Knowledge of the composition, microscopic structure and function of bone.

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1. Composition of Bone: Bones are made up of several different substances. The outer layer of bone, known as the periosteum, contains blood vessels, nerves, and lymphatic vessels that nourish the bone. The hard outer layer of bones is composed of compact bone tissue, which is also called cortical bone. This part of the bone is about 80% of the skeletal mass and is responsible for the support and protection functions of the bones. Inside this layer is the trabecular bone, also known as cancellous or spongy bone, which is lighter and less dense than compact bone. It is found at the ends of long bones, in the pelvic bones, ribs, skull, and the vertebrae in the spinal column. The innermost part of the bone is the bone marrow, which produces blood cells.

2. Microscopic Structure of Bone: Under the microscope, bone tissue is an organic–inorganic composite material. The organic part is mainly composed of Type I collagen. The inorganic part is primarily made up of hydroxyapatite crystals, which give bone its hardness. Compact bone is organized into subunits called osteons, each consisting of concentric layers, or lamellae, of compact bone tissue that surround a central canal, the Haversian canal. The Haversian canal contains the bone's blood supplies. The space between osteons is occupied by interstitial lamellae, which are the remnants of osteons that were partially resorbed during the process of bone remodeling.

3. Function of Bone: Bones have many functions. They provide a framework for the body, protect organs, provide levers for movement, store and release minerals like calcium and phosphorus, and contain bone marrow, which produces blood cells.