Nerve activates contraction by HC12091021443


									Joints (Articulations)

                          Weakest parts of the skeleton
                          Articulation – site where two
                           or more bones meet
                          Functions of joints
                              Give the skeleton mobility
                              Hold the skeleton together
                          Classified by Function and
Functional Classification of Joints:
  Based on amount of movement allowed
  3 functional classes:
      Synarthroses – immovable
      Amphiarthroses – slightly movable
      Diarthroses – freely movable
Structural Classification of Joints
  Classification by material binding bones together and
   whether or not a joint cavity is present
  The three structural classifications are:              Each structural
     Fibrous joints – fibers connect bones               class has
     Cartilaginous joints – cartilage connections
     Synovial joints – bones articulate inside cavity (freely
      moveable, i.e. all are diarthroses)
Fibrous Joints – no joint cavity, usually synarthrotic (3 types)
 Sutures – interlocking junctions
  between skull bones
     Bind bones, but allow growth
      (fuse with osseous tissue in
      middle age = synostoses)
 Syndesmoses – bones
  connected by fibrous ligament
     Some = amphiarthrotic
     Ex. Tibia-Fibula, Radius-Ulna
 Gomphoses – peg-in-socket joint
  of teeth in alveolar socket
     Periodontal ligament
Cartilaginous Joints also lack joint cavity (2 types)
  Synchondroses – bar or
   plate of hyaline cartilage
      All synarthrotic
      Epiphyseal plates and
       first rib to sternum
  Symphyses – hyaline
   cartilage on articulating
   bones fused by
      Amphiarthrotic
      Intervertebral discs,
       pubic symphisis
Synovial Joints have a joint cavity
  All are freely movable diarthroses
  Examples – all limb joints, and most joints of the body
Synovial Joints: General Structure
 Synovial joints all have the following
     Articular cartilage – hyaline
      covers ends of bones
     Articular capsule – dense
      fibrous outer layer w/ inner
      synovial membrane (makes
      hyaluronic acid rich fluid)
     Joint (synovial) cavity
     Synovial fluid – lubricates,
      nourishes cartilage, contains
     Reinforcing ligaments – often        Also contain rich supply of
      part of fibrous capsule              blood vessels and nerves
Table 8.2.1
Table 8.2.2
Table 8.2.3
Synovial Joints: Friction-Reducing Structures
  Bursae – flattened, fibrous sacs lined with synovial membranes and
   containing synovial fluid
  Common where ligaments, muscles, skin, tendons, or bones rub together
  Tendon sheath – elongated bursa that wraps completely around a tendon
Synovial Joints: Stability
     What keeps these constantly stretched,
     compressed, twisted connections together?

 Articular surfaces – shape determines
  movements, some = snug, stable fit
 Ligaments – unite bones, prevent
  excessive motion
 Muscle tone – keeps tendons that
  cross joints taught = joint stability (usu.
  most important stabilizer)
  Movement by synovial joints determined by muscles
 Muscles attach to at least
  two points
    Origin - Attachment to
     immoveable bone
    Insertion - Attachment to
     movable bone

  Movements are described in
   relation to transverse, frontal,
   or sagittal planes

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