Articular System - Classification of Joints

Articular System - Classification of Joints

• Joints: Articulations where two or more bones meet, joined by soft tissue. They allow movement, provide shock absorption, and maintain stability. Balance between mobility and stability is crucial.

• Joint Functions:

  • Movement: Muscle action allows joint movement.
  • Shock Absorption: Cartilage, menisci, and synovial fluid cushion the joint.
  • Stability: Ligaments, joint capsules, and other structures stabilize the joint.

Structural Classification of Joints

• Fibrous Joints: Connected by dense fibrous connective tissue. They allow little to no movement.

  • Types:
    • Sutures (skull): Allow for cranial bone movement during birth.
    • Gomphoses (teeth): Connect teeth to the jawbone.
    • Syndesmoses: Connect bones with ligaments (e.g., distal and proximal radioulnar joints).

• Cartilaginous Joints: Connected by cartilage. They allow limited movement.

  • Types:
    • Symphyses: Connected by a fibrocartilaginous disc (e.g., pubic symphysis, intervertebral discs).
    • Synchondroses: Connected by hyaline cartilage (e.g., sternocostal joints).

• Synovial Joints: Contain a joint cavity. They allow significant movement.

Functional Classification of Joints

• Synarthroses: Allow little to no movement (e.g., fibrous joints).
• Amphiarthroses: Allow moderate movement (e.g., cartilaginous joints).
• Diarthroses: Allow significant movement (e.g., synovial joints).

Synovial Joint Components

• Joint Capsule: Outer fibrous layer, inner synovial membrane, encloses the joint.
• Synovial Membrane: Produces synovial fluid, a lubricant.
• Synovial Fluid: Reduces friction between joint surfaces, provides nutrients.
• Hyaline Cartilage: Covers articular surfaces of bones, smooths movement.
• Ligaments: Fibrous structures that run between bones (extra-articular or intra-articular).

Classification of Synovial Joints (based on degrees of freedom in movement):

• Uniaxial Joints: Movement in one plane around one axis.

  • Hinge Joints: Elbow, knee, ankle (one surface is spool-like, the other concave).
  • Pivot Joints: Atlantoaxial joint, superior radioulnar joint (one surface is ring-shaped).

• Biaxial Joints: Movement in two planes around two axes.

  • Condyloid/Ellipsoid Joints: Radiocarpal joint, MCPs of hand (one bone concave, the other convex).
  • Saddle Joints: CMC of thumb, sternoclavicular joint (both bones have convex and concave parts).

• Triaxial Joints: Movement in three planes around three axes.

  • Ball and Socket Joints: Glenohumeral joint, hip (ball-shaped surface fitting into a socket).

• Nonaxial/Plane Joints: Gliding motion occurs, no movement around an axis; e.g., intercarpal joints and facet joints.

This quiz explores the articular system and its classification of joints. Discover the different types of joints, their functions, and how they are structurally classified. Test your understanding of fibrous and cartilaginous joints and their significance in movement and stability.