Bone and Cartilage – its Structure and Physical Properties - Biomechanics of Hard Tissues - page 24

functions. The macropores give space to permit bone cells to grow and allow blood
to circulate, and the micropores facilitate the cell adhesion and crystallization of
bone structure.

1.3.2
Osteon

The principal organizing unit of the compact bone is the osteon. A synonym for
osteon is Haversian system. The osteon can be approximated as a long narrow
cylinder that is 0 . 2 mm (200 µm) wide and 10 mm long. Osteons are found in the
bones of mammals, birds, reptiles, and amphibians, running in a meandering way
but generally parallel to the long axis of bones. Morphology of the osteon, obtained
by electron microscopic techniques, for the study of compact bone is given in [89].
When the compact bone osteons are being formed, collagen fibers are laid
down first. The collagen patterns are reflected in the structure known as a lamella .
Osteons have between 4 and 20 lamellae with each measuring between 3 and 7 µm
in width.
Leeuwenhoek, the father of microbiology, had reported his observations of the
canal system in bones to the Royal Society of London in 1678. He called the canals
pipes , and pointed out that they run both longitudinally and transversely in bones
[90-92]. Thirteen years later, Havers did provide a more extensive description of
the canal system in bones, linking it with his ideas of the lamellar nature of the
bone tissue [93]; see also [94-96].
The group of cells functioning as an organized unit was called basic multicellular
unit or bone multicellular unit (BMU) by Frost [97-100]. Remodeling process
occurs with a specific sequence of events in the BMU.
The microscopic structure of a mammalian compact bone consists of repeating
units called osteons or Haversian systems . Each system has concentric layers of
mineralized matrix, called concentric lamellae , which are deposited around a central
canal, also known as the Haversian canal , containing blood vessels and nerves
that service the bone. By the longitudinal axis of the osteon runs a central canal,
called the Haversian canal (synonyms: Canalis nutricius , Canalis nutriens , Haversian
space, nutrient canal of bone) [101-103]. The elements of the osteon are shown in
Figure 1.13.
The central canal is surrounded by concentric layers of matrix called lamellae .
Thelamellaearelaiddownoneaftertheotherovertime,eachsuccessiveoneinside

Cement

Lacuna

Canal

Lamella

Canaliculi

Figure 1.13 Elements of an osteon. After [87]. With
permission of the author Blystone.