Bones are hard, rigid structures that form the human skeletal system. They are dynamic organs that undergo constant changes in response to environmental stimuli. They can fuse together (human babies are born with around 300 bones while there are only about 206 bones in an adult human), increase or decrease in size, thin down or thicken, or strengthen further as needed. When broken, such as in the case of injury, the bones can regenerate without leaving scar tissue.
The bones important functions including the following:
- Provide support, structure, and shape to the human body
- Protect vital, delicate organs
- Produce white and red blood cells as well as other marrow-derived cells produced by stem cells, which lie in the innermost layer of the bone (marrow)
- Facilitate respiration
- Store fat and minerals that are made available as the body needs them, thereby playing an important role in homeostasis
Allows motor and locomotive function, in coordination with muscles and joints that connect bones together
Bones are made of four types of cells: osteocytes, osteoclasts, osteoblasts, and lining cells.
Osteoblasts are the ones that make new bones as the body grows. Osteoblasts, when come together, create a flexible material called osteoid, which when fused with minerals, become hard and strong. Osteoblasts are also the ones responsible for rebuilding existing bones in case of fracture or injury.
Osteocytes, which are commonly found on compact bones that support the body and muscles, are star-shaped cells that exchange minerals with other cells in the area.
Lining cells – These cover the outside surface of the bones which main function is to control the movements of molecules found inside and outside of the bone.
Osteoclasts – These are cells that break down to reabsorb existing bone. They also work together with osteoblasts to reshape bones in cases of bone problems such as fracture.
Common Bone Problems/Conditions
Osteoporosis – A condition common in older adults characterized by loss of bone mass and weakening of the bone structure. This leads to the loss of bone density making bones more susceptible to breakage and fractures.
Paget’s disease – A condition wherein bones become abnormally enlarged and thickened yet brittle and fragile. This is caused by a disorder that prevents bone cells from rebuilding and re-molding bone tissue.
Rickets/Osteomalacia – A bone disease also characterized by brittle and weak bones and is linked to vitamin D deficiency
Acromegaly – A bone disease caused by the overproduction of growth hormone in the body, leading to overgrown bone structures in the face and extremities
Bone cancer – A cancer that affects the bones either directly or through metastasis from cancer in another part of the body
Osteomyelitis – A bacterial infection leading to the inflammation of the bone or bone marrow
Common Bone Procedures and Surgeries
Bone fracture repair – Minor bone fractures are usually treated with splinting or casting. However, major bone fractures may require a surgical procedure called open reduction and internal fixation (ORIF) surgery that involves the use of metal screws, rods, pins or plates to hold the affected bone in place.
Bone grafting - This refers to a range of surgical methods performed to stimulate the formation of new bones. This minimally invasive procedure involves adding tissues to specific areas to induce bone-forming cells.
Surgical cleansing – Bone infections and osteomyelitis are often treated surgically wherein bones are accessed through the skin and cleansed with antibiotics.
Bone rebuilding – Bones that are severely damaged or infected are rebuilt through a variety of ways, including bone grafting, bone transport or the use of an external fixator.
Bone biopsy – Usually done to confirm bone cancer diagnosis or to investigate abnormal growths, a bone biopsy is a procedure where a small sample of a bone is removed and examined.