JOINTS

• Joint


  Point of contact between two bones, between bone and cartilage, or between bone and teeth

  
• Arthrology


  The scientific study of joints
• Kinesiology


  The study of motion of the human body
• Types of joints based on structure

  • Fibrous
  • Cartilaginous
  • Synovial
• Fibrous joints


  • Articulating bones are united by dense irregular connective tissue
  • Degree of movement varies from immovable to slightly movable

  
• Suture


  A fibrous joint composed of a thin layer of dense irregular connective tissue, occurs only between bones of the skull

  
• Sutures are slightly movable in infants and children, but immovable in older individuals</b>
• Synostosis


  A joint in which there is a complete fusion of two separate bones into one
• Syndesmosis


  A fibrous joint with greater distance between articulating surfaces and more dense irregular connective tissue than a suture
• Types of syndesmoses


  • Interosseous ligament
  • Interosseous membrane
  • Gomphosis (between tooth and dental alveolus)
• Cartilaginous joints


  Articulating bones are united by solid piece of hyaline cartilage or fibrous cartilage, range from immovable to slightly movable

  
• Synchondrosis


  Cartilaginous joint with solid piece of cartilage allowing little or no movement, includes epiphyseal cartilage
• Symphysis


  Cartilaginous joint with ends of bones covered in hyaline cartilage and connected by fibrous cartilage disc, slightly movable

  
• Synovial joint


  Characterized by articular capsule surrounding lubricated articular cavity, permits movements ranging from slightly movable to freely movable
• Structures of synovial joints

  • Articular cartilage
  • Articular capsule (fibrous layer and synovial membrane)
  • Articular cavity containing synovial fluid
• Ligaments are bundles of fibrous connective tissue that help hold bones together in synovial joints

  
• "Double-jointed" people have greater flexibility in their articular capsules and ligaments, allowing increased range of motion
• Articular capsule


  Attaches the articulating bones and contains a lubricating fluid
• Synovial joints


  • Presence of an articular cavity permits a wide range of movements from slightly movable to freely movable
  • Surfaces of the bones are covered by a layer of hyaline cartilage called articular cartilage

  
• The distinguishing feature of a synovial joint is the articular cavity between the articulating bones

  
• Synovial fluid


  Viscous, clear or pale yellow fluid that lubricates the joint, absorbs shocks, and supplies oxygen and nutrients to the chondrocytes within articular cartilage
• Functions of synovial fluid

  • Reducing friction by lubricating the joint
  • Absorbing shocks
  • Supplying oxygen and nutrients to and removing carbon dioxide and metabolic wastes from the chondrocytes within articular cartilage
• The popping sound when cracking knuckles results as gases come out of solution to form bubbles in the articular cavity
• Accessory ligaments in synovial joints

  • Extracapsular ligaments (outside the articular capsule)
  • Intracapsular ligaments (within the articular capsule but excluded from the articular cavity)

  
• Articular discs or menisci


  Crescent-shaped pads of fibrous cartilage that lie between the articular surfaces of the bones and are attached to the fibrous capsule

  
• Labrum


  Ring-like fibrous cartilage lip that extends from the circumference of the joint socket
• Synovial joints contain many nerve endings that convey information about pain, movement, and stretch to the spinal cord and brain
• Arteries in the vicinity send out branches that penetrate the ligaments and articular capsule to deliver oxygen and nutrients to the joint tissues
• Bursae


  Saclike structures strategically situated to alleviate friction between moving parts
• Tendon sheaths


  Tube-like bursae that wrap around certain tendons to reduce friction as they pass through tunnels
• Synovial joints


  • Allow gliding movements between nearly flat bone surfaces
  • Allow angular movements with an increase or decrease in the angle between articulating bones
  • Allow rotation of a bone around its own longitudinal axis
  • Allow special movements that occur only at certain joints
• Joints that permit gliding movements

  • Joints between the atlas (the first vertebra) and the occipital bone of the skull
  • Gliding between carpals
• Gliding movements


  Side-to-side and back-and-forth motions
• Bursitis


  Acute or chronic inflammation of a bursa, usually caused by irritation from repeated, excessive exertion of a joint
• Symptoms of bursitis include pain, swelling, tenderness, and limited movement
• Treatment for bursitis may include oral anti-inflammatory agents and injections of cortisol-like steroids