Bone Cells

Bones are alive!

A bone is made of two things mixed together:

• Living bone cells that build and take care of the bone.
• Hard minerals, mostly calcium, that make bones strong like rock. A bendy stuff in there too keeps bones from snapping too easily.

Bones even have blood tubes to feed the cells, and nerves. That's why breaking a bone hurts!

The three bone cell jobs

Bone cells work as a team, like a building crew:

• Builders (osteoblasts), OSS-tee-oh-blasts, make new bone.
• Cleaners (osteoclasts), OSS-tee-oh-clasts, break down old or extra bone so it can be rebuilt.
• Keepers (osteocytes), OSS-tee-oh-sites, are builders that got trapped inside the hard bone they made! They live there and keep the bone healthy. They stay connected to each other through tiny tunnels.

Fixing a broken bone

When a bone breaks, the bone team gets to work:

• 1. Blood fills the break and makes a clot.
• 2. The body builds a soft bridge across the gap.
• 3. Builder cells turn the bridge into hard new bone.
• 4. Cleaner cells smooth it out until the bone is back in shape.

A cast holds the bone still so it heals straight. Kids' bones usually heal in a few weeks to a couple of months, faster than grown-ups' bones!

Keeping your bones strong

• Calcium makes bones hard. It's in milk, yogurt, cheese, and leafy greens.
• Vitamin D helps your body use calcium. Your skin makes it from sunshine, and it's in foods like fish and eggs.
• Jumping and running tell your builder cells to make bones thicker and stronger.

Bones also have a soft middle called bone marrow. That's where your red and white blood cells are made!

Bone cell quiz