Periosteum

Bones are made up nerve cells, blood vessels and living bone cells (osteocycles) which are held together by a hard non-living material containing calcium and phosphorus. Periosteum is a thin membrane which covers the bones surface. Long bones are made up of various sections which are; the diaphysis which is the long central shaft, metaphysis which is the area between the diaphysis and epiphysis placed at the end of the bone, the distal and proximal epiphysis which forms the large rounded ends of bones. Epiphyseal plates are made of cartilage and allow bones to grow in length, the articular cartilage covers the ends of bones allowing joints to be formed, and it is a smooth white tissue and is a firm elasticated type of cartilage which has shock
absorption. The marrow cavity is in the centre of the bone, it contains red bone marrow which is where most red blood cells are produced and yellow bone marrow which is mainly fatty tissue.
Bones which are compacted are dense and form the outer layer of bones. Spongy bones are light weight and made up of tiny pieces of bone with larger spaces between them. Muscles and tissue are attached to bones which act as a framework to support the body. The skeleton also acts a protection for internal organs, give muscles area to attach and acts as a reservoir for calcium and phosphorus. Within the marrow of the bone blood cells are produced and lipids act as an energy reservoir.