There are two types of bone; cortical (or compact), and trabecular (or cancellous). Cortical bone is present in long bone shafts of the appendicular skeleton, while trabecular or cancellous bone is the flat plates of bone which criss-cross the marrow cavity. The latter type of bone is in intimate contact with the cells of the marrow cavity and is probably metabolically regulated by these cells and their products. The axial skeleton, the vertebrae, and the proximal ends of long bones are rich in trabecular bone. The skeleton is comprised of eighty per cent cortical bone and twenty per cent trabecular bone.
