Articulations

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Articulations
Chapter 8
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Joints (Articulations)

• Weakest parts of the skeleton
• Articulation
• Functions of joints
• Give the skeleton mobility
• Hold the skeleton together

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Structural Classification of Joints

• The three structural classifications are
• 1. Fibrous
• 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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Structural Classification of Joints

• The three structural classifications are
• 1. Fibrous (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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Structural Classification of Joints

• The three structural classifications are
• Fibrous

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Structural Classification of Joints

• The three structural classifications are
• 1. Fibrous (Syndemosis)

• 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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Structural Classification of Joints

• The three structural classifications are
• 1. Fibrous (Syndemosis)

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Structural Classification of Joints

• The three structural classifications are
• 1. Fibrous (Gomphosis)

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

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Structural Classification of Joints

• The three structural classifications are
• Cartilaginous
• Articulating bones are united by cartilage
• Lack a joint cavity
• Two types synchondroses and symphyses

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Structural Classification of Joints

• The three structural classifications are
• Cartilaginous (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

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Structural Classification of Joints

• The three structural classifications are
• Cartilaginous (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

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Structural Classification of Joints

• The three structural classifications are
• Synovial
• 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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Structure of Synovial Joints

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

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Friction Reducing Structures of Synovial Joints

• 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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Stabilizing Features of Synovial Joints

• Stability is 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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Stabilizing Features of Synovial Joints

• 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

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Range of Motion of Synovial Joints

• 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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Range of Motion of Synovial Joints

• Gliding motion
• 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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Range of Motion of Synovial Joints

• Angular Motion
• 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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Range of Motion of Synovial Joints

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

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Range of Motion of Synovial Joints

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

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Range of Motion of Synovial Joints

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

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Types of Synovial Joints

• 1. Plane joints
• Articular surfaces are essentially flat
• Allow only slipping or gliding movements
• Only examples of nonaxial joints

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Types of Synovial Joints

• 2. Hinge joints
• Cylindrical projections of one bone fits into a
  trough-shaped surface on another
• Motion is along a single plane
• Uniaxial joints permit flexion and extension only
• Examples elbow and interphalangeal joints

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Types of Synovial Joints

• 2. Pivot joints
• Rounded end of one bone protrudes into a
  sleeve, or ring, composed of bone (and possibly
  ligaments) of another
• Only uniaxial movement allowed
• Examples joint between the axis and the dens,
  and the proximal radioulnar joint

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Types of Synovial Joints

• 2. Condyloid or Ellipsoidal joints
• Oval articular surface of one bone fits into a
  complementary depression in another
• Both articular surfaces are oval
• Biaxial joints permit all angular motions
• Examples radiocarpal (wrist) joints, and
  metacarpophalangeal (knuckle) joints

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Types of Synovial Joints

• 2. Saddle joints
• Similar to condyloid joints but allow greater
  movement
• Each articular surface has both a concave and a
  convex surface
• Example carpometacarpal joint of the thumb

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Types of Synovial Joints

• 2. Ball Socket joints
• A spherical or hemispherical head of one bone
  articulates with a cuplike socket of another
• Multiaxial joints permit the most freely moving
  synovial joints
• Examples shoulder and hip joints

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Functional Classification of Joints

• The three functional classes of joints are
• Synarthroses immovable
• Amphiarthroses slightly movable
• Diarthroses freely movable