Muscular System: Structural Classification of Articulations

MUSCULAR SYSTEM: STRUCTURAL CLASSIFICATION OF ARTICULATIONS

Articulations and the Muscular System

  • The skeletal and muscular systems work together to create movement at the points where bones meet.

  • Articulations: Points where bones come together (commonly referred to as joints).

  • Types of articulations include:

  • Fused Joints: No movement occurs.

  • Movable Joints: Allow varying degrees of movement.

  • Synovial Joints: Muscles span the space where the bones meet, allowing significant movement.

Classification of Articulations

  • Structural Classification: Based on type of connective tissue that binds the bones.

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

  • Types of Joints:

    • Fibrous: (Immovable)

    • Cartilaginous: (Slightly movable)

    • Synovial: (Freely movable)

Joint Vocabulary

  • Articulation: Where bones come together (joint).

  • Arthro: Joint.

  • Amphi: On both sides.

  • Bursa: Like a purse or pillow, helps reduce friction.

  • Chondro: Relating to cartilage.

  • Desmo: Relating to ligaments.

  • Dia: Through, apart.

  • Gompho: Peg in socket joints.

  • Syn: Together.

Functions of Joints

  • Where: Two or more bones meet (joints).

  • Functions:

  • Bind parts of the skeletal system together.

  • Allow immovable joints.

  • Permit slight movement.

  • Enable body parts to move in response to muscle contractions.

  • Provide a wide range of motion.

Joint Classification by Function or Tissue Type

  • Functional Classifications:

  • Synarthroses: Immoveable joints.

  • Amphiarthroses: Slightly movable joints.

  • Diarthroses: Freely movable joints.

  • Structural Classifications:

  • Fibrous Joints: Held by dense connective tissue; immovable.

  • Cartilaginous Joints: Joint made of cartilage; slightly movable to immovable.

  • Synovial Joints: Freely movable joints with a fluid-filled cavity.

Structural Joints: Types

1. Fibrous Joints

  • Description: Bones connected by dense regular connective tissue (ligaments).

  • Types:

  • Sutures: Immovable joints found only in the skull.

  • Syndesmoses: Joints between distal tibia/fibula or radius/ulna; slightly movable.

  • Gomphoses: Peg-in-socket joint, such as teeth in their sockets.

2. Cartilaginous Joints

  • Description: Bones connected by cartilage; no joint cavity.

  • Types:

  • Synchondroses: Composed of hyaline cartilage; found in epiphyseal plates.

  • Symphyses: Composed of fibrocartilage; examples include intervertebral joints and pubic symphysis.

3. Synovial Joints

  • Characteristics:

  • Predominantly found in the appendicular skeleton.

  • Bones are separated by a fluid-filled cavity, allowing for free movement.

  • Contains rich nerves and blood vessels.

  • Six subtypes to be discussed further.

Key Characteristics of Synovial Joints

  1. Articular Cartilage: Hyaline cartilage covering bone ends for cushioning.

  2. Joint Cavity: Space filled with synovial fluid between the bones.

  3. Joint Capsule: Dense irregular connective tissue that strengthens the joint.

  4. Synovial Fluid: Viscous fluid reducing friction and providing nutrients to cartilage.

  5. Reinforcing Ligaments: Fibrous cords that hold bones together.

  6. Blood Supply & Nerves: Providing sensation and nutrition.

Additional Structures in Synovial Joints

  • Meniscus: Fibrocartilage pad that absorbs shock and provides cushioning (e.g., knee joint).

  • Labrum: Fibrocartilage structure in shoulder and hip joints that provides stability.

  • Bursae: Pillow-like structures filled with synovial fluid that cushion joint movement.

  • Tendon Sheath: Elongated structure around tendons, reducing friction during movement.

Factors Influencing Stability of Synovial Joints

  • Muscle Tone: Most important factor; keeps tendons taut, reinforcing stability.

  • Shape of Articular Surface: Shallow surfaces like in shoulder joints are less stable than deeper joints like hips.

  • Ligament Count and Location: More ligaments generally lead to stronger, more stable joints.