Human skeleton

Functions of the human skeleton

The human skeleton performs six major functions; support, movement, protection, production of blood cells, storage of minerals, and endocrine regulation.

1. Support

• The skeleton provides the framework which supports the body and maintains its shape.
• The pelvis, associated ligaments and muscles provide a floor for the pelvic structures.
• Without the rib cages, costal cartilages, and intercostal muscles, the lungs would collapse.

2. Movement

• The joints between bones allow movement, some allowing a wider range of movement than others, e.g. the ball and socket joint allows a greater range of movement than the pivot joint at the neck.
• Muscles, bones, and joints provide the principal mechanics for movement, all coordinated by the nervous system.

3. Protection

• The skeleton helps to protect our many vital internal organs from being damaged.
• The skull protects the brain
• The vertebrae protect the spinal cord.
• The rib cage, spine, and sternum protect the lungs, heart and major blood vessels.

4. Blood cell production

• The skeleton is the site of haematopoiesis, the development of blood cells that takes place in the bone marrow.
• In children, haematopoiesis occurs primarily in the marrow of the long bones such as the femur and tibia.
• In adults, it occurs mainly in the pelvis, cranium, vertebrae, and sternum.

5. Storage

• The bone matrix can store calcium for calcium metabolism, and bone marrow can store iron in ferritin for iron metabolism.
• However, bones are not entirely made of calcium, but a mixture of chondroitin sulfate and hydroxyapatite, the latter making up 70% of a bone.
• Hydroxyapatite is in turn composed of 39.8% of calcium, 41.4% of oxygen, 18.5% of phosphorus, and 0.2% of hydrogen by mass.
• Chondroitin sulfate is a sugar made up primarily of oxygen and carbon.

6. Endocrine regulation

• Bone cells release a hormone called osteocalcin, which contributes to the regulation of blood sugar (glucose) and fat deposition.
• Osteocalcin increases both the insulin secretion and sensitivity, in addition to boosting the number of insulin-producing cells and reducing stores of fat.