Unit 3: The Skeletal System - Joints

Introduction

• Focus on joints, also known as articulations.
• Joints: where two bones meet, providing flexibility but are weak points.
• Classify joints by:
  • Structure
  • Function
• Class handout: sketch a typical synovial joint.
• D2L handout with relevant lab manual pages.

Joints Overview

• Articulations: Sites where bones meet.
• Importance: Provide flexibility to the skeleton.
• Joints are weak points in the bone structure.
• Ligaments: Bone-to-bone connections.
• Tendons: Bone-to-muscle connections.

Joint Classification

• Functional Classification:

  • Synarthroses: Immovable joints (e.g., tooth socket).
  • Amphiarthroses: Slightly movable joints (e.g., pelvic joint).
  • Diarthroses (Synovial joints): Freely movable joints (e.g., wrist).

• Structural Classification:

  • Binding materials:
    • Fibrous Joints: Held by fibers.
    • Cartilaginous Joints: Held by cartilage.
    • Synovial Joints: Held by a synovial membrane with fluid.

Fibrous Joints

• Characteristics: Dense fibrous connective tissue, no joint cavity.
• Types:
  • Sutures (e.g., skull)
  • Syndesmoses (e.g., ankle)
  • Gomphoses (e.g., tooth sockets)

Cartilaginous Joints

• Types:
  • Synchondrosis: Immovable, held by hyaline cartilage (e.g., epiphyseal plate).
  • Symphyses: Slightly movable, held by fibrocartilage (e.g., pubic symphysis).

Synovial Joints

• Characteristics: Synovial membrane, joint cavity with synovial fluid.
• Reducing friction:
  • Bursa: Small fluid-filled sacs.
  • Tendon Sheath: Wraps around tendons.

Movements of Synovial Joints

• Gliding Movements: Flat bones gliding (e.g., wrist).

• Angular Movements:

  • Flexion: Reducing the angle (e.g., knee).
  • Extension: Increasing the angle.
  • Abduction/Adduction: Moving away/towards midline.
  • Circumduction: Circular motion.
  • Rotation: Turning around an axis.

• Special Movements:

  • Supination/Pronation: Palm orientation.
  • Dorsiflexion/Plantar Flexion: Foot movements.
  • Inversion/Eversion: Ankle movements.
  • Protraction/Retraction: Movements of the jaw.
  • Elevation/Depression: Raising or lowering (e.g., shoulders).
  • Opposition: Thumb movement.

Types of Synovial Joints

• Plane Joints: Flat surfaces gliding.
• Hinge Joints: Movement in one plane (e.g., elbow).
• Pivot Joints: Rounded end fits into a ring.
• Condyloid Joints: Oval surfaces for angular movements.
• Saddle Joints: Greater freedom (e.g., thumb).
• Ball and Socket Joints: Most freely moving (e.g., shoulder, hip).

Joint Injuries and Disorders

• Sprains: Stretched or torn ligaments.
• Cartilage Damage: Slow to repair, often needs surgery.
• Dislocations: Common in freely moving joints.
• Arthritis: Inflammatory/degenerative diseases.
  • Osteoarthritis: Wear and tear.
  • Rheumatoid Arthritis: Autoimmune disease.

Conclusion

• Review class handouts and slides for upcoming exams.
• Lab handouts focus on muscles, not joints.