Final answer:
Bone tissue comprises of both compact bone, the dense outer layer, and spongy bone, the porous inner part.
Step-by-step explanation:
The two main things that comprise bone tissue are compact bone and spongy bone. Compact bone, or cortical bone tissue, is the denser, harder outer layer of the bone that provides most of the bone's structural strength. On the other hand, spongy bone, also known as cancellous or trabecular bone tissue, contains trabeculae and is found in the interior parts of the bone, such as the ends of long bones, and is lighter and more porous than compact bone.
Bone, or osseous tissue, includes specialized cells and a matrix that consists of collagen fibers and mineral salts, primarily calcium and phosphorus, in the form of hydroxyapatite, which are responsible for bone's strength and flexibility. Osteocytes are the bone cells that maintain the bone matrix, and the ongoing remodeling of bone tissue is facilitated by the activity of osteoblasts, which build up the bone, and osteoclasts, which break down bone tissue.