Biomedical Engineering Reference
In-Depth Information
Figure 1.2:
Proteoglycans and collagen contents vary throughout the zones of cartilage.
causes rapid pressurization of the fluid in the tissue, which in turn supports the load (Figure 1.3).
This mechanism allows for the longevity of cartilage under repeated compression since loading is
borne by fluid instead of a solid-solid interaction [
7
,
8
].
1.1.1.2 Collagens
Collagens serve a primary role in the structure of connective tissues throughout the body. They are
comprised of repeating amino acid sequences (glycine, proline, hydroxyproline, etc.) and exhibit a
characteristic triple helix structure. Collagen type II is the predominant collagen type in articular
cartilage, comprising over half the dry weight of the tissue [
9
]. Collagen fiber orientation varies
through the depth of articular cartilage with the superficial zone containing tangentially arranged
fibers, the deep zone containing radially oriented fibers, and the middle zone having both an arcade-
like structure and randomly oriented fibers that forms the transition between the other zones [
10
]
(Figure 1.4).
Hyaline cartilage also contains other fibrillar and globular collagen types, such as types V, VI,
IX, and XI [
11
]. While the definitive roles of these other collagen types are not fully known, they are
believed to play a role in intermolecular interactions as well as modulating the structure of collagen
