Biomedical Engineering Reference
In-Depth Information
Fig. 2.13
Arrangement of dense but irregularly packed collagen fibers in joint cartilage, sparsely
seeded with fibroblasts (
encircled
) responsible for auto-repair. On the contrary, in ligaments or ten-
dons the fibers are highly organized. Reproduced from Gray's Anatomy [52], Fig. 1.77. Copyright
Elsevier, 2010
Viscoelastic Fluids
The fourth class are the
viscoelastic
fluids which exhibit partly Newtonian behavior
for the viscous component and partly elastic (Hookean) behavior.
In Chap. 11, we will have to come back on this issue when discussing polymers.
The purpose of this parenthesis was to make a link between what was said about
synovial fluids to the physics and flowing fluid
rheology
. In the human body, almost
nothing flows in a Newtonian way: complex viscosity is of basic biological interest.
According to the definition in anatomy, the matrix consists of cells, chondrocytes
and chondroblasts, and a complex watery gel with high content of carbohydrates.
Collagen fibers mainly of type II are imbedded in the matrix. Figure
2.13
is an
example of irregularly stapled collagen as present in joint cartilage. They represent
about 50% of its dry weight. The fibers form a 3D network which is interlinked
with proteoglycans, long chain carbohydrates bearing sulfate and carboxyl groups
and covalently linked to a core protein and, subsequently assembled into filamentous
aggregates. For obvious reasons, glucosamine sulfates are popular pharmaceutical
products, promising to reduce cartilage wear and regeneration. Is it hype or a miracle
drug?
