Bones are the primary components of the skeletal system that provide support, structure, and movement to the body.
While seemingly static, they are dynamic organs that also perform other physiological functions.
They are rich in minerals, particularly calcium and phosphate, and serve as storage reservoirs that help maintain mineral homeostasis in the body.
In addition to minerals, bones also store fat as an energy reserve. The yellow marrow found in the cavities of certain bones comprises adipocytes, or fat cells, that store lipids.
The yellow marrow also contains mesenchymal stem cells, which can differentiate into specialized cells of the bones and cartilage.
Another type, the red marrow, is present in the spongy bone cavities and in the center of flat bones, such as the pelvic girdle.
Red marrow contains hematopoietic stem cells, or HSCs, that can differentiate to produce different blood cells, including red blood cells, white blood cells, and platelets.
Towards the bone surface, cells called osteoblasts secrete the hormone osteocalcin, which regulates glucose homeostasis, cognitive functioning, and muscle exercise capacity.