30
Dynamics
of
the Vascular System
2.3
Functional Properties
of
Blood
Blood is the principal vehicle and medium that serves to provide
nutrients and remove waste products throughout the complex multi-
cellular constituents
of
the body organs.
It consists
of
a plasma fluid
with a number of formed elements.
2.3.1 Blood Plasma and Blood Gas
Blood plasma is about 90-95% water and contains numerous dissolved
materials that include proteins, lipids, carbohydrates,
electrolytes,
hormones and pigments. It is
the proteins that
dominant
the
characteristics of the plasma, which has a specific gravity
(SG)
of
plasma, which
is
about 1.028.
.
These are albumin, globulin and
fibrinogen. The principal concentration by weight through fractionation
electrophoresis shows that albumin which has the lowest molecular
weight
(69,000)
exhibits the highest concentration of some
55%,
followed by globulin (80,000-200,000) of about 38% and
largest
molecular weighted fibrinogen (350,000-400,000) of just
7%.
These proteins play an important functional role in viscosity, osmotic
pressure and suspension characteristics
of
the plasma. Gases, such as
oxygen and carbon dioxide are dissolved in the blood plasma. Their
partial pressures can be derived from gas laws. We know that for an ideal
gas, the pressure, volume and temperature are related by the gas law:
PV
=
nkT
(2.3.1)
where
P
is the pressure,
V
is the volume, n is the number of gas
molecules,
k
is Boltzmann's constant, and T is absolute temperature in
Kelvin. The concentration,
C,,
is normally expressed in terms of moles
per unit volume,
n
c,
=-
"4V
(2.3.2)
where
NA
is the Avogadro's number.
Substitute for the universal gas
constant
R=kNA
we have
