Structural classification of bone

Macroscopically, bone tissue can be classified into two types, compact and trabecular bone. Compact bone is dense, corticated and makes up the outer surfaces of most of the bones of the skeleton. Trabecular bone is spongy, cancellous and constitutes the inner surfaces of bones, also containing the medullary cavity or marrow.

Microscopically they are identified as two types, the  immature (woven) and mature (lamellar) bone. Immature bone is formed earlier and more rapidly than mature bone, and is the first type to form in a repair situation or around an implant. In mostcases mature bone will then replace the immature bone.