Introduction to Joints

Introduction to Joints

• Joints are where two or more bones meet in the skeletal system.
• Joints allow movement and provide stability.
• Arthrology is the science that studies joints.

Classifications of Joints

• Functional Classification: Categorizes joints by the amount of movement they allow.
  • Immovable (Synarthroses): No movement.
  • Slightly Movable (Amphiarthroses): Limited movement.
  • Freely Movable (Diarthroses): Wide range of motion.
• Structural Classification: Categorizes joints based on the material that binds them together.
  • Fibrous Joints: Immovable, connected by fibrous connective tissue.
  • Cartilaginous Joints: Slightly movable, connected by cartilage.
  • Synovial Joints: Freely movable, with a joint cavity filled with synovial fluid.

Fibrous Joints

• Synarthroses and Synostoses: Immovable joints.
  • Examples: Skull bones, pelvic bones.
• Types:
  • Sutures: Found in the skull, between skull bones, fuse together in middle age.
  • Gomphoses: Specialized joint between teeth and their sockets (periodontal ligament).
  • Syndesmoses: Bones connected by short ligaments, allowing slight movement.
    • Example: Radius and ulna, tibia and fibula.
• Bony Joints (Synostoses): Formerly separate bones that have fused together.
  • Example: Frontal bone, epiphyseal line.

Cartilaginous Joints

• Amphiarthroses: Slightly movable, connected by cartilage.
• Types:
  • Synchondroses: Hyaline cartilage connects bones.
    • Examples: Epiphyseal plate, costal cartilage (connecting ribs to sternum).
  • Symphyses: Fibrocartilage connects bones.
    • Examples: Pubic symphysis, intervertebral joints.

Synovial Joints

• Diarthroses: Freely movable joints.
  • Joint Cavity: Space between bones filled with synovial fluid.
• Components:
  • Articular Capsule: Encloses the joint cavity.
    • Outer Fibrous Capsule: Continuous with periosteum, provides strength and stability.
    • Inner Synovial Membrane: Produces synovial fluid for lubrication and nourishment.
  • Meniscus: Cartilage pad within the joint, acts as a shock absorber.
  • Tendon: Connects muscle to bone.
  • Ligament: Connects bone to bone.

Types of Synovial Joints

• Based on Axes of Movement:
  • Nonaxial: No movement.
  • Uniaxial: Movement in one plane.
  • Biaxial: Movement in two planes.
  • Multiaxial: Movement in three planes.
• Based on Shape:
  • Hinge Joint: Uniaxial, allows flexion and extension.
    • Examples: Elbow, knee, finger/toe joints.
  • Ball-and-Socket Joint: Multiaxial, allows movement in all directions.
    • Examples: Shoulder, hip joints.
  • Pivot Joint: Uniaxial, allows rotation around a central axis.
    • Examples: Atlas-axis (neck), radioulnar (forearm).
  • Saddle Joint: Biaxial, allows movement in two planes (flexion/extension and abduction/adduction).
    • Example: Base of the thumb joint (1st carpometacarpal joint).
  • Condyloid Joint: Biaxial, modified ball and socket.
    • Examples: Metacarpophalangeal joints (base of fingers).
  • Ellipsoid Joint: Biaxial, allows flexion, extension, abduction, adduction.
    • Example: Radiocarpal joint (wrist).
  • Compound Joint: Possesses two or more types of joints.
    • Example: Temporomandibular joint (TMJ) which is a combination of hinge and gliding.

Summary Table

Explore the essential concepts related to joints in the skeletal system. This quiz covers the classifications of joints, their functions, and detailed descriptions of fibrous joints. Test your understanding of arthrology and the significance of various joint types for movement and stability.