Lecture Notes: Chapter 9 - Articulations

Learning Objectives

• Understand the concept and definition of articulations (joints).
• Identify functional and structural classifications of articulations.

Definition of Articulation

• Articulations = Joints
  • Site where two or more bones interconnect.
  • Includes bones connecting to cartilage and teeth connecting to bone.

Functional Classifications of Joints

1. Synarthrosis (singular) / Synarthroses (plural)

   • Immovable joints.
   • Example: Cranial sutures (coronal, sagittal, squamous, lambdoid).
   • Dense fibrous connective tissue, no movement allowed.

2. Amphiarthrosis / Amphiarthroses

   • Slightly movable joints.
   • Example: Pubic symphysis (cartilage between coxal bones).
   • Allows slight movement to distribute mechanical stress.

3. Diarthrosis / Diarthroses

   • Freely movable joints.
   • Examples: Shoulders, hips, elbows, knees (glenohumeral joint etc.).

Structural Classifications of Joints

1. Fibrous Joints

   • Made of dense connective tissue.
   • Examples:
     • Sutures (synarthrotic, ex. cranial sutures).
     • Syndesmosis (amphiarthrotic, ex. distal tibia and fibula connection via ligament).
     • Gomphosis (synarthrotic, ex. teeth in mandible/maxillae).

2. Bony Joints

   • Originally fibrous or cartilaginous joints that ossify.
   • Example: Metopic suture in the frontal bone.

3. Cartilagenous Joints

   • Bones connected by cartilage.
   • Examples:
     • Synchondrosis (synarthrotic, ex. epiphyseal plates in childhood).
     • Symphysis (amphiarthrotic, ex. pubic symphysis, intervertebral discs).

4. Synovial Joints

   • Encapsulated, contains synovial fluid.
   • Always diarthrotic (freely movable).
   • Provides lubrication, nourishment, and shock absorption.
   • Structure includes:
     • Synovial fluid: lubricates and nourishes.
     • Articular cartilage: caps ends of bones.
     • Joint capsule: fibrous outer layer and synovial membrane inner lining.
     • Accessory structures:
       • Menisci (fiocartilaginous pads, ex. knees).
       • Fat pads (packing material, ex. around joints).
       • Ligaments (bone to bone stabilization).
       • Bursae (fluid-filled sacs reducing friction).
       • Tendons (connect muscle to bone, aid in movement constraints).

Important Notes

• Synovial joint fluid is dynamic and operates to provide lubrication, nutrition, and shock absorption.

• Frequent movement facilitates the health and function of synovial joints.

• Structural differences in joints are related to their functional capabilities.

• Table 9-1 in the textbook provides a cross-reference of functional and structural classifications for deeper study.