Biomedical Engineering Reference
In-Depth Information
11.4
The spongy bone can withstand stresses that arrive from multiple directions, whereas
compact bone can normally withstand stresses in only one direction. Why is there this
difference and what structures account for this difference?
11.5
What are the functions of the four types of bone cells?
11.6
If the synovial fluid is not formed properly, there is the possibility for the cartilage at the ends
of the bone to come into contact with each other. How can synovial flow be re-established
and what would happen if it were not re-established?
11.7
Calculate the change in molecular volume of the synovial fluid if the formation rate of
synovial fluid by the synovial membrane is 6.5
g/hr/cm
2
and by the cartilage is 73 ng/
hr/cm
2
. Assume that the synovial membrane area is 15 mm
2
and that of the cartilage is
25 mm
2
. The degradation rate of the synovial fluid is 23 ng/hr, and the flux of synovial
fluid out of the membrane is 0.97
μ
μ
g/hr.
11.8
Calculate the restricted diffusion coefficient for proteoglycans within the synovial fluid if
the time rate of change of proteoglycans within synovial fluid is 0.095 mg/hr. The free
diffusion for proteoglycans in water is 1.25
E
7cm
2
/s. Assume that the degradation
rate for proteoglycans is negligible and that the formation rate for proteoglycans within
the synovial membrane and the cartilage is 2.2
g/hr/cm
2
and 31 ng/hr/cm
2
, respec-
tively. The area of the synovial membrane is 15 mm
2
and that of the cartilage is 25 mm
2
.
The permeability of this proteoglycan through the synovial membrane is 1.23
E
μ
6 cm/s,
and the concentration gradient for this proteoglycan is 0.07 mg/mL.
11.9
Consider a person that is standing on their tiptoes on one foot. The forces acting on this
joint are their weight (175 lb), the force of the muscle (F
M
) acting through the Achilles
FIGURE 11.7
Diagram of a foot for homework problem 11.9.
Adapted from Ozkaya
and Nordin (1999).
O
F
M
F
J
A
B
C
W
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