Introduction Joints, or articulations, are connections between bones that may or may not permit movement
Joints, or articulations, are connections between bones that may or may not permit movement.
Cartilage, fluid, or dense connective tissues are usually involved in holding joints together.
Joints are classified functionally by the amount of movement they allow.
Immovable or slightly movable joints tend to be in the axial skeleton.
Freely movable joints are more common in the appendicular skeleton.
Classification of Joints
Synarthroses (Immovable Joints)
Sutures are joints found only in the skull.
Bony edges interlock and short dense connective tissue fiber holds the bones together.
A gomphosis is the joint between a tooth and the alveolar fossa of the maxillae or mandible.
Periodontal ligaments hold the tooth to the bone in the gomphosis.
A synchondrosis is a joint in which hyaline cartilage separates the ends of the bones involved in the joint.
A synostosis occurs if bones fuse together to form one bone.
Amphiarthroses (Slightly Movable Joints)
A syndesmosis occurs when bones are connected by relatively long connective tissue ligaments.
Connecting bones using a fibrocartilage pad forms a symphysis.
Diarthroses (Freely Movable Joints)
Synovial joints are typically found at the ends of long bones in the upper and lower limbs.
All synovial joints have 6 basic characteristics:
A joint capsule
A joint cavity filled with synovial fluid
A synovial membrane lining the joint capsule
Sensory nerves and blood vessels
Synovial fluid has three functions:
Nourishes the chondrocytes by entering and exiting the articular cartilages due to the forces acting on the joint
Articular Form and Function
Movements at the ankle include
Movement of the pollex (thumb)
Special movements that occur at many joints include:
Protraction is movement anteriorly in the horizontal plane.
Retraction is movement posteriorly in the horizontal plane.
Elevation is movement cranially in the vertical axis.
Depression is movement caudally in the vertical axis.
A Structural Classification of Joints
A Structural Classification of Joints (cont.)
Flexion/extension and abduction/adduction
Biaxial joints that also allow circumduction
There are four possible movements of the vertebral column:
Extension, or bending backward
Rotation, or twisting
Aging and Articulations
Bones and Muscles
Skeletal and muscular systems are structurally and functionally interdependent.
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