PATHOLOGY

Detailed explanation-1: -The hardness and rigidity of bone is due to the presence of mineral salt in the osteoid matrix, which is a crystalline complex of calcium and phosphate (hydroxyapatite). Calcified bone contains about 25% organic matrix (2-5% of which are cells), 5% water and 70% inorganic mineral (hydroxyapatite).

Detailed explanation-2: -A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility.

Detailed explanation-3: -Bone is a specialised connective tissue and together with cartilage forms the strong and rigid endoskeleton.

Detailed explanation-4: -Answer. Bones are hard and rigid because they are rich in calcium .