Articulations - Chapter Nine

Overview

• Articulations refer to joints.
• Joints do not always involve movement; some may be immobile.
• Different types of cartilage are present in joints, including hyaline, fibrocartilage, and elastic cartilage.

Types of Cartilage

• Hyaline Cartilage: Found at the ends of bones, prevents friction. Present in most joints.
• Fibrocartilage: Strong, found between vertebrae and pubic bones.
• Elastic Cartilage: Provides flexibility, found in the ears.

Joint Classifications

• Structural Classification:
  • Fibrous Joints: Dense regular connective tissue; no joint cavity.
    • Examples: Gomphoses (teeth), Sutures (skull), Syndesmoses (between parallel bones like radius and ulna).
  • Cartilaginous Joints: Made of cartilage; no joint cavity.
    • Examples: Synchondrosis (hyaline cartilage, e.g., epiphyseal plates), Symphyses (fibrocartilage, e.g., pubic symphysis).
  • Synovial Joints: Have a synovial capsule with fluid; allow for movement (diarthroses).

Functional Classification

• Synarthroses: Immobile joints (e.g., sutures, gomphoses).
• Amphiarthroses: Slightly mobile joints (e.g., syndesmoses, symphyses).
• Diarthroses: Freely mobile joints (e.g., synovial joints).

Synovial Joint Components

• Articular Capsule: Protects the joint, consists of a fibrous layer and a synovial membrane.
• Synovial Fluid: Provides lubrication, nutrients to cartilage, and shock absorption.
• Articular Cartilage: Made of hyaline cartilage, prevents friction between bones.
• Ligaments: Strengthen and reinforce the joint.

Synovial Joint Types

1. Plane Joints: Allow gliding movements, uniaxial.
2. Hinge Joints: Allow flexion and extension, uniaxial (e.g., elbow, knee).
3. Pivot Joints: Allow rotational movement, uniaxial (e.g., C1 and C2 vertebrae).
4. Condylar Joints: Allow movement in two axes, biaxial (e.g., fingers).
5. Saddle Joints: Biaxial, allow more range than condylar (e.g., thumb).
6. Ball and Socket Joints: Allow multi-directional movement, multi-axial (e.g., shoulder, hip).

Joint Movement Types

• Gliding: Simple sliding motion (e.g., intercarpal joints).
• Angular: Changes angle between bones; includes flexion, extension, abduction, adduction.
• Rotational: Movement around an axis; includes medial/lateral rotation.
• Special Movements: Include elevation, depression, dorsiflexion, plantarflexion, inversion, eversion, protraction, retraction, opposition.

Important Concepts

• Inverse Relationship: More mobility results in less stability and vice versa.
• Nutrient Supply: Synovial fluid provides nutrients to cartilage, which is avascular.
• Synovial Joint Vulnerability: More movement potential often means higher risk of injury (e.g., shoulder dislocation).

Additional Information

• Specific examples and identification of joints will be covered further in lab sessions.

Note

• Reach out if you have any questions or need further clarification on articulations or joints.