Transcript Lecture 28. Physiology of venous system

Physiology of venous system
Blood flow in veins
Blood flows through the blood
vessels, including the veins, primarily,
because of the pumping action of the
heart, although venous flow is aided
by the heartbeat, the increase in the
negative intrathoracic pressure during
each inspiration, and contractions of
skeletal muscles that compress the
veins (muscle pump).
Morpho-functional properties of
venous system
Veins are the vessels, which are carry
out blood from organs, tissues to
heart in right atrium. Only pulmonary
vein carry out blood from lungs in left
atrium. There are superficial (skin)
and deep veins. They are very
stretching and have a low elasticity.
Valves are present in veins. Plexus
venosus are depo of blood. Blood
moving in veins under gravity.
Mechanism of regulation
Difference of pressure in venous
system is a cause of blood moving.
From the place of high pressure blood
moving to the place of low pressure.
Negative pressure in chest is a cause
of blood moving. Contraction of
skeletal muscles, diaphragm pump,
peristaltic movement of veins walls
are the causes of moving.
Venous pressure
Venous pressure is pressure of blood,
which are circulated in veins. Venous
pressure in healthy person is from 50
to 100 mm H2O. Increase of venous
pressure in physiological condition
may be in the action of physical
activity. Determine of venous
pressure is called phlebotonometry
and give for doctors information about
activity of right atrium.
Phlebography
а – atria wave –contraction of
right atrium
с – passing of carotid artery
pulse on vein
х – systole of ventricles
v – ventricular – filling of
atrium by blood
y – passing of blood in right
atria
Speed of blood stream
Speed of vein blood stream depend
on diameter of vessels. In venuls
speed of blood moving is lower. In
veins of middle diameter it 7-14 cm/s,
in big veins the speed is near 20
cm/s. In big veins speed of blood
moving depend on breathing and
heartbeat.
Venous pulse
Venous pulse is a moving of walls of
big veins, which are depend on
heartbeat. The cause of it stop of
blood flow from vein to heart during
atrium systole. At these time pressure
in it increase. Methods of
investigation of venous pulse are
phlebography.
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