Historical Background and Book Contents
7
(Noordergraaf,
1969).
Incorporating the elastic properties and geometry
of the blood vessel, Moens (1878) and Korteweg (1878) separately
developed what is now known as the Moens-Korteweg formula for the
pulse wave velocity:
(1.1
.l)
where
E
is, appropriately at the time, defined as the Young’s modulus of
elasticity of the blood vessel, h and r are the wall thickness and inner
radius of the uniform cylindrical vessel, respectively, and
p
is the density
of blood. Pulse propagation velocity is seen related to the mechanical
and geometrical properties of the blood vessel.
1.2 Importance
of
the Vascular System
In terms of the dynamics
of
the vascular system, the function of the heart
is
to provide energy and perfuse organ vascular beds.
For the heart to
accomplish this efficiently, the vascular system plays a central role
as
the
distributing conduits. Both the distributing arteries and the peripheral
vascular beds present the load to the pumping heart.
Peripheral
resistance has been popularly viewed in the clinical setting as the
vascular load to the heart. This applies mainly to steady flow conditions.
This description is naturally inadequate, because of the pulsatile nature
of blood flow which remains throughout the microcirculation. Pulsatility
implies that there is an oscillatory or pulsatile contribution to the
vascular load to the heart. The importance of pulsatility, though still
under much debate,
is
nevertheless necessary in terms of synchronicity
and efficiency.
The vascular system provides
a
seamless illustration of an efficient
transport system. This can be seen from the function of, for instances, the
coronary circulation in perfsuing the heart, the renal circulation in
perfusing the kidneys, the cerebral circulation in perfusing the brain and
the pulmonary circulation in perfusing the lungs.
By
virtue of the
distributing arterial trees, oxygen, humoral agents, and nutrients be
transported to the vital parts of the body, and at the same time, removal
of biological waste materials is also accomplished.
