Joints: Structure and Function Chapter 11

Classification of Joints

Joints, also known as articulations, are points where two or more bones meet. They are classified by both their structure and their function.

• Structural Classification: Based on the material binding the bones and the presence or absence of a joint cavity.

  • Fibrous Joints: Bones joined by dense fibrous connective tissue; no joint cavity.

  • Cartilaginous Joints: Bones joined by cartilage; no joint cavity.

  • Synovial Joints: Bones separated by a fluid-filled joint cavity; most movable type.

• Functional Classification: Based on the amount of movement allowed.

  • Synarthroses: Immovable joints.

  • Amphiarthroses: Slightly movable joints.

  • Diarthroses: Freely movable joints.

Fibrous Joints

Fibrous joints are connected by dense connective tissue and allow little to no movement.

• Sutures: Found between bones of the skull. Example: Coronal suture.

• Syndesmoses: Bones connected by ligaments. Example: Distal tibiofibular joint.

• Gomphoses: Peg-in-socket joints. Example: Teeth in alveolar sockets.

Cartilaginous Joints

Cartilaginous joints unite bones using cartilage and allow more movement than fibrous joints but less than synovial joints.

• Synchondroses: Bones united by hyaline cartilage. Example: Epiphyseal plate in children.

• Symphyses: Bones united by fibrocartilage. Example: Pubic symphysis, intervertebral discs.

Synovial Joints

Synovial joints are the most common and movable type of joint in the body. They have a fluid-filled cavity and several specialized structures.

• Articular Cartilage: Hyaline cartilage covering bone ends.

• Joint (Synovial) Cavity: Space filled with synovial fluid.

• Articular Capsule: Two layers enclosing the joint cavity.

• Synovial Fluid: Lubricates and nourishes the joint.

• Reinforcing Ligaments: Strengthen and support the joint.

• Nerves and Blood Vessels: Provide sensation and nutrients.

Bursae and Tendon Sheaths

Bursae and tendon sheaths are accessory structures that reduce friction in synovial joints.

• Bursae: Flattened sacs containing synovial fluid; reduce friction between tissues.

• Tendon Sheaths: Elongated bursae that wrap around tendons.

Body Movements at Joints

Joints allow various types of movements, classified as angular, rotational, or special movements.

• Flexion/Extension: Decreasing/increasing the angle between bones.

• Abduction/Adduction: Moving limb away/toward the midline.

• Rotation: Turning bone around its axis.

• Special Movements: E.g., pronation, supination, dorsiflexion, plantar flexion.

Types of Synovial Joints

There are six main types of synovial joints, each allowing specific movements.

Arthritis: Types and Comparison

Main Types of Arthritis

Arthritis is inflammation of the joints, leading to pain and stiffness. The three main types discussed are:

• Osteoarthritis: Degenerative joint disease; wear and tear of articular cartilage.

• Rheumatoid Arthritis: Autoimmune disorder; chronic inflammation of synovial membrane.

• Gouty Arthritis: Caused by deposition of uric acid crystals in joints.

Joint Injuries: Strain vs. Dislocation

Comparison of Strain and Dislocation

Joint injuries can be classified based on the nature of the damage.

• Strain: Stretching or tearing of muscle or tendon.

• Dislocation: Displacement of bone from its normal position in the joint.

Additional info: Academic context and examples have been added to expand upon the original question prompts and provide a self-contained study guide.