Our bones are usually considered little more than lifeless pillars on which to base our more important systems. However, contrary to popular misconception, bones are as alive as the muscles and organs that cling on to them for support, and are buzzing hives of living cells.
Did You Know?The prefix 'osteo' comes from the Greek word for bone. It is used in many bone-related words apart from the subjects of this write-up; for instance, osteoporosis and osteosarcoma are both conditions related to the bone.
Osteoblasts, osteocytes, and osteoclasts are interrelated types of cells found in the bone. Named after the Greek word for 'bone', these cells perform specific functions within the bone. Here's a summary of the roles the three perform.
Osteocytes are cells that form the bones themselves, osteoblasts are responsible for the formation of new osteocytes, whereas osteoclasts are responsible for the resorption of old bone matter. Thus, between them, the three types of bone cells regulate the formation, sustenance, and decay of bones. It is a constant process and is carried out for an individual's entire lifetime. A disorder related to either one of the three is disastrous for bone health, since all three, even the osteoclasts, are vital.
These three are part of an osteon, which is a functional unit of compact bone matter. Bones have two types of tissues: the hard, strong exterior and the spongy interior marrow. Osteocytes, osteoblasts, and osteoclasts are found on the outer side of bones.
Internal structure of a bone and an osteon
These cells form the cycle of bone remodeling, as illustrated in the diagram below:
The function of all three of these cells is crucial to healthy bones. One may think osteoclasts are actually harmful for the body, but bones aren't the only sites in the body where calcium is needed, and osteoclasts do the sometimes-vital task of making calcium available. If sufficient calcium intake is maintained and weight-bearing activities are performed regularly, osteoclasts are suppressed and the number of osteoblasts increases, resulting in a greater bone density.