Vascular Endothelium - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 564

BLOOD

Ca

Na

shear NOx shear

RTK GPCR

I I

Src G

VE cadherin

Shc

PECAM1

Grb2

K

FAK

Rho, Rac, Cdc42 PI3K

Shc

NO

cytoskeleton

ERK PKC

VEGFR2

PKB

PI3K

NF κ B

ET

EC

stretch

stretch

Ca

GPCR

NOx

pressure

ECM

SACC RTK

I

I

Src

G

FAK vasodilation

PLC

Rho, Rac, Cdc42

PKC

MAPK

vasoconstriction

cytoskeleton

SMC

Fig. 9.7 Effects of blood pressure characterized by its large magnitude on the vessel wall cells and
of three-dimensional shear of much smaller magnitude than the applied pressure, but with large
spatial gradients, on the wetted surface of endothelial cells. Both forces undergo large-amplitude
oscillations during the cardiac cycle. Directional changes can also occur (flow separation and flow
reversal during the diastole). I: integrin.

The endothelium provides a link between blood flow and vessel responses, in
particular the vessel caliber. Multiple kinds of mechanical stresses and various types
of mechanical environments are associated with flow patterns and unsteadiness.
The vessel wall is sheared by the moving blood particles on the one hand and
stretched and compressed by the pressure applied by blood. Mechanical stresses
applied to the endothelial wetted surface are indeed normal (mostly pressure)
and tangential (shear). Wall friction fluctuates in magnitude and in direction at a
given location and from point to point. Pressure and tensile reactions also undergo
quasi-periodic fluctuations. The stresses applied by the blood continuum 149

are

149 When the flow scale is much greater than the circulating cell size, the blood can be considered
as a continuum with given apparent physical properties, which depend on the microstructure of the
concentrated suspension. The microstructure depends on the local stress field.