluid go straw to yellow colour
inflammatory synovial fluid
when does synovial fluid go opaque
septic synovial fluid
when, other than during movement, is synovial viscosity low
inflammatory synovial fluid
when is synovial fluid total cell count highest
septic synovial fluid
what are the roles (2) of articular cartilage
provides a low friction lubricated gliding surface which helps prevent wear and tear of joints
distributes contact pressure to subchodral bone
what plays a key role in determining the mechanical properties of cartilage
the composition of the cartilage ECM and the interaction between the fluid and solid phase of the cartilage
list the different zone of articular cartilage from outwards to inwards
articular surface superficial zone middle zone deep zone calcified zone (subchondral bone)
what do the zones of articular cartilage differ in
organisation of collagen fibres and relative content of cartilage components
what type of cartilage is articular cartilage usually
hyaline
describe the properties of articular cartilage
elastic and spongey
what parts of bone does the articular cartilage cover
articular surfaces
what makes up the extracellular matrix of articular cartilage
water (70%)
collagen (20%, mainly type II, contributes to the elastic behaviour)
proteoglycans (10%)
describe 4 key properties of water in cartilage
70% of cartilage wet weight
unevenly distributed, 80% near articular surface
content decreases with age
maintains the resiliency of the tissue and contributes to the nutrition and lubrication system
describe 5 key properties of collagen in cartilage
20% of wet weight
mainly type II
decreases with age
maintain cartilage architecture
provides tensile stiffness and strength
describe the 5 key properties of proteoglycan
10% of cartilage wet weight
highest concentration in middle and deep zone
composed mainly of glycosaminoglycan e.g. chondroitin sulphate
composition changes with age (chondroitin decreases with age)
responsible for the compressive properties associates with load bearing
how much of cartilage volume is ECM (extracellular matrix)
> 98% of cartilage volume
what synthesises, degrades and maintains the ECM
chondrocytes (usually <2% of the total cartilage volume)
how does articular cartilage and chondrocytes receive nutrients and O2
articular cartilage is avascular- gets it from synovial fluid
how does the rates of ECM degradation and replacement compare in normal joints
degradation doesn’t exceed replacement
how do chondrocytes degrade ECM components (e.g. collagen and proteoglycan)
metalloproteinase PROTEOLYTIC ENZYMES
e.g. collagenase and stomelysin
what can change the mechanical properties of the knee
changes in the relative amounts of the components (water, collagen and proteoglycans)
or
if ECM degradation exceed rate of synthesis
what do the catabolic factors of cartilage matrix turnover do, give 2 examples of them
stimulate proteolytic enzymes and inhibit proteoglycan synthesis
TNF alpha
Interleukin - 1
what do the anabolic factors of cartilage matrix turnover do, give 2 examples of them
stimulate proteoglycan synthesis and counteract effects of IL-1
tumour growth factor (TGF- beta)
insulin like growth factor (IGF-1)
what are the two markers of cartilage degradation and why are they present
serum and synovial keratin sulphate
- increased levels indicate cartilage breakdown
- level increses in patients with osteoarthritis
type II collagen in synovial fluid
- increased levels indicate cartilage breakdown
- useful in evaluating cartilage erosion (e.g. in osteoarthritis and rheumatoid arthritis)
what is osteoarthritis caused by
cartilage and synovial composition and function deteriorate with age and repeated wear and tear
what causes rheumatoid arthritis
synovial cell proliferation and inflammation
what causes gouty arthritis
deposition of salt crystals (e.g. uric acid) in the joint
what causes soft tissue rheumatism
injury and inflammation to periarticular structures (e.g. injury to tendon causes tendonitis
what effects on the bone can be seen following cartilage wear and tear
cyst formation
sclerosis in subchondral bone
osteophyte formation
what shaped needles in gouty arthritis
needle shaped
what type and shape of needles in pseudo gout
rhomboid shaped calcium pyrophosphate crystals
