血管生理

Hemodynamics Blood flow:

flow velocity is related to total cross-sectional area (sum of total cross sections of all capillaries Laminar flow Turbulent flow

Blood flow through vessels depends on the pressure gradient and vascular

F=P/R F:flow rate of blood through a vessel P: pressure gradient R: resistance of blood vessels

Poiseuille’s law

Arterial system As a conduit for blood between the heart

and capillaries as a preeusure reservoir for forcing blood

into the small-diameter arterioles dampen oscillations in pressure and flow control distribution of blood to different

capillary network

Blood pressure Measurement direct method indirect method systolic pressure diastolic pressure pulse pressure

Direct measurement

TransducerBP amplifier

Recording system

A/D converter

PC

printer

Effect of gravity and body position

Arteriole The major resistance vessels control of distribution of

blood flow

pressure drop from 97 mmHg to 37 mmHg

Arteriolar tone Vasoconstriction↑

Myogenic activity ↑oxygen ↓carbon dioxide and other metabolites ↑sympathetic stimulation, ADH, AII. Cold

Vasodition ↓ myogenic activity ↓ Oxygen ↑ CO2 and other metabolites ↑adenosine release ↓ sympathetic stimum, histamine release, heat endothelial-derived relaxing factor (EDRF) such as NO

Venous system Blood conduit for flowing

through blood reservoir

Factors influencing venous return

Sleleta-muscle pump

respiratory pump

cardiac pump

Capillaries and microcirculation

Lymphatic system