Calcium and other salts make the bone strong but slightly flexible. Bone is a living tissue with a blood supply. It is a mixture of soft living material and hard salts. Look at the microscopic view shown to see how bone is deposited in rings around blood vessels. Bone is constantly being dissolved and laid down.
Bone is a dynamic tissue in constant change.
It has very few nerve connections. The cells in the marrow of long bones in the body are responsible for producing blood cells. The skeleton contains more than 200 bones which support and protect the body.