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Joints

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					 Formed where a bone joins another
  bone, or where a cartilage joins a bone
 The closer the fit, the stronger the joint,
  the more restricted the movement
 The looser the fit, the weaker the joint,
  the greater degree of movement, the
  greater the chance of dislocation
Functions of joints

    Hold bones together

    Allow for mobility
Classification
     FUNCTIONAL
     Classification of Joints!
    3 types of joints if we classify by the
     degree of movement possible:
    1. Diarthroses
          Freely moveable joints
          Shoulder, knee, hip, elbow, interphalangeal, tarsal,
           and carpal joints
    2. Amphiarthroses
          Slightly moveable joints
          Intervertebral discs, costosternal joints, pubic
           symphysis
    3. Synarthroses
          Joints with little or no movement
          Skull sutures, mental symphysis, teeth in sockets,
           1st costosternal joint.
STRUCTURAL Joint
Classification
  Fibrous
  Cartilagenous
  Synovial
Fibrous Joints
   No synovial cavity. Two bones remain held together by thin layer of
    fibrous tissue or dense fibrous tissue or cement or sutures.

    1. Sutures Synostoses – (Suture during infancy but fusion afterwards as
       in Frontal bone). Bones are thin and plate like, held together by inter
       digitations. e.g., skull bones.

    2. Gomphosis One bone remains embedded in the socket of other
       attached through fibres or cement layer. e.g., Thecodont(Greek for "socket-
       tooth ) teeth of humans.


    3. Shindylases One bone fits into slit of other. e.g., ethmoid bone into
       vomer.

    4. Syndesmosis Two bones are united by dense fibrous tissue. e.g., joint
       between skull bones and bones of upper jaw, distal ends of tibia and
       fibula.
Cartilaginous Joints
   No synovial cavity, articulating bones are
    united by cartilage.
    1. Synchondrosis Connecting material is hyaline
       cartilage. e.g., temporary joint between diaphysis
       and epiphysis of a long bone and permanent joint
       between true ribs and sternum.
    2. Symphysis Connecting material is broad flat disc
       of fibrocartilage. e.g., Intervertebral disc and
       symphysis pubis.
 SYNOVIAL
 characterized by:
    articular cartilage - a protective layer of dense white
     connective tissue covering the articulating bone
     surfaces
    articular capsule - a double-layered membrane that
     surrounds the joint
    synovial fluid - a clear, slightly yellow liquid that
     provides lubrication inside the articular capsule
    associated bursae - small capsules filled with synovial
     fluid that cushion the structures they separate
Functions of articular cartilage
 distributing loads over joint surfaces
 improving the fit of articulations
 limiting slip between articulating bones
 protecting the joint periphery
 lubricating the joint
 absorbing shock at the joint
Types of
Synovial Joints
 1.       Plane joints
           Articular surfaces are flat and
            allow short slipping or gliding
            movements.
           Intercarpal and intertarsal
            joints
 2.       Hinge joints
           A cylindrical projection of one
            bone fits into a trough-
            shaped surface on another
            (like a hotdog in a bun)
           Movement resembles a door
            hinge.
           Elbow joint – ulna and
            humerus; Interphalangeal
            joints
Type of
Synovial Joints
3.       Pivot joints
           Rounded end of one bone
            protrudes into a ring formed by
            another bone or by ligaments of
            that bone.
           Proximal radioulnar joint
           Atlas-axial joint
4.       Condyloid joints
           Oval articular surface of one
            bone fits into a complementary
            depression on another.
           Radiocarpal joints
           Metacarpophalangeal joints
Types of
Synovial Joints
5. Saddle joints
     Each articular surface has convex
      and concave areas. Each
      articular surface is saddle-
      shaped.
     Carpometacarpal joints of the
      thumbs.
6. Ball-and-Socket joints
     Spherical or semi-spherical head
      of one bone articulates with the
      cuplike socket of another.
     Allow for much freedom of
      motion.
     Shoulder and hip joints.
Joint Stability
 ability of a joint to resist abnormal
  displacement of the articulating bones
 factors increase joint stability
   a closely reciprocating match of the
    articulating bone surfaces
   a strong array of ligaments and
    muscle tendons crossing the joint
Factors increase joint
stability
    articulating bone surfaces
      wide contact area - high stability
      different among joints and
       individuals
      change in joint angle - change in
       contact area - change in stability
Factors increase joint
stability
  Connective tissues crossing the joint
    weak and lax connective tissues -
     low stability
    strengthening of tissues - increase
     in stability
    muscle activity and fatigue -
     decrease in stability
Joint Flexibility
 a description of the relative ranges of
  motion allowed at a joint in different
  directions
 range of motion (ROM) - the angle
  through which a joint moves from
  anatomical position to the extreme
  limit of segment motion in a particular
  direction
Factors influence joint
flexibility
   Shapes of articulating bone surfaces
   Intervening muscle or fatty tissue
   Laxity
   Extensibility of collagenous tissue
    and muscles
   Fluid contents in cartilagenous disc
   Temperature of collageneous tissues
   Stretching program
Joints (Types of Movements
at Synovial Joints)
     Specific terminology is used to designate the
      movements that occur at joints
     Movements are grouped into four main
      categories:
     1.   Gliding
     2.   Angular movements
     3.   Rotation
     4.   Special movements
 Gliding:
   Simple movement back-and-forth and from
    side-to-side
   There is no significant alteration of the angle
    between the bones
   Limited in range
 Eg., Intercarpal joints
 Angular Movements:
   Increase or a decrease in the angle between
    articulating bones
 Types:
     Flexion
     Extension
     Lateral flexion
     Hyperextension
     Abduction
     Adduction
 Circumduction:
   Movement of a body part in a circle
   Moving the humerus in a circle at the
    shoulder joint
 Rotation:
   A bone revolves around its own longitudinal
    axis
   Turning the head from side to side as when
    you shake your head “no”
 Special Movements
     Elevation
     Depression
     Protraction
     Retraction
     Inversion
     Eversion
     Dorsiflexion
     Plantar flexion
     Supination
     Pronation
     Opposition

				
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posted:11/23/2010
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