2. Rule : NO GRADEINT… NO FLOW.
Even the pressure was so high
• pressure gradient is the main force (main
factor).
• Other Factors that regulate the flow:
1- Diameter of the blood vessel:طردية Q=
2- Length of the blood vessel.عكسية
3- Viscosity of the blood.عكسية
100 100
ΔP
R
Ohm’s law
Polycythemia,Anemia
3.
4. For example: if you have a vessel of a radius of 1,
and the flow is 1 … if you increase the radius to 2
(increased 100%) the flow will increase (2 ^ 4) = 16.
5. • The cardiac output is distributed in our bodies
unequally; this depends on the tissue need of
blood. When the tissue is at rest it needs less
blood, when the tissue is undergoing
metabolism it needs more blood. This is the
function of arteries, capillaries and veins.
6. Differences between arteries and
veins:
• Muscle thickness of the blood vessel.
• Arteries (pressure reservoirs) high pressure
• Veins (blood reservoirs) low pressure
%65 of the blood
in our bodies is
present in the
veins.
7. Distensibility:the capability of vessels to stretch, dilate, or
swell by pressure from within.
• Veins: (more distensible 8 times than arteries)
due to thinner wall than arteries.
A drop of 1-2 liters in the volume of blood inside veins will
not cause a great critical effect on the venous blood
pressure, whereas blood loss from arteries, even if it was
not great in volume, will cause a significant fall in arterial
blood pressure with a high risk of patient’s death.
8. Vascular Compliance (or Vascular
Capacitance)
• total quantity of blood that can be stored in a
given portion of the circulation for each mmHg
Veins accommodate three times the volume of blood
in arteries
The arterial system accommodates around 750 ml of
blood , the venous system accommodates around
2750-3000 ml of blood
9. • A small change in the pressure inside veins significantly
alters the volume of blood within it.
• - A small change in the volume of blood within arteries
significantly alters the pressure inside it.
10. Critical Closing Pressure
• Critical closing pressure is defined as the
pressure at which the vessel collapses.
• seen with increased sympathetic stimulation
as it can cause severe vasoconstriction
• happens because vessels are surrounded by
tissues which apply external pressure on them
leading to their closure.
• The arterial critical closing pressure is
normally around 20mmHg.
11. Physiological relations in
Hemodynamics:
• 1- Pressure: (systole and diastole)
The pressure in the left ventricle rises to the
maximum during systole and drops to the
minimum during diastole . The maximum
systolic pressure is 110-130 mmHg and the
minimum pressure is 0 mmHg.
The pressure in the aorta will never drop to 0 as
in the left ventricle, because before the
pressure in the aorta decreases from 80
mmHg the next heart beat(systole) will occur.
12. • If there is no systole (heart beat) the pressure
in the aorta will reduce and the patient will
lose consciousness due to the lack of blood
reaching the brain.
• من الدم ضغط قياس ناخذ احنا جذي منaorta not from
left ventricle due to diastolyic pressure=0
15. Laminar flow and Turbulent flow:
• Laminar flow: (normally in our body)
• fluid flows near a wall, it will have friction with that
wall.(resistance that will cause the velocity of the
blood near the wall to decrease.
• The maximum velocity of the blood is found in the
center of the vessel which has no friction.
You don’t hear
any sound
during this
flow.
16. turbulent flow: (ATH,stenosis,…..)
• squeezing this vessel (constriction), cause the
blood to flow in different directions.
• You will hear sounds during this flow like
murmurs.(Anemic patients)
17. • What causes the tendency to develop
turbulent flow?
• - Diameter of the vessel (constriction).
• - Velocity of the blood: higher velocity higher
tendency, this is related to something called
Reynold’s number.
• Reynold’s Number: = vpD/u > 400
• measures the tendency to develop turbulent
flow. It depends on the velocity, diameter,
viscosity and the density.
density viscosity
there is a possibility to
develop turbulent flow
Reynold number reaches 4000 sever aortic stenosis.
18. Where does the maximum resistance
occur?
• Arterioles
• Capillaries :so there is no resistance at all
• Veins : There is resistance
• The peripheral resistance is nearly to 1 (0.93), we don’t
use a unit for peripheral resistance we just say it’s 1.
• pressure gradient=93
• Flow (cardiac output) = volume / time = (6*1000)/60 =
100 milliliter / sec
19. 3- Velocity :distance/time.
• the bigger the surface area, the less velocity,
which is found in the capillaries for better
exchange (very huge surface area). The less
surface area, the higher the velocity which is
found in the aorta.
20. 4-flow:volume/time.
• identical everywhere
• The same amount of volume will go to all the
areas in the body; the cardiac output will go to
aorta, to the large arteries, to the small
arteries and arterioles. BUT the velocity is
different in these areas.
21. Measuring Systolic and Diastolic
Pressures
• directly measured by inserting a cannula into
an artery and connecting a manometer to it,
but this method is inconvenient and can be
uncomfortable or painful to the patient.
• indirect means, usually by the auscultatory
method using a sphygmomanometer.
22. • inflatable rubber cuff connected to an air valve
and a mercury manometer (due to its high
density)
• the cuff is placed at the level of the heart on the
brachial artery slightly above the cubital fossa,
and then the cuff is inflated.
23. • The cuff applies a pressure on brachial artery
causing the blood flow to stop when the
pressure in the cuff is higher than the pressure
in the artery.
• the next step : gradually and slowly decrease
the pressure in the cuff to permit the blood to
flow
24. tracking the pulse by:
• Palpation method; feeling the pulse by pressing on the
radial artery. When there is no flow there will be no
pulse. The blood pressure at which the first pulse is felt
is the systolic pressure. The diastolic pressure cannot be
measured by palpation.
• Auscultation method; using a stethoscope
• The pressure exerted by the cuff creates a turbulent
flow of blood in the artery and the pressure at which
blood starts flowing (indicated by an audible sound) is
the systolic pressure.
• The pressure at which the blood flow becomes laminar
and inaudible is the diastolic pressure.
25. Korotkoff sounds
• The sounds heard during the measurement of
blood pressure are called Korotkoff sounds.
• neither related to the sounds of the heart, nor
related to the ejection of blood by heart, nor
related to the valves.
26. Heart Sounds
• the closure of atrioventricular valves(tricuspid
and mitral valves) creates the first heart sound
(S1), closure of the semilunar valves
(pulmonary and aortic valves) creates the
second heart sound (S2).
• second heart sound (S2) is louder than the
first heart sound(S1). because the diameters
of semilunar valves are smaller than the
diameters of atrioventricular valves,
27. Cardiac Murmur
• A stenosis in the cardiac valve results in a turbulent blood
flow through the valve, which in turn creates an abnormal
sound called cardiac murmur. two types of cardiac murmur:
• 1- Systolic cardiac murmur: Occurs between S1-S2
• due to aortic valve stenosis or mitral valve incompetence
results in ejection murmur, which sounds similar to “shh” /
ʃ/.
• 2-The diastolic murmur Occurs between S2-S1
• due aortic valve incompetence is called rumbling murmur,
which sounds similar to “rrrrr”.
• The diastolic murmur due to mitral stenosis produces a
similar sound to the ejection murmur.
