Joints |

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Jul 15 2010, 4:14 AM EDT (current) AndyC 1 word added, 4 words deleted
Jun 28 2010, 4:08 AM EDT AndyC

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Joints

  • Are places of union between two or more bones.
  • Are innervated as follows: The nerve supplying a joint also supplies the muscles that move the joint and the skin covering the insertion of such muscles (Hilton's law ).muscles.
  • Are classified on the basis of their structural features into fibrous, cartilaginous and synovial types.

Fibrous joints (synarthroses)

  • Are joined by fibrous tissue, have no joint cavities , and permit little movement.
1. Sutures
  • Are connected by fibrous connective tissue (i.e., like uniting a wound with stitches).
  • Are found between the flat bones of the skull.
2. Syndesmoses
  • Are connected by fibrous connective tissue.
  • Occur as the inferior tibiofibular and tympanostapedial syndesmoses.

Cartilaginous joints

  • Are united by cartilage and have no joint cavity.
1. Primary cartilaginous joints (synchondroses)
  • Are united by hyaline cartilage.
  • Permit no movement but growth in the length of the bone.
  • Include epiphyseal cartilage plates (the union between the epiphysis and the diaphysis of a growing bone) and spheno-occipital and manubriosternal synchondroses.
2. Secondary cartilaginous joints (symphyses)
  • Are joined by fibrocartilage and are slightly movable joints.
  • Include the pubic symphysis and the intervertebral disks.

Synovial (diarthrodial) joints

  • Permit a great degree of free movement and are classified according to the shape of the articulation and/or type of movement.
  • Are characterized by four features: joint cavity, articular (hyaline) cartilage,synovial membrane (which produces synovial fluid), and articular capsule.
1. Plane (gliding) joints
  • Are united by two flat articular surfaces and allow a simple gliding or sliding of one bone over the other.
  • Occur in the proximal tibiofibular, intertarsal, intercarpal, intermetacarpal,carpometacarpal, sternoclavicular, and acromioclavicular joints.
2. Hinge (ginglymus) joints
  • Resemble door hinges and allow only flexion and extension.
  • Occur in the elbow, ankle, and interphalangeal joints.
3. Pivot (trochoid) joints
  • Are formed by a central bony pivot turning within a bony ring.
  • Allow only rotation (movement around a single longitudinal axis).
  • Occur in the superior and inferior radioulnar joints and in the atlantoaxial joint.
4. Condylar (ellipsoidal) joints
  • Have two convex condyles articulating with two concave condyles. The shape of the articulation is ellipsoidal.
  • Allow flexion and extension and occur in the wrist (radiocarpal),metacarpophalangeal, knee (tibiofemoral), and atlanto-occipital joints.
5. Saddle (sellar) joints
  • Resemble a saddle on a horse's back and allow flexion and extension, abduction and adduction, and circumduction but no axial rotation.
  • Occur in the carpometacarpal joint of the thumb and between the femur and patella.
6. Ball-and-socket (spheroidal) joints
  • Are formed by the reception of a globular (ball-like) head into a cup-shaped cavity and allow movement in many directions.
  • Allow flexion and extension, abduction and adduction, medial and lateral rotations, and circumduction and occur in the shoulder and hip joints.


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