Bone classes

• There are 4 bone classes:

  • Long bones
  • Short bones
  • Flat bones
  • Irregular bones
• Long bones

  • They are longer than they are wide, so they contain a narow shaft.
  • Composed of a wider epiphyses (end part of bone growing seprately from the shaft) and a narrower diaphysis.
• The narrow diaphysis of a long bone is made up of compact bone and the shaft is made up of cancellous bones.
• Long bones act as levers for movement, allowing long limbs to move.
• The proximal epiphysis contains the most cancellous bone, however contains a lot of compact bone to take the weight in.
• The medullary cavity is filled with red/yellow marrow.
• Short bones

  • They are equal in length and width
  • Mostly made up of cancellous bone (weaker).
  • No compact bones, only on the outer parts (thin layer) because of shock absorbing.
  • Weight bearing from multiple directions and can resist a lot of force.
• Flat bones

  • They are usually everyone because they provide a large surface area for muscles to attach on.
  • they are able to protect and are thin plates of compact bones.
• Irregular bones

  • They come in various shapes and sizes
  • not long
  • Not square
  • Not just cancellous bones
  • Often have foramina (lots of holes), so other bones can fit through.