Venoussystem

TomHorváthM.D.Ph.D.

Topics

1. Structuralaspects2. Hemodynamicfunctions3. Pressure-diameterbehavior4. Centralvenouspressure&vascularfunction

Thecirculatorysystem

pulmonaryveins

systemicveins

Pressuredistribution

Distribution of total blood volume

veins64

arteries13

pulmonarycirculation

9

capillaries7

heart7

Totalbloodvolume~5.5Liter

Venousbloodvolume~3.52Liter

Hemodynamicfunctionsoftheveins

• Conduitfunction– channelbloodtowardtheheart

• Flowrectification(anti-gravitationalfunctions)– venousvalves– musclepump– abdominalpump

• Capacityfunction– bloodstorage(60-70%)

• spleen~150ml• liver~200-300ml• abdominallargeveins~300ml

Structuralaspects– arteriesvs.veins

Structuralaspects– arteriesvs.veinsII.

Arteriesandveinsunderpressure

COMPLIANCE:DV/DP

DISTENSIBILITY:DV/(DP× V0)

Flowrectification– valves– I.

Flowrectification– musclepump– II.

Flowrectification– thoraco-abdominalpump– III.

INSPIRATIONbloodflowsrapidlytowardthechest

EXPIRATIONbloodflowsslowstowardthechest

Centralvenouspressure

• Visafronte(fromthefront~RA)

• Visatergo(fromtheback~LV)

ThevascularfunctioncurveI.

Conceptof“deadpressure”a.k.a.meancirculatorypressure

• Q=5l/min• Pa =102mmHg• Pv =2mmHg• Ph =Pa - Pv =100mmHg• TPR=Ph/Q=20mmHgmin/l• C=DV/DP• Ca/Cv =1/19

ThevascularfunctioncurveII.

ThevascularfunctioncurveIII.