Histology of Bone
Normal bone is lamellar - highly organised in mineralised plates, relatively hypocellular, and stress-
oriented. It can be cortical or cancellous.
Cortical bone makes up 80% of the skeleton, and is found in the outer shell of bone. It is composed of
tightly-packed osteons or Haversian systems, made up of small concentric lamellar cylinders surrounding a
central vascular channel, connected by Haversian (Volkmann’s) canals. These canals contain capillaries,
arterioles, venules, nerves and possibly lymphatics. Lying between these osteons are interstitial lamellae.
Fibrils often connect lamellae but do not cross cement lines, which form the outer border of osteons. The
intraosseous circulation provides nutrition. Cortical bone has a slow turnover rate, a relatively high Young’s
modulus, and a high resistance to bending and torsion.
Cancellous bone is less dense and more elastic than cortical bone, has a smaller Young’s modulus, and a
higher turnover rate. It is organised in trabecular struts, with lamellae running parallel to the trabeculae. It
is found in the epiphyseal and metaphyseal regions of long bones and throughout the interior of short
Immature or pathologic bone is woven and more random, with more osteocytes than lamellar bone. It is
the product of rapid bone formation, resulting in an irregular, disorganised pattern of collagen orientation
and osteocyte distribution. It is found in embryonic and foetal development, and in healthy adults at
ligament and tendon insertions. It also occurs in response to bony injury and dramatic changes in
mechanical stimulation. It provides a temporary mechanical adjunct to allow bone to maintain or return
quickly to its role as a structural support.
Osteoblasts form osteoid, the nonmineralised component of bone matrix. They differentiate from
mesenchymal progenitor cells, and contain extensive endoplasmic reticulum with multiple cisternae, well-
developed Golgi bodies, and numerous ribosomes and m