Joints

• Joints


  Permit mobility but not all junctions between bones are designed to allow movement
• Cranial sutures in adults

  • Rigidly fixed
• Shoulder joint


  • Has an almost unlimited range of movement
• Tibiofibular joint


  • Limited movement but firmly bound by fibrous and cartilaginous tissue
• Synovial joints


  Articulating surfaces are in contact but not in continuity
• Articular surfaces of synovial joints

  • Covered by a thin layer of hyaline or, occasionally, fibrous cartilage, up to 3mm thick
• Synovial fluid


  Viscous, clear fluid that lubricates the joint surfaces and supplies essential nutrients to the chrondocytes of the articular cartilage
• Synovial joints


  • Enclosed by a tough fibrous capsule, which in turn is lined by a thin synovial membrane
• Ligaments


  Band-like thickenings of the joint capsule which not only provide stability but as with the cruciate ligaments of the knee joint, limit excessive mobility
• Tendons, ligaments and joint capsules


  Insert into bone, their collagen fibres becoming incorporated into the underlying bone
• Knee and sternoclavicular joints

  • Have partial or complete discs of fibrocartilage called menisci, which either project into the joint cavities or divide them into separate cavities. These may act as "cushions" or "shock absorbers"
• Substantial pathological process involving a joint

  Likely to cause inflammatory cell infiltration, oedema of the adjacent joint capsule, and if not, the articular surfaces themselves, leading to pain and subsequent limitation of movement
• Ligaments

  Composed of:

  Dense fibrous bundles of collagenous fibres

  Spindle shaped cells - fibrocytes

  Little ground substance (del-like component of various connective tissue)

  2 types:

  • White ligaments
  • Rich in collagenous fibres
  • Sturdy and inelastic
  • Yellow ligaments (most common in joints)
  • Rich in elastic fibres
  • Tough even though they allow elastic movement

  Ligaments attach bone to bone
• Tendons

  Tough, flexible straps or cords which connect muscles to bone.

  Composed of:

  -compact linear collagen fibres with compressed nuclei of inactive fibroblasts between the collagen bundles

  Poorly vascularised so heal slowly when damaged.

  Some have a thin outer layer of synovium
• Cartilage -> A firm tissue but softer and more flexible than bone.

  • Joints between bones
  • Ends of ribs
  • Between vertebrae
  • In the spine, ears, nose
  • Bronchial tubes and airways

  Made up of chondrocytes. Produce large amounts of extracellular matrix composed of:

  • Collagen fibres
  • Proteoglycan
  • Elastin fibres

  No blood vessels in cartilage to supply the chondrocytes with nutrients.

  Instead, nutrients diffuse through dense CT surrounding cartilage (perichondrium) and into the core of the cartilage. Due to lack of blood vessels, cartilage grows and repairs a lot slower.