Historical Background
and
Book Contents
3
capillary bed.
Bypassing the
capillaries
are
the
arterio-venous
anastomoses, which
are now
known to perform the
function of
controlling blood flow.
German anatomist Henle discovered the smooth muscle cells in small
arteries in 1841. Thus, this provided the first evidence that smooth
muscle contributes to arterial contraction. But it is not until 1937 that
Zweifach showed that active contractility of the microvessels is confined
to those vessels with smooth muscle cells.
In the investigation of the microcirculation, credit was given to Hall,
an English physiologist, first to differentiate the
capillaries fi-om
arterioles.
The fact that capillaries transfer water and water-soluble
substances from the blood stream to surrounding tissues, was shown by
Starling and is now known as
the
Starling’s
hypothesis.
The
measurement of capillary blood pressure by cannulation was first
performed in 1930, by Landis, in the nail microvascular bed (Mayrovitz,
1998).
The ultra-structure of the microcirculation has now been
established from electron microscope studies.
French physiologist Claude Bernard in 1852 showed that stimulation
of sympathetic nerves induces vasoconstriction and the concept
of
controlling blood flow by vasomotor nerves.
Neural control of the
circulation is an important aspect of assessing vascular function.
Fascinated by anatomic structure of the vascular tree, as an art,
Leonard0 da Vinci (1452-1519) made many detailed drawings
of
the
constituent parts of the circulatory system. He apparently already knew
that both the contraction and resting periods are necessary for the heart to
function with a normal rhythm. His anatomic drawings of the heart and
the perfusing arteries are, to a large extent, amazingly accurate. This
includes drawings of the heart and the great vessels, together with the
main, anterior descending and circumflex coronary arteries and their
major branches.
Several drawings of the heart valves, demonstrating
how well the leaflets are arranged when the valves are closed, as well as
the detailed anatomic drawing of the neck arteries in man with its
branching morphology were also shown (Li, 2000). In these, both the
length and angle of branching arteries are incredibly accurate. Vesalius
(15 14-1564), an anatomist, later provided a detailed drawing of the entire
human vascular tree (Fig.
1.1.1).
