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Introduction to Bone Remodeling

Introduction to Bone Remodeling

Author: Aaron Mullally

- Describe the importance of bone remodeling in regard to bone density

- Identify that mechanical stress has the greatest influence over bone remodeling

- Describe the role that osteoclasts and osteoblasts play in the remodeling process

- Define the term deposition; also identify the cells are involved with this process

- Define the term resorption; also identify cells are involved with this process

This packet will introduce you to the process of bone remodeling. This is a term used to describe how bones increase and decrease their density.

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Overview of Remodeling

This packet will introduce you to the concept of bone remodeling and how it influences bone density. As mentioned in previous packets bone is a very dynamic tissue. Bone is constantly adding layers and stripping layers of tissue off of itself. Remember that 1/3 of bone is organic i.e. cells and fibers. This organic material needs to be replaced as it dies. So as the organic material deteriorates bone density does as well. As we replace the old organic material with the new, bone density increases.

Bones also remodel based on how much mechanical stress is applied to them, known as Wolfe's Law. This is a relatively simple concept to understand. The more stress (mechanical force) that is applied to the bone the thicker it will become. Conversely, the less stress that is applied to bones the thinner it will become. The main source of the mechanical stress are skeletal muscles. Remember that when a skeletal muscle contracts it shortens. When the muscle shortens it pulls on its tendonous attachments to the bones, forcing them to thicken. If the bones didn't thicken the muscles could do some serious damage to the bones. Athletic, physically active people tend to have bones that are thicker due to the constant force applied to them because of the repetitive, forceful muscle contractions.

On the flip side if a person is inactive they will have a smaller bone density. If a person was athletic all through high school and then became sedentary afterwards, for whatever reasons, their bone density will thin. Do you know anyone that has ever become a paraplegic later in life? Take notice of their legs and how thin they become. As the muscles in the legs deteriorate the bones become thin as well. (sorry for the depressing example).

The process of adding more tissue to bone is called deposition and this is conducted by osteoblasts. The process of stripping tissue from bone is called resorption, and this is conducted by osteoclasts. If deposition occurs more frequently than resorption then bone density will increase. If resorption occurs more frequently then bone density will decrease.

Source: The mind of Aaron

Introduction to Remodeling

This video will introduce you to bone remodeling and some new terms that go with the process

Source: Self made

Remodeling High Points

Source: Self made

Peer Reviewd Example of Remodeling

Here is a peer reviewed journal article about this very concept