L4.4.1: Bone Cells

• Bone Cells

  • osteogenic (osteoprogenitor) cell
  • osteoblast
  • osteocyte
  • osteoclast
• OSTEOGENIC (OSTEOPROGENITOR) CELL

  ● Are undifferentiated with high mitotic activity and they are the only bone cells that divide

  ● Do not have mature structure or function

  ● Not developed into specialized cell
• OSTEOBLAST

  ● Is the bone cell responsible for forming new bone and is found in the growing portions of bone, including the endosteum and the cellular layer of the periosteum

  ● Endosteum - covering of the bone found in the inner lining of the medullary cavity

  ● Periosteum - covering of the bone found in the outer lining along the diaphysis. Has 2 layers:

  ○ Fibrous layer

  ○ Cellular layer - where osteoblast is found
• OSTEOCYTE

  ● Is the primary cell of mature bone and most common type of bone cell
• OSTEOCLAST

  ● Are cells responsible for bone resorption, or breakdown
• ● The bone is relatively lightweight and resists tension and other forces.

  ● Organic parts (collagen fibers) of the bone contribute to its flexibility and great tensile strength.

  ● Calcium salts deposited make bones hard in order to resist compression – Hydroxyapatite Crystals
• Osteogenic Cell – Osteoprogenitor

  ○ Undifferentiated cells with high mitotic activity.

  ■ No specialized functions or mature structure. Not yet developed.

  ○ The only bone cells that divide.
• Osteoblast

  ○ Responsible for forming new bones by secreting

  bone matrix and turning proteins into new tissue.

  ○ Location: Growing portions of the bone, endosteum

  and the cellular layer of the periosteum.
• Osteocyte

  ○ Primary cell of mature bone

  ○ Most common type of bone cell.
• Osteoclast

  ○ Responsible for breaking down damaged and dead bone tissues and bone resorption.

  ○ Results in a transfer of calcium from bone tissue to the blood.