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Now, let us look into the subject of bone biology.
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Depicted here is a diagrammatic representation of a human long bone.
It has a periosteal surface and then endosteal surface.
Although a variety of bone tissue types may be formed,
shown here are the primary bone tissues circumferential
lamellae at the periosteal surface and trabeculae at the endosteal surface.
Subsequent to the laying down of primary bone tissues,
bone may be secondarily remodeled.
Shown here are the secondarily remodeled Haversian systems or osteons.
Osteons are formed for reasons of bone maintenance and repair.
Bone removing cells or osteoclasts,
remove a cylinder of bone typically about 50 to 200 microns in diameter.
A blood vessel invades this space together with
differentiating bone forming cells or osteoblasts and
new bone is laid down as osteonal
circumferential lamellae until they closely reach the diameter of the vessel.
Osteoblasts become incorporated into their own matrix as the tissue grows,
after which they are called osteocytes,
connected to one another in a network of cellular extensions.
A peculiarity of osteoblasts behavior,
is that when they lay down they're largely collagenous matrix.
They tend to preferentially orient the collagen they produce from
one lamellae to the other or else they alternate the orientation between lamellae.
Another thing to note is that because osteons may be produced in bone throughout life,
they will exhibit a mosaic of mineralization densities.
Older osteons being more dense than
younger osteons that have still to be fully mineralized.
Lastly, it should be noted that blood vessels also in anastomose
with the longitudinally oriented osteons to form Volkmann's canals.
Shown here is an image of osteonal bone from a human femur midshaft region,
