Bones have to withstand a great deal of pressure in everyday life. They carry our body weight and take on various strains whenever we stand and move around. Their structure and ability to adjust to physical strain make it possible to withstand this stress. Bones are not a rigid frame, but living tissue. Like all other tissues and organs of the body, bones are constantly renewed.
The outer layer of a bone is called compact or cortical bone. This layer is hard and particularly solid, and it makes sure that our bones can withstand daily physical strains. The outer layer has a thin coating called the periosteum.
Inside bones there is a supporting structure with interconnecting bony plates and rods called trabeculae. This structure is called trabecular or spongy bone because it looks a bit like sponge. Bone marrow is found in the “holes” of the spongy bone. Many of the bones contain red bone marrow at birth. Red bone marrow produces the blood cells. The longer we live, the more red bone marrow turns into fatty tissue. In adults, red bone marrow is only found in a few bones, for example in the ribs, the sternum (breastbone), and the pelvic bones.