Vascular
Biology,
Structure and Function
015
-
m-
I
:
3
010-
e
m
3
005
-
0.00
-150
-100
-50
0
50
100
150
200
Transmural
Pressure
[mm
Hg]
O'Oo5r
29
-150
-100
-50
0
50
100
150
200
Transmural
Pressure
[mm
Hgl
Fig.
2.2.5:
Pressure
dependence of mechanical properties of arteries
is
demonstrated in
these figures.
A.
Lumen diameter increases with transmural pressure, following an
S-
shape.
B.
Area compliance plotted as a function of both positive and negative transmural
pressures. Compliance decreases with increasing pressure when the transmural pressure
is
positive and when the vessel is collapsing with negative transmural pressure.
From
Drzewiecki et
al.
(1997).
Along the arterial tree, longitudinally, we find that the number of
elastic laminae decreases with increasing distance from the aorta, but the
amount of smooth muscle increases and the wall thickness to radius ratio
increases.
The stiffness is thus increased.
This latter phenomenon
accounts for the large increase in pulse wave velocity (Chapter
4).
The
mechanical properties are largely influenced by the behavior of the
smooth muscle.
Its elastic properties and activation have attracted
considerable interests.
A
longitudinal section also reveals a helical
organization
of
the collagen fiber network.
It is this network that
contributes mostly to the anisotropic properties of the arterial wall.
