joints

• Immovable joints


  • As a person grows, some adjoining bones fuse
  • An infant's skull bones are joined by soft tissue that eventually hardens into bone, uniting the skull
  • These immovable joints are called sutures
• Pivot joints


  • The top two vertebrae fit together so that the lower one fits through the upper one to form a pivot for the skull
  • This arrangement allows the head to rotate and swivel
• Slightly movable joints


  • The vertebrae have pads of cartilage between them that allow only limited movement
• Ball-and-socket joints


  • A ball-shaped head moves within a hollow socket
  • This design creates rotating movement and allows free movement in all directions
  • The hip and shoulder joints are ball-and-socket joints
• Hinge joints


  • The bones at these joints fit together so that they bend in only one direction
  • The knee and elbow are hinge joints
• Gliding joints


  • The wrist and ankle bones have slightly convex and concave surfaces that fit together to allow limited lateral and vertical movement
• Axial skeleton


  Comprised of 80 bones, including the skull, ribs, sternum, and vertebral column
• Appendicular skeleton


  126 bones found in the arms, legs, and pectoral and pelvic girdles
• Irregular bones


  • Jaw bone
  • Vertebrae
  • Other bones that have a variety of shapes and do not fit into any of the other categories
• Joints


  • Relate to the ends of bones
  • Covered by a joint capsule
  • Lined by synovial membrane that produces synovial fluid
  • Sac-like structures called bursas located between moving parts to reduce friction
• While most of the cartilage in a child's bones ossifies, some cartilage remains at the very ends of the bones to cushion them where they meet at a joint
• Strong bands of connective tissue called ligaments attach to the periosteum, the bone's outer covering, to hold the bones together
• The ribs are some of the flat bones
• The long bones make up the arms and legs
• The carpals and tarsals, located in the hands and feet respectively, are good examples of short bones