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ARTERIAL & VENOUSSYSTEM

Dr. MRS. Chhaya Saraf

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LEARNING ISSUES

Understand the importance of arterialdistension and recoil

Describe the mechanisms of peripheral

arterial pulsationsArterial system & functions

Venous system & functions

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Anatomy

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WALLS OFBLOODVESSELS

Circular Smooth Muscle

Vaso-constriction/dilation

Elastin and collagen

Strengthens, Anchors

EndotheliumMinimize friction

Sympathetic stimulation(alpha receptors) Noradrenalinecauses vasoconstrictionSympathetic inhibition VasodilatationVasomotor tone-Even at rest sympathetic tone is there

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WINDKESSELEFFECT

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VASCULAR DISTENSIBILITY

P

Dilatation

Increased Blood flow

Distensibility allows blood vessels to accommodatepulsatile output & also smooth flow to tissues

Veins are 6-10 times more distensible

Fractional increase in volume per 1 mmHgpressure rise

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VASCULAR COMPLIANCE/CAPACITANCE

Total quantity of blood stored per 1 mmHgpressure rise

Compliance = Distensibility x volume

In veins compliance is 24 times more thanarteries (8x3)

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VOLUME PRESSURE CURVE

Increased sympathetic tone

increases pressure

Helpsin shifting blood e.g.hemorrhage

Small pressure changeafter large volume change

More pressure changeafter small volume change

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DELAYED COMPLIANCE-STRESS RELAXATION

Transfusion

Hemorrhage

Increased volume initially increases the pressure but

later on it comes to normal due to stretch

Stress relaxation of muscle

Readjustmentof muscle

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VENOUS SYSTEM

Main features Compliant Compressible

Extremity veins have

Valves Mean peripheral venous

pressure4-6 mmHg

Central Venous

Pressure(RAP)~ 0-4 mmHg Cardiac pumping VR

Increased RAP openscollapsed veins

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PERIPHERAL VENOUS PRESSURE

Venoconstriction by sympathetic stimulationmaintains the circulation & shifts a blood

Specific reservoirs Spleen

Liver

Large abdominal veins

Venous plexus beneath the skin

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Role of gravity

For every 13.6 mm distancethere is 1 mm Hg pressureincrease

It is seen in veins as well asarteries so arterial pressure inlegs is 100+90=190mmHg

HYDROSTATIC PRESSURE

AND VENOUS PRESSURE

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SKELETAL MUSCLE PUMP VENOUS PUMP

Incompetence & destruction of valves - varicose veins

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NORMAL ARTERIAL PRESSUREPULSATIONSATAORTICROOT

Pressure pulsations reduces tozero in capillaries d/to

distensibility & resistance inarteries

Dicrotic notch& wave

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DETERMINANTSOF PULSE PRESSURE

PULSEPRESSURE = STROKEVOLUMECOMPLIANCE(DISTENSIBILITY)

Systolic pressure

Diastolic pressure

Pulse pressure

In old age due to non

compliant arteries PP isincreased

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ABNORMAL PRESSURE PULSE WAVE

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Damping duringpropagation

PRESSUREPULSE PROPAGATION

pulse wave is not seenin capillaries.

Last curves show decreasein intensity due to changein Resistance &

Compliance of peripheralvessels

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MAIN STUDY MATERIALGUYTON 15THCHAPTER

Thank You