ABSTRACT
Bone provides the strength and rigidity of the skeleton as well as acting as a reservoir of calcium and other mineral salts. It is a highly vascular, mineralized connective tissue of cells in a fibrous organic matrix permeated by inorganic bone salts. Cortical bone is always found on the outside of bones and surrounds the trabecular bone. Approximately 80% of the skeleton is cortical bone. Cortical bone is porous, but the ratio of solid tissue to space is considerably higher than for trabecular bone. Trabecular bone is found in the middle of bones such as the vertebrae, pelvis, and other flat bones, and at the ends of the long bones. There are three main types of bone cells: osteoblasts, osteoclasts, and osteocytes. Normal adult bone is termed lamellar bone. Each lamella is a thin plate 5–7 µm thick and made up of bone matrix consisting of protein fibers impregnated with bone salts.
