Synovial Joints Overview

Synovial Diarthroses

• Uniaxial: Movement in one plane (flexion and extension)
  • Example: humero-cubital joint (knee)
• Biaxial: Movement in two planes (flexion, extension, and rotation)
  • Example: radio-humeral joint (elbow)
• Multiaxial: Movement in three planes (circumduction)
  • Example: glenohumeral joint (shoulder)

Synovial Joints by Shape

• Planar (Arthrodial): Two flat surfaces; sliding movement
  • Examples: acromioclavicular joint (clavicle and shoulder blade) or carpals.
• Ginglymus (or Hinge): A hinge-like structure, allowing movement in one plane (flexion-extension).
  • Example: humerocubital joint (elbow).
• Trochoid (or Pivot): One axis, the end of one bone moves through the diaphysis of another, enabling rotation.
  • Example: articulation between atlas and axis, or radius and ulna (rotation of one over the other.
• Elliptical (Condyloid): Two perpendicular axes, allowing movement of flexion, extension, abducting, and adducting, and slight circular movement.
  • Example: wrist.
• Condyloid (Elliptical): 2 axes; Allows flexion, extension, abduction, adduction.
  • Example: Wrist.
• Bicondylar: One axis allowing mainly flexion and extension with limited rotation.
  • Example: Knee.
• Saddle (sellar): Two surfaces fit together like a saddle. Allows movements in two perpendicular axes (flexion, extension, abduction, adduction, and rotation).
  • Example: carpometacarpal joint of the thumb.
• Spheric/Ball-and-socket (Enarthrosis): A ball and socket; Allows 3 axes of movement (flexion, extension, abduction, adduction, and rotation)
  • Example: Shoulder, hip

Fibrous/Immovable Joints (Synarthroses)

• Fibrous joints: No joint cavity; held together by fibrous connective tissue or cartilage. Limited mobility.
  • Examples: sutures (skull), gomphoses (teeth), syndesmoses (vertebral lamina).

Cartilaginous or Amphiarthrotic Joints

• Cartilaginous joints: Have cartilage that eventually disappears.
• Synchondrosis: a layer of growth cartilage...synostosis is the complete ossification of the metaphysis (rib and sternum). The rib joint persists in the adult.
• Symphysis: two separated bones are interconnected by cartilage (which allows some movement): diarthranfiarthrosis

Amphiarthrosis

• Semi-mobile.

Skin

• The largest organ of the body.
• Functions:
  • Permeable mechanical barrier
  • Primary immune organ.
• Originates from the ectoderm.