Cortical bone: also known as compact bone, is one of two main types of osseous tissue. Cortical bone is dense and forms the surface of bones. It is solid in appearance, and constitutes 80% of total bone mass. Compact bone is composed of many cylinder shaped units called osteons, or Haversian Systems (after the anatomist who discovered them.) and transverse channels between them called Volkmann's Canal
Cancellous bone, synonymous with trabecular bone or spongy bone, is one of two types of osseous tissue that form bones. Compared to compact bone, which is the other type of osseous tissue, it has a higher surface area but is less dense, softer, weaker, and less stiff. It typically occurs at the ends of long bones, proximal to joints and within the interior of vertebrae. Cancellous bone is highly vascular and frequently contains red bone marrow where hematopoiesis, the production of blood cells, occurs. The primary anatomical and functional unit of cancellous bone is the trabecula.
The bone usually forms initially as cancellous bone and then forms the compact bone.