structure and function of joints Flashcards
what do joints do? (3)
- transmit load
- allow movement
- provides stability
what are the three main classes of joints? (6)
- fibrous joints - immobile (synarthrosis)
- cartilaginous joints - slightly mobile (amphiarthosis)
- synovial joints - freely mobile (diartrhosis)
what are examples of fibrous joints? (2)
skull sutures, tooth sockets
what is an example of a cartilaginous joint?
intervertebral disc (annulus fibrous surrounds the nucleus pulpous)
example of synovial joints
limb joints
saddle joint movement done by… (synovial joints)
carbo-metacarpal, base of thumb
examples of synovial joint movements
simple hinge joint, complex hinge joint, pivot joints, saddle joints, ball and socket
what is a property of ball and socket joints?
most mobility but least stability
5 ways to achieve stability of a joint
- needs to be congruity
- fibrous capsule provides more stability
- intra-articular ligaments
- packing improves congruity
- muscle acting across joint improves stability drastically.
properties of articular cartilage
avascular and aneural - sol takes longer to repair itself
how does the cartilage get nutrients?
through the synovial fluid from the synovium.
what are the stretch receptors used for?
proprioception
what do stimulation of nociceptors by arthritic effusion cause?
reflex muscle inhibition - overtime leads to muscle wasting in arthritis
whats the main chemical that gives cartilage its properties?
GAG - glucosamine-glycan chain
GAG + core protein =
proteoglycan (AGGRECAN)
what does aggrecan do?
produces a huge osmotic pressure that inflates cartilage with water (gel swelling pressure)
what does hyaluronan do
tethers the aggrecan molecules together
what type of collagen fibres hold everything together?
type 2
Whats the only cell type in cartilage?
chondrocytes
what do chondrocytes do?
produces,
- collagen
- proteoglycans
- hyaluronan
how are the nutrients in the synovial fluid pushed into the cartilage?
diffusion
what types of synoviacytes help secrete hyaluronon an lubricant?
type B
what other cells are sometimes there in synovial lining?
macrophages
what provides fluid drainage
synovium on the outside has interstitial matrix and there is contact between the interstitial matrix and synovial fluid.
what is a property of plasma
ultrafiltrate
what is the electrolyte and plasma protein content of synovial fluid similar to?
other interstitial fluids
what is lubricin
glycoprotein
high load and low velocity (boundary lubrication)
hyaluronan (3)
non sulphated GAG
high load and low velocity (hydrodynamic lubrication)
buffers fluid loss from joints
what is joint effusion
when fluid increase 10 - 100x in arthritis
how is the pressure in extension?
sub atmospheric (fluid enters) (synovial fluid is made)
how is the pressure in flexion?
above atmosphere (fluid is driven out) (goes into lymphatic drainage)
how does the rate of fluid loss change with hyaluronan?
fluid drainage (on flexion) in absence of hyaluronan is much higher than when hyaluronan is present.
what is arthritis
inflammation of joint
what is arthritis characterised by (3)
- pain
- swelling
- loss of movement
what are the two types of arthritis
- acute
2. chronic (immune mediated, degenerative, e.g. osteoarthritis)
properties of osteoarthritis (3)
- metabolic changes in joint, evidence of cartilage loss
- associated with again, mechanical dysfunction, obesity
- can be synovial inflammation
properties of inflammatory arthritis (3)
- cytokines and other inflammatory mediators released by synovium
- autoimmune mechanism (rheumatoid)
- damage of cartilage by inflammatory response
