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Bone 101


The bones that make up the skeleton are responsible for protection of our internal organs and maintaining mineral levels throughout the body in addition to providing a rigid structure required by the muscular system for movement.

Structurally, bone can be laid out in two different ways: cortical and cancellous bone.  Cortical bone is very dense and makes up the majority of our skeleton.  Cancellous bone, also referred to as trabecular bone, consists of narrow rods and plates that run between the cortical bone and help provide extra strength.  The amounts of cortical and cancellous bone vary depending on the amount of force that bone will be required to carry.  On a smaller scale, bone can be composed of both proteins and minerals.  The protein components allow bones to bend and return to their original shape, while the mineral component of bone provides the strength.  The balance between this strength and flexibility is important in avoiding fractures.  The ideal bone is strong enough to withstand heavy loads without breaking and flexible enough to return to its original shape after bending under a heavy load.

Bone is built and maintained by cells, the smallest living units within us.  The cells responsible for maintaining bone are osteoblasts, osteoclasts, and osteocytes.  The osteoblasts are responsible for building bone, while the osteoclasts destroy bone.  Osteocytes were originally osteoblasts that were “trapped” in the bone they formed. Osteocytes are thought to be involved in signaling.  Together these cells allow our skeleton to be broken down and rebuilt constantly to ensure our bones can carry out their intended uses.

Interesting Fact: Did you know you get essentially an entirely new skeleton every seven years?

written by Evan


Dempster, D.W., Anatomy and functions of the adult skeleton, in Primer on the metabolic bone diseases and disorders of mineral metabolism. 2006, The American Society for Bone and Mineral Research: Washington DC. p. 7-11.

The views expressed in this content represent the perspective and opinions of the author and may or may not represent the position of Indiana University School of Medicine.

Carl Pinkham