1. به نام خدا Blood Circulation 2
Dr. Radmanesh

2. Distensibility distensibility
Vascular distensibility:
Increase in volume/Increase in pressure* Original volume
distensibility
is related to a vessel’s ability to distend with increase in pressure

3. Difference in distensibility of the arteries and the veins.
the walls of the arteries are far stronger than those of the veins.
the arteries, on average, are about eight times less distensible than the veins.

4. In the pulmonary circulation
the pulmonary arteries under pressures about one sixth of those in the systemic arterial
their distensibilities are about six times the distensibility of systemic arteries

5. Compliance Definition of vascular compliance (capacitance) Compliance
VC = increase in volume / increase in pressure
Or VC = VD X original volume
Compliance and distensibility are quite different
Compliance
is related to the total amount of blood that can be stored in a vessel with increasing pressure

6. Compliance and distensibility are quite different
Veins are 8 times more distensible,
it has a volume about 3 times as great
Veins 24 times more compliant than arteries
(8*3 = 24)

7. Volume - Pressure Curves
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8. (stress-relaxation) of vessels
Delayed compliance
(stress-relaxation) of vessels
Effect on the intravascular pressure of injecting a volume of blood into a venous segment and later removing the excess blood, demonstrating the principle of delayed compliance.
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9. Pressure Pulse Systolic pressure – diastolic pressure
PP is proportional to stroke volume / AC
AC: compliance of the arterial tree .

11. Abnormal Pressure Pulse Contours
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14. Veins and their Functions

15. Right Atrial Pressure
(Central Venous Pressure)
(-3 to-5, 20-30mmHg)
regulated by a balance between
(1) the tendency for blood to flow from the peripheral veins into the right atrium.
(2) the ability of the heart to pump blood out of the right atrium and ventricle into the lungs

16. Factors that increase venous return
Increased blood volume
Increased large venous tone
Dilation of arterioles
(decrease resistance)

17. Venous Resistance
the veins from the arms are compressed by their sharp angulations over the first rib.
the pressure in the neck veins
veins coursing through the abdomen

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19. Peripheral venous pressure
Effect of Intra-abdominal pressure
When increased, it increases venous pressure in the legs
Intra-abdominal pressure may increase:
Due to pregnancy
Abdominal tumors
Ascites (excessive fluid in the peritoneal cavity)

20. Effect of gravitational pressure
Venous pressure above the heart is less than 0 mm Hg
Venous pressure below the heart is greater than 0 mm Hg
the pressure in the veins of the feet is about +90 mm Hg

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22. Veins and their Functions
Valves ensure one-way movement of blood
Muscle pump
Thoracic pump

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