Articulations and Joint Classifications

Articulations Overview

• Articulation is where two or more bones, or a bone and cartilage, connect.
• Various joint types are classified based on structure and function, influencing mobility.

Joint Classifications

• Synovial Cavity: Contains synovial fluid, providing lubrication between articulating bones.
• Fibrous Joint: No synovial cavity; bones connected by fibrous connective tissue.
• Cartilaginous Joint: No synovial cavity; bones connected by cartilage.
• Synovial Joint: Contains a synovial cavity; articulating bones are united by an articular capsule.

Functional Classifications

• Synarthrosis: Immovable joints.
• Amphiarthrosis: Semi-movable joints.
• Diarthrosis: Freely movable joints, encompassing all synovial joints.

Joint Types and Examples

• Suture: Synarthrosis joint in the skull.
• Gomphosis: Synarthrosis joint between teeth and jawbone.
• Synchondrosis: Synarthrosis joint with hyaline cartilage (e.g., growth plates).
• Syndesmosis: Amphiarthrosis joint with fibrous tissue.
• Symphysis: Amphiarthrosis joint with broad fibrocartilage.

Joint Structures

• Articular Cartilage: Hyaline cartilage covering the ends of bones within a joint.
• Articular Capsule: Envelops the joint and synovial cavity, connecting bones.
• Fibrous Capsule: Outer layer of the articular capsule, made of dense irregular connective tissue.
• Synovial Membrane: Inner layer of the articular capsule secreting synovial fluid.
• Synovial Fluid: Lubricates joints and provides nutrients.
• Bursae: Shock-absorbing sacs within joints, reducing friction.

Joint Movement Types

• Gliding Joint: Flat surfaces enabling back and forth, side to side movement (e.g., carpals and tarsals).
• Hinge Joint: Convex surface fitting into a concave counterpart for flexion and extension (e.g., elbow, knee).
• Pivot Joint: Rounded surface connects with a ring for rotational movement (e.g., atlas and axis of the neck).
• Condyloid Joint: Oval-shaped surface fitting into a depression allowing movement in two planes (e.g., radius with scaphoid).
• Saddle Joint: One bone is shaped like a saddle; allows side-to-side and back-and-forth movement (e.g., trapezium with the first metacarpal).
• Ball & Socket Joint: Ball-shaped surface fits into a cup-shaped depression, allowing for multi-directional movement (e.g., shoulder, hip).