Transcript Physiological bases of hemodymanic

Physiological bases of
hemodinamic
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hemodinamic
– is a chapter of physiology of blood circulation
system, which is study causes, conditions and
mechanisms of blood moving in cardio-vascular
system.
Types of blood moving
Fluid stream in the pipe is
described by formula:
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Q= (P1-P2)/R, where
Q - fluid volume,
P1 - pressure in the beginning of the pipe,
P2 - pressure in the end of the pipe,
R - peripheral resistance of the pipe.
Peripheral resistance of vessels
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Peripheral resistance in vessels according to
Poiseuille's formula depends on length of
vessels (l), viscosity of blood (η) and crosssection of vessel (r):
R= 8lŋ/πr.
Paradoxes of blood flow.
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In capillaries blood flow resistance is lower because of such
mechanism. In capillaries blood cells move one after another,
dividing only by plasma, which decreases friction between
blood cells and capillary wall. On other side, capillaries are
shorter, than arterioles, which caused lower blood flow
resistance too.
Viscosity of blood is also important for resistance of vessels. It
depends on quantity of blood cells, protein rate in plasma,
especially globulins and fibrinogen. Considerable increase of
blood viscosity may cause lower blood returning to the heart
and than disorders of blood circulation.
In large arteries centralization of blood flow is observed.
Blood cells moves in the central part of blood stream, and
plasma is peripheral. Instead increase of blood viscosity in
arterioles is caused by higher friction between cells and vessels
wall.
Functional types of vessels
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- Elastic (damping) vessels. Large arteries belong to this
group. The main function of these vessels is to turn ejection of
blood into continuous blood flow. It is possible due to elastic
properties of its wall;
- Resistive vessels are arterioles, precapillary sphincters and
venuls. These vessels may regulate the blood flow in
capillaries by changing their tonus;
- Exchange vessels are capillaries. Their walls due to the
special structure permit exchange of materials between blood
and tissues;
-Capacitive vessels are veins. To sure one-way direction of
blood flow veins have valves if lying below the heart. Veins
contain 75-80 % of circulating blood. Veins of skin and
abdominal cavity may function as depot of blood.
Functional types of vessels
Functional peculiarities of vessels
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1. Еlasticity
2. Соntractility
3. Тоne
4. Permability
Blood pressure
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Transversal pressure - is difference between pressure
inside the vessel and squeeze of it from the tissues.
Hydrostatic pressure is corresponding to weight of all
blood in vessel when it has vertical position.
For vessels of head and neck this pressure decreases
towards the heart. For vessels of limbs it has outward
direction. That is why hydrodynamic pressure in
vessels over heart is decreased due to hydrostatical
pressure. Below heart hydrodynamic pressure is
increased, because it is summarized with
hydrodynamic pressure.
Linear velocity of blood flow
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Blood flow also is characterized by
linear velocity of blood circulation:
V=Q/πr2, where
V - linear velocity,
Q - blood volume,
r - radius of vessel.
Аrterial pressure
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Аrterial pressure – pressure, which have the blood
in the arterial vessels of human body.
Factors:
– cardiac
– vessels
– blood
Kinds of arterial pressure
1. systolic (less than 139 мм Hg)
2. diastolic (less than 89 мм HG)
3. puls pressure (PP=SP-DP).
 4. Middle dynamical pressure (PP/3+DP)
Determine of arterial pressure
Arterial pressure
Notion
Arterial pressure
Systolic, мм Diastolic, мм
Hg
Hg
Optimal
< 120
< 80
Normal
< 130
<85
130-139
85-89
>140
>90
140-149
90-94
Higher normal
Hipertension
Mesure hyprtension
Arterial pulse
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60-90 per minute
Sphigmogram
а-аnacrota; b-catacrota;
і-іncisura; с-dicrota.
Properties of arterial pulse
1. Pulse
rate per minute – 75±15.
2. Pulse rhythmisity