Bone is often stereotyped as simply a protective and supportive framework for the body. Though it does perform these functions, bone is actually a very dynamic organ that is constantly remodeling and changing shape to adapt to the daily forces placed upon it. Moreover, bone stores crucial nutrients, minerals, and lipids and produces blood cells that nourish the body and play a vital role in protecting the body against infection. All these functions make the approximately 206 bones of the human body an organ that is essential to our daily existence.
The skeletal system consists of bones, cartilage, and the membranes that line the bones. Each bone is an organ that includes nervous tissue, epithelial tissue (within the blood vessels), and connective tissue (blood, bone, cartilage, adipose, and fibrous connective tissue).
Bones have many functions, including the following:
- Support: Bones provide a framework for the attachment of muscles and other tissues.
- Protection: Bones such as the skull and rib cage protect internal organs from injury.
- Movement: Bones enable body movements by acting as levers and points of attachment for muscles.
- Mineral storage: Bones serve as a reservoir for calcium and phosphorus, essential minerals for various cellular activities throughout the body.
- Blood cell production: The production of blood cells, or hematopoiesis, occurs in the red marrow found within the cavities of certain bones.
- Energy storage: Lipids, such as fats, stored in adipose cells of the yellow marrow serve as an energy reservoir.