A description of the various histological types of mineralized tissues that form bones, their biomechanics, and the approaches that are used to model such biomechanical behavior at the tissue scale.

Overview

In our journey from the organism to the molecules, we have now reached the tissue scale. Here the bone cannot be assumed as a continuum, as in Chapter 4, but we need to consider the histology, i.e. the microscopic anatomy of the tissue. Whereas gross anatomy describes organs as visible to the naked eye, so histological anatomy describes the structure and organization of the tissues that form such organs as observable with microscopes. Traditionally, histology involves: the fixation of a portion of tissue, so as to preserve it indefinitely; dehydration and infiltration with an embedding material, where dehydration is necessary because the water always present in the living tissues prevents the tissue from being infiltrated by the embedding material; sectioning, where the embedded tissue is sliced thinly, so that the slices become transparent to light; staining, which uses chemical reactions to color specific compounds and structures inside the tissue, and render them visible; and the microscope observation, which today can be done with a vast number of devices including scanning electron microscopy, laser confocal microscopy, etc.

Bone tissue is a composite material, made of a complex texture of collagen fibers that is mineralized by crystals of hydroxylapatite, also called hydroxyapatite, a naturally occurring mineral form of calcium apatite with the formula Ca10(PO4)6(OH)2 (Weiner and Traub, 1992).