Question

What are bones made of? Are the bones living or non living? Give reasons.

Answer 1

(i) Bone is a strong, hollow and non-flexible connective tissue.

(ii) It is hard, greyish-white tissue, composed of 2/3^rd of inorganic substances or minerals like calcium, phosphorus, carbonates, etc. and 1/3^rd of organic substances.

(iii) The outer surface of the bone is called periosteum. Periosteum is a thin, dense membrane that consists of outer fibrous and inner cellular layer, nerves and blood vessels that nourish the bone.

(iv) The next layer is made up of compact bone. This part is highly calcified, very hard and rigid connective tissue. This tissue gives bones a smooth, white and solid appearance.

(v) The middle layer of bone consists of bone cells called osteocytes, which are arranged in the form of concentric rings. They are embedded in a hard matrix made up of collagen fibre and mineral deposits.

(vi) The innermost hollow cavity of long bones contains bone marrow, which produces blood cells. Red bone marrow is present at the ends of the bone and produces majority of red blood cells, platelets and most of the white blood cells. Yellow bone marrow contains higher amount of fat cells than red marrow and helps in the production some white blood cells.

(vii) Bones are living tissue as long as they are present in the living body. However, when they are taken out of the body, their cells die and the bones are then said to be dead.