Biomedical Engineering Reference
In-Depth Information
Figure 1.16
Compact bone - ground cross
section. System of osteons that is visible in
transverse histological section of the cortical
bone. Haversian canals (large dark circular
holes) are surrounded by the rings of lamel-
lae. The Haversian canal in the center of the
osteon has a diameter ranging between 50
and 90
µ
m. The smaller dark circles or el-
lipses (one is indicated by white arrow) are
lacunar spaces within the osteon. In lacunae,
the bone cells - osteocytes - are sheltered.
Volkmann's canals, linking Haversian ones,
arealsoseeninthelowerpartofthefigure.
Courtesy of Litwin and Gajda.
Impressive microphotographs, being the images of osteon in large magnification,
obtained by means of scanning electron microscopy (SEM), were provided by
Frasca
et al
. [114]. The arrangements of collagen fibers in lamellae are shown
here, for example, decalcified osteon sample with exposed lamellar interfaces
(
1000), and
complex fiber arrangement in one lamella, with partial stripping of two sequential
lamellae.
The manner in which the crystals and the collagen fibrils are organized in the
osteon has still not been resolved, even though it is known that they are intimately
related.
Weiner, Arad, and Traub observed in 1991 that the plate-shaped crystals of
rat bone are arranged in parallel layers that form coherent structures up to the
level of individual lamellae. The crystal layers of the thin lamellae are parallel to
the lamellar boundary, whereas those of the thicker lamellae are oblique to the
boundary. The basic structure of rat bone can be described as
rotated plywood
[115].
Enlow in his microscopic study of the bone at the tissue level considered that
a bone section is always a slice at the time of ontogeny. The actual tissue types
express the succession of events that took place at that very level during bone
development [116].
×
200), coexisting longitudinal and transverse fibers in one lamella (
×
