Science of Bone building

About the "O" Bone Cells

It's fascinating and helpful to learn about bone cells and how they work together to repair broken bones. There are three special types of cells that are found only in the bone. Their names all start with "OSTEO"; the Greek word for bone.

Osteoclasts are the large cells that dissolve the bone. They come from the bone marrow and are related to white blood cells. They are formed from two or more cells that fuse together, so the osteoclasts usually have more than one nucleus. They are found on the surface of the bone mineral next to the dissolving bone.

Osteoblasts are the cells that form new bone. They also come from the bone marrow and are related to structural cells. They have only one nucleus. Osteoblasts work in teams to build bone. They produce new bone called "osteoid" which is made of bone collagen and other protein. Then they control calcium and mineral deposition. They are found on the surface of the new bone. When the team of osteoblasts has finished filing in a cavity, the cells become flat and look like pancakes. They line the surface of hte bone. These old osteoblasts are also called "Lining Cells". They regulate passage of calcium into and out of the bone, and they respond to hormones by making special proteins that activate the osteoclasts.

Osteocytes are cells inside the bone. They also come from osteoblasts. Some of the osteoblasts turn into osteocytes while the new bone is being formed, and the osteocytes then get surrounded by new bone. They are not isolated, however, because they send out long branches that connect to the other osteocytes. These cells can sense pressure or cracks in the bone and help to direct where osteoclasts will dissolve the bone.

How Bones Heal

We were made to heal. A cut on your arm is a good example of the healing process:

  • The cells die and then rebuild.  How fast the skin cells die and rebuild depends on how deep is the cut.
  • A surface cut on your arm will heal faster than a deep cut on your arm.
  • A deep cut requires  the skin to heal AND the muscle to heal and possibly tendons and/or ligaments to heal.

How fast cells heal is called “turnover” or for bones it is also referred as “remodeling of the bone”. The old or injured cells in your body die and slough off, and then new cells rebuild and heal.

Osteoclasts break down the bone getting rid of the old cells, and their cycle is 2 weeks. Osteoblasts make new cells and form  new bone, and their cycle is 3 months.

The exercises you do and the food you eat DO make a difference in how well you form new bone cells.