Biomedical Engineering Reference
In-Depth Information
Fig. 2.2 a
A 5-mm-thick histological sections of fresh healthy human articular cartilage after
staining with haematoxylin-eosin showing the chondrocytes in the ECM.
b
A 5-mm-thick histolog-
ical sections of newly formed bone within a HAp scaffold after staining with haematoxylin-eosin
showing the ECM, osteocytes, osteoblasts and bone lining cells
Histological properties and health of cartilage and its mechanical properties are
interrelated. For example, the Young's modulus of human cartilage decreases with
increasing degrees of degeneration [
21
]. The ECM provides the tissue's mechanical
and biochemical properties and affects cellular function by cell-matrix interactions
[
22
]. The ECM has two phases: a fluid phase and a solid organic matrix that is mainly
composed of collagens, non-collagenous proteins, and proteoglycans (PGs). The fluid
phase is mainly composed of water, and some of the water is free and can move in and
out of the tissue [
19
]. Water constitutes 65-85% of the weight of the cartilage. Water
is important for processes such as the transport of nutrients and wastes into/from the
tissue, and the lubrication of the gap between articulating surfaces. Water content of
the cartilage can be affected by pathological conditions, for instance in osteoarthritic
