Synovial joints Flashcards
Name & describe typical components of synovial joints
Articular capsule:
Surrounds joint & is continuous with periosteum of articulating bones
2 layers:
Fibrous layer (outer) - holds together articulating bones
Synovial layer (inner) - highly vascularised layer of serous connective tissue
Articular cartilage:
Articulating surfaces of synovial joint covered by thin layer of hyaline cartilage
Synovial fluid
List forces acting on synovial joints
Compression & tension in perpendicular orientation to articular surface
Shear force in parallel orientation to articular surface
Describe how different components of synovial joints contribute to joint movement
Articular cartilage minimises friction allowing smooth/easy movement
Articular capsule releases synovial fluid which is essential for movement & holds articulating bones together
Synovial fluid lubricates joint & absorbs shock
Explain role of cartilage & synovial fluid in reducing concussion
Cartilage cushions joint which absorbs shock, prevents friction & prevents wear & tear by cushioning bone ends
Synovial fluid – absorbs shock & prevents bones from hitting each other
What normal & abnormal biomechanical forces can lead to joint pathology?
Abnormal:
Obesity
Trauma
Malalignment
Joint instability
Abnormal anatomy
Normal:
Inflammation
Ageing
Sepsis
Genetic factors
Immune responses
Leads to:
Matrix damage
Increased catabolic activity
Aberrant repair response
Mechanical failure
What are the 2 types of synoviocytes
Type A
Macrophage like cells
Located in inner surface of joint cavity
Remove debris in synovial fluid through phagocytosis
Require mitochondria
Account for 25% of cells in synovial membrane
Type B
Fibroblast-like
Synthesize & secrete major extracellular matrix proteins in synovial fluid
Some possess mesenchymal stem cell properties & can be used as source of cells for cartilage repair
What are plane joints
Multiaxial joint
Articular surfaces flat
Only allow short nonaxial gliding movements
e.g. intercarpal & intertarsal joints
What are hinge joints
Uniaxial joint
Convex surface of one bone into concave of another
Motion is along single plane & resembles that of mechanical hinge
Permit flexion & extension only
e.g. elbow & interphalangeal joints
What are pivot joints
Uniaxial joint
Rounded end of one bone conforms to sleeve ring composed of bone on another
Uniaxial rotation of one bone around its own long axis
E.g. between vertebrae in neck
What are condyloid joints
Biaxial joint
Oval articular surface of bone fits into complementary depression another
Both articulating surfaces oval
Permit all angular motions (flexion/extension, abduction/adduction & circumduction)
e.g. radiocarpal (wrist) & metacarpophalangeal (knuckle) joints
What are saddle joints
Biaxial joint
Greater freedom of movement than condyloid joints
Each articular surface has both concave & convex areas
e.g. carpometacarpal joints of thumbs
What are ball & socket joints
Multiaxial joint
Spherical or hemispherical head of one bone articulates with cuplike socket of another
Most freely moving
Universal movement allowed
e.g. shoulder & hip joints
