Final answer:
Compact bone is composed of osteons, which are the main structural unit. Osteons consist of a central Haversian canal surrounded by concentric lamellae. Spongy bone, which contains trabeculae, contrasts with the dense, outer layer structure of compact bone.
Step-by-step explanation:
Compact bone is composed of osteons, which are organized into rings. This dense matrix forms the outer surface of bone. Osteons are cylindrical structures that consist of a central Haversian canal surrounded by concentric rings known as lamellae. Within these rings are cavities called lacunae, which house osteocytes, and canaliculi, which are microchannels that facilitate communication between the cells.
Contrary to compact bone, spongy bone, also referred to as cancellous bone, is found on the interior of the bone and is made up of a web-like structure known as trabeculae. These trabeculae do not form the concentric patterns seen in compact bone but rather are arranged along lines of stress to provide strength to the bone. The spaces within some spongy bones are filled with red marrow, playing a crucial role in hematopoiesis, the production of blood cells.