|The bones in the skeleton are not all solid. The outside cortical bone is solid bone with only a few small canals. The insides of the bone contain trabecular bone which is like scaffolding or a honey-comb. The spaces between the bone are filled with fluid bone marrow cells, which make the blood, and some fat cells.
You can see the difference youself at the grocery store meat department. Here is a photograph of a T-bone steak.
|Here is a close-up picture of a piece of the pelvic bone. It was put into a special kind of xray machine which gives lots of details. The photograph is used with permission from Dr. Yebin Jiang from University of California, San Francisco.
If all the bones were solid, think how heavy they would be.
It would be hard to run!
The next page is about the cells inside the bones.