Joints

1
Joints

• Articulating your body

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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

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Classification of Joints Structural

• Structural classification
• focuses on the material between bones
• Whether or not a joint cavity is present
• The three structural classifications are
• Fibrous
• Cartilaginous
• Synovial

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Classification of Joints Functional

• Functional classification is based on the amount
  of movement allowed by the joint
• The three functional classes of joints are
• Synarthroses immovable
• Amphiarthroses slightly movable
• Diarthroses freely movable

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Fibrous Structural Joints

• The bones are joined by fibrous tissues
• There is no joint cavity
• Most are immovable
• There are three types
• Sutures
• Syndesmoses
• gomphoses

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Sutures
Figure 8.1a
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Sutures

• Occur between the bones of the skull
• Comprised of interlocking junctions completely
  filled with connective tissue fibers
• Bind bones tightly together, but allow for growth
  during youth
• In middle age, skull bones fuse and are called
  synostoses

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Syndesmoses
Figure 8.1b
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Syndesmoses

• Bones are connected by a fibrous tissue ligament
• Movement varies from immovable to slightly
  variable

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Gomphoses

• The peg-in-socket fibrous joint between a tooth
  and its alveolar socket
• The fibrous connection is the periodontal ligament

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Cartilaginous Joints

• Articulating bones are united by cartilage
• Lack a joint cavity
• Two types synchondroses and symphyses

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Synchondroses
Figure 8.2a, b
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Synchondroses

• A bar or plate of hyaline cartilage unites the
  bones
• All synchondroses are synarthrotic

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Symphyses
Figure 8.2c
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Symphyses

• Hyaline cartilage covers the articulating surface
  of the bone and is fused to an intervening pad of
  fibrocartilage
• Amphiarthrotic joints designed for strength and
  flexibility

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Synovial Joints

• Those joints in which the articulating bones are
  separated by a fluid-containing joint cavity
• All are freely movable diarthroses
• Examples all limb joints, and most joints of
  the body

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General Structure

• Synovial joints all have the following
• Articular cartilage
• Joint (synovial) cavity
• Articular capsule
• Synovial fluid
• Reinforcing ligaments

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General Structure
Figure 8.3a, b
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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

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Friction-Reducing Structures
Figure 8.4
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Range of Motion

• Nonaxial slipping movements only
• Uniaxial movement in one plane
• Biaxial movement in two planes
• Multiaxial movement in or around all three
  planes

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Stability

• Determined by
• Articular surfaces
• shape determines what movements are possible
• Ligaments
• unite bones and prevent excessive or undesirable
  motion
• Muscle tone is accomplished by
• Muscle tendons across joints acting as
  stabilizing factors
• Tendons that are kept tight at all times by
  muscle tone

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Range of Motion

• Nonaxial
• slipping movements only
• Uniaxial
• movement in one plane
• Biaxial
• movement in two planes
• Multiaxial
• movement in or around all three planes

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Gliding Movements

• One flat bone surface glides or slips over
  another similar surface
• Examples intercarpal and intertarsal joints,
  and between the flat articular processes of the
  vertebrae

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Gliding Movement
Figure 8.5a
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Angular Movement

• Flexion
• bending movement that decreases the angle of the
  joint
• Extension
• reverse of flexion joint angle is increased

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Angular Movement
Figure 8.5b
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Knee
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Angular Movement
Figure 8.5c, d
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Angular Movement

• Dorsiflexion and plantar flexion
• up and down movement of the foot
• Abduction
• movement away from the midline
• Adduction
• movement toward the midline
• Circumduction
• movement describes a cone in space

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Angular Movement
Figure 8.5e, f
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Rotation

• The turning of a bone around its own long axis
• Examples
• Between first two vertebrae
• Hip and shoulder joints

Figure 8.5g
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Special Movements

• Supination and pronation
• Inversion and eversion
• Protraction and retraction
• Elevation and depression
• Opposition

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Special Movements
Figure 8.6a
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Special Movements
Figure 8.6b
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Special Movements
Figure 8.6c
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Special Movements
Figure 8.6d
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Special Movements
Figure 8.6e