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Skeletal System

SCIENCE MASTERPIECE

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Skeleton

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Joints

  • Joints are when 2 or more bones come together and help perform movement.
  • They can be classified by structure and by function.
    • There are joints that don’t move, slightly move, and freely move.

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Immovable

Slightly Moveable

Freely Moveable

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Immovable Joints

  • These joints are joined together by very strong connective tissue fibers.
  • Examples: Sutures and Pelvic Arch

Dense Fibrous

Connective Tissue

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Slightly Moveable Joints

  • These joints are connected by a ligament; a cord or band of fibrous tissue, or cartilage.
  • They lack a joint cavity.
  • The amount of movement depends on the length of the connecting fibers.
  • Example: Tibia and Fibula

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Freely Moveable Joints

  • These joints have articulating surfaces and joint cavities.
  • The bones have a special coating to help them move in the joint. The joint also has a special fluid to help the bones glide easily over each other.

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Ball and Socket Joint

  • The spherical of one bones sits in the cuplike socket of another bone.
  • These joints allow multiaxial movement.

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Hinge Joint

  • A cylindrical shaped bone fits in a trough shaped surface of the other bone.
  • Motion is in a single plane and looks like that of a door hinge.
  • Example: Knee and Elbow

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Pivot Joint

  • The rounded end of one bone fits into the sleeve or ring of the other bone.
  • The movement is uniaxial rotation of one bone around its own long axis.
  • Example: C1 and C2 of the spine

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Condyloid Joint

  • A knuckle-like or oval shaped surface of one bone fits into a concave surface of another bone.
  • Both surfaces are oval shaped.
  • These biaxial joints allow for angular motions: flexion and extension, abduction and adduction, and circumduction.
  • Example: Knuckles

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Saddle Joint

  • Similar to Condyloid but they allow for greater movement.
  • The joint surfaces have both concave and convex surfaces, making it shaped like a saddle.
  • Example: The thumb joint.

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Plane Joint

  • The joint surfaces are nearly flat.
  • This allows for only short gliding movements; gliding does not allow for rotation around any axis.
  • Example: Plane joint of the thumb.

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Common Joint Injuries

  • Sprains – Ligaments around a joint get stretched or torn. Common sites are ankle or knee.

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  • Dislocations – Occur when bones are forced out of alignment, they usually go along with a sprain. Common sites are shoulders, fingers, thumbs and jaw.

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  • Arthritis – There are over 100 different types. It can cause inflammation or degeneration. Ex: Osteoarthritis, Rheumatoid Arthritis, and Gouty Arthritis.

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Fun Bone Facts

  • Scientist can tell if a skeleton is male or female based on the pelvic bone.
  • Our red and white blood cells are made in our bones (bone marrow).
  • Ounce for ounce, bone is stronger than steel. One cubic inch of bone can withstand the weight of five standard pickup trucks, give or take a few pounds.
  • It takes about 4,000 newtons of force (900 lbs) to break the typical human femur.