classification of joints
DESCRIPTION
CLASSIFICATION OF JOINTSTRANSCRIPT
Joints
Classification of JointsFunctional classification
Synarthroses Amphiarthroses Diarthroses
Synarthroses
• bones are in almost direct contact
• no appreciable motion
• Sutura
• Schindylesis
• Gomphosis
• Synchondrosis
Sutures• margins of the bones are
united by a thin layer of fibrous tissue
• Only between bones of skull
• Fibrous tissue continuous with periosteum
Gomphoses
“peg-in-socket” Insertion of a
conical process into a socket
Only example is tooth with its socket
Schindylesis
• a thin plate of bone is received into a cleft or fissure
• rostrum of the sphenoid• perpendicular plate of the ethmoid with the vomer
Synchondroses• Bones are joined by hyaline cartilage
– rib attachment to sternum by – epiphyseal plate in children binds epiphysis and
diaphysis
Amphiarthroses
• slightly movable articulations• bony surfaces are either connected
by• Symphysis : broad flattened disks of
fibrocartilage, of a more or less complex structure
• Syndesmosis : united by an interosseous ligament
Symphysis
Fibrocartilage unites the bones Slightly movable Resilient shock absorber Provide strength and flexibility
Hyaline cartilage on articular surfaces of bones to reduce friction
Examples Intervertebral discs Pubic symphysis of the pelvis
11
• Two bones bound by ligament– interosseus
membrane
• Interosseus membranes
• unite radius to ulna and tibia to fibula
Syndesmosis
Diarthroses
• bony surfaces are covered with articular cartilage, and connected by ligaments lined by synovial membrane.
• The joint may be divided, completely or incompletely,by an articular disk or meniscus, the periphery of which is continuous with the fibrous capsule
• Eg Synovial joints
Structural classification
• Fibrous• Cartilaginous, • Bony or Synovial
Fibrous joints• Fibrous joints have collagen fibers
spanning the space between bones– sutures– gomphoses – syndesmoses
Cartilagenous joints
Articulating bones united by cartilage Lack a joint cavity Not highly movable Two types
Synchondroses (singular: synchondrosis) Sympheses (singular: symphesis)
Synchondroses
Hyaline cartilage unites the bones Immovable (synarthroses) Examples:
Epiphyseal plates Joint between first rib’s costal cartilage and
manubrium of the sternum
Synchondroses and sympheses
Also pubic symphsis
Synovial joints
Include most of the body’s joints
All are diarthroses (freely movable)
All contain fluid-filled joint cavity
• Uniaxial - all movements take place around one axis
• Biaxial
• polyaxial
Ginglymus(Hinge Joints)
• Articular surfaces are moulded to each other
• Permit motion only in one plane
• Direction which the distal bone takes in this motion is seldom in the same plane as that of the axis of the proximal bone
• Connected together by strong collateral ligaments
• Interphalangeal joints
• Ulna and Humerus at elbow joint
9-20
• One bone has a projection that fits into a ringlike ligament of another
• First bone rotates on its longitudinal axis relative to the other– atlantoaxial joint (dens and atlas)– proximal radioulnar joint allows the radius during
pronation and supination
9-21
Pivot Joints
• Oval convex surface on one bone fits into a similarly shaped depression on the next– radiocarpal joint of the wrist – metacarpophalangeal joints at the bases of
the fingers
• Biaxial joints
9-23
Condyloid (ellipsoid) Joints
Saddle Joints Each articular surface is
shaped like a saddle, concave in one direction and convex in the other◦ trapeziometacarpal joint at
the base of the thumb
Biaxial joint◦ more movable than a
condyloid or hinge joint forming the primate opposable thumb
9-25
• Smooth hemispherical head fits within a cuplike depression– head of humerus into glenoid cavity of
scapula– head of femur into acetabulum of hip bone
• Multiaxial joint
9-26
Ball-and-Socket Joints
Mechanism of lubrication in
synovial joints
Structure
• Hyaline Cartilage
• Ends of long bones (1-5 mm thick)
• Avascular
• Aneural
Composition
Cellular – chondrocytes (10% of volume)
Composition
Extracellular Matrix• Organic – collagen (type II) (10-30% of
weight) & proteoglycans (3-10% of weight)
• Water (most abundant component), inorganic salts, glycoproteins, lipids (60 - 87%)
Composition
• Collagen fibers offer little resistance to compressive forces
• Highly organized stiffness and tensile strength
Composition
• Isotropic – material properties of substance are same regardless of loading
• Hyaline cartilage is anisotropic:• Collagen arrangement • Cross link density• Collagen/PG interaction
Fluid Component
• Permits diffusion of gases, nutrients, wastes SYNOVIAL FLUID
• Important to the structural organization of collagen load bearing /mechanical behavior (80% surface / 65% deep)
Collagen-PG Interaction
• Plays direct role in organization of extracellular matrix
• Important to mechanical properties resists compression
AC under Compression
• constant load rapid initial deformation slow (time dependent) deformation equilibrium
• 20 to exudation of interstitial fluid
Synovial Fluid
• Lubrication
• Reduce Friction
• Nutrition
Synovial Fluid
• Plasma-like
• High in hyaluronate lubrication to reduce friction
• Lubricin – has an affinity for AC - cartilage lubrication
Synovial Fluid
• Hyaluronate (HA) – responsible for viscosity of synovial fluid
• Resistance to shear forces
Type of Lubrication
Boundary – single layer of lubricant molecules on each bearing surface (lubricin has affinity for AC)
Type of Lubrication
Fluid Film • thin fluid film provides greater surface separation • rigid bearings (stainless steel)
Fluid Film Lubrication
• Hydrodynamic – a wedge of fluid is formed when non-parallel surfaces slide over each other
Mixed Lubrication
Mixed Lubrication
Boosted
• ultrafiltration of synovial fluid thru collagen-PG matrix
• H2O & electrolytesarticular cartilage (squeeze-film)
• concentrated gel of HA protein complex coats surfaces (boundary)
Type of Lubrication
Boundary
• high loads
• low relative speeds
• long duration
Fluid-film
• low/oscillated magnitude
• high relative speeds
Synovial joints classified by shape
(of their articular surfaces)
Plane (see right) Hinge (see right) Pivot Condyloid Saddle Ball-and-socket