Joints Articulations

1
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

2
Classification of Joints Structural

• Structural classification focuses on the material
  binding bones together and whether or not a joint
  cavity is present
• The three structural classifications are
• Fibrous
• Cartilaginous
• Synovial

3
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, and
  gomphoses

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Fibrous Structural Joints 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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Fibrous Structural Joints Sutures
Figure 8.1a
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Fibrous Structural Joints Syndesmoses

• Bones are connected by a fibrous tissue ligament
• Movement varies from immovable to slightly
  variable
• Examples include the connection between the tibia
  and fibula, and the radius and ulna

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Fibrous Structural Joints Syndesmoses
Figure 8.1b
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Fibrous Structural Joints Gomphoses

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

10
Cartilaginous Joints

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

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Cartilaginous Joints Synchondroses

• A bar or plate of hyaline cartilage unites the
  bones
• All synchondroses are synarthrotic
• Examples include
• Epiphyseal plates of children
• Joint between the costal cartilage of the first
  rib and the sternum

12
Cartilaginous Joints 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
• Examples include intervertebral joints and the
  pubic symphysis of the pelvis

13
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

14
Synovial Joints General Structure

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

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Synovial Joints General Structure
Figure 8.3a, b
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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

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Synovial Joints Friction-Reducing Structures
Figure 8.4
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Synovial Joints Stability

• Stability is determined by
• Articular surfaces shape determines what
  movements are possible
• Ligaments unite bones and prevent excessive or
  undesirable motion

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Synovial Joints Stability

• Muscle tone is accomplished by
• Muscle tendons across joints acting as
  stabilizing factors
• Tendons that are kept tight at all times by
  muscle tone

20
Synovial Joints Movement

• The two muscle attachments across a joint are
• Origin attachment to the immovable bone
• Insertion attachment to the movable bone
• Described as movement along transverse, frontal,
  or sagittal planes

21
Synovial Joints 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

22
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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Angular Movement

• Flexion bending movement that decreases the
  angle of the joint
• Extension reverse of flexion joint angle is
  increased
• Dorsiflexion and plantar flexion up and down
  movement of the foot

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Angular Movement

• Abduction movement away from the midline
• Adduction movement toward the midline
• Circumduction movement describes a cone in space

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Gliding Movement
Figure 8.5a
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Angular Movement
Figure 8.5b
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Angular Movement
Figure 8.5c, d
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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