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�����General Anatomy� ��The Skeletal System 4���

Joints of the Skeletal System

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Joints of the Skeletal System

  • Also called articulations.
  • Functional junctions between bones.
  • Bind parts of skeletal system together.
  • Make bone growth possible.
  • Permit parts of the skeleton to change shape during childbirth.
  • Enable body to move in response to skeletal muscle contraction.

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Naming of Joints

  • Usually derived from the names of the articulating bones.

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Classification of Joints

According to structure:

  • Fibrous Joints
    • Dense connective tissues connect bones
    • Between bones in close contact
  • Cartilaginous Joints
    • Hyaline cartilage or fibrocartilage connect bones
  • Synovial Joints
    • Most complex
    • Allow free movement

According to mobility:

  • Synarthrotic
    • Immovable
  • Amphiarthrotic
    • Slightly movable
  • Diarthrotic
    • Freely movable

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Fibrous Joints

3 Types

    • Syndesmosis
    • Suture
    • Gomphosis

1. Syndesmosis:

    • A sheet or bundle of fibrous tissue connects bones.
    • Amphiarthrotic.
    • Lies between tibia and fibula.

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Fibrous Joints

2. Suture:

    • Between flat bones.
    • Synarthrotic.
    • Thin layer of connective tissue connects bones.

3. Gomphosis:

    • Cone-shaped bony process in a socket.
    • Tooth in jawbone.
    • Synarthrotic.

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Cartilaginous Joints

2 Types

    • Synchondrosis (hyaline)
    • Symphysis (fibrocartilage)

1. Synchondrosis:

    • Bands of hyaline cartilage unite bones.
    • Could be temporary (e.g., Epiphyseal plate).
    • Or permanent (e.g., the sternocostal joint between manubrium and first rib).
    • Synarthrotic (immovable).

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Cartilaginous Joints

2. Symphysis:

    • Pad of fibrocartilage between bones.
    • Examples:
      • Pubis symphysis.
      • The intervertebral disc between two vertebrae
    • Amphiarthrotic (slightly movable) and permanent.

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General Anatomy of Synovial Joints

  • Basic features:
    • Articular capsule.
    • Joint cavity.
    • Synovial fluid.
    • Articular cartilage.
    • Ligaments.
    • Nerves.
    • Blood vessels.

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General Anatomy of Synovial Joints – Accessory Structures

  • Bursae
    • fibrous, saclike structure that contains synovial fluid and is lined by a synovial membrane.
    • Usually located next to the tendons near the large joints
    • reduce friction between tissues of the body.
  • Fatpads
    • often distributed along the periphery of a synovial joint
    • act as packing material and provide some protection for the joint
    • fill the spaces that form when bones move and the joint cavity changes shape
  • Tendons
    • attaches a muscle to a bone
    • help stabilize joints

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A tendon sheath can be understood as a lengthened bursae wrapping totally around a tendon that is subjected to friction.

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Types of Synovial Joints

  • Classified by the shapes of their articulating surfaces.
  • Types of movement they allow:
    • Uniaxial if the bone moves in just one plane
    • Biaxial if the bone moves in two planes
    • Multiaxial (or triaxial) if the bone moves in multiple planes

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Types of Synovial Joints

  • From least movable to most freely movable, the six specific types of synovial joints are➘:
  • Planar (gliding) joints
  • Hinge joints
  • Pivot joints
  • Condyloid (ellipsoid) joints
  • Saddle joints
  • Ball-and-socket joints

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Types of Synovial Joints

1. Gliding Joint

    • Between carpals
    • Between tarsals

2. Hinge Joint

    • Elbow
    • Between phalanges

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Types of Synovial Joints

3. Pivot joint

    • Between proximal ends of radius and ulna
    • Between the atlas and axis

4. Saddle joint

    • Between carpal and metacarpal bones of the thumb

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Types of Synovial Joints

5. Ball-and-Socket Joint

    • Hip
    • Shoulder

6. Condyloid Joint

    • Between metacarpals and phalanges

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Types of Synovial Joints

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Mobility and Stability in Joints

  • Motion permitted ranges from none to various extensive motions.
  • Structure determines both its mobility and its stability.
    • more mobile = less stable

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Types of Joint Movements

  • Abduction/adduction
  • Dorsiflexion/plantar flexion
  • Flexion/extension/hyperextension

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Types of Joint Movements

  • Rotation/circumduction
  • Supination/pronation

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Types of Joint Movements

  • Eversion/inversion
  • Protraction/retraction
  • Elevation/depression

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Life-Span Changes

  • Joint stiffness is an early sign of aging.
  • Fibrous joints first to change; can strengthen over a lifetime.
  • Changes in symphysis joints of vertebral column diminish flexibility and decrease height.
  • Synovial joints lose elasticity.
  • Disuse hampers the blood supply.
  • Activity and exercise can keep joints functional longer.

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