BONES
Skeleton includes bones and cartilages. Definition of Bone Bone is a living tissue that makes up the skeleton of the body. Composition of Bone: Bone is composed of inorganic calcium salts. It consist mainly of calcium phosphate and partly of calcium carbonate. The inorganic calcium salt is calcium hydroxy-apatite [Ca 10 (PO 4 ) 6 (OH) 2 ] It also consist of the organic connective tissue made up of collagen fibres. Functions of Bones: It gives shape and support to the body. Bones contain bone marrow. Bone marrow contains the reticuloendothelial cells, these cells are phagocytic in nature and take part in immune responses of the body. Bone marrow also helps to manufacture the blood cells. Bones provides the surface for the attachment of muscles, tendons and ligaments. They store about 97% of the body's calcium and phosphorous. They protect the vital organs of body e.g. Skull protects the brain, vertebral column protects the spinal cord.