Red blood cell
Red blood cell
of smooth muscle in the arteriole
wall produces dilation, whereas (
contraction of the smooth muscle
causes constriction (
Dorsalis pedis a.
Posterior tibial a.
Sites where an arterial pulse is most easily detected.
stands for artery.)
Blood pressure increases
Some of the factors that inF
uence arterial blood
Arterial walls are elastic, so when the ventricles dis-
charge a surge of blood, arteries swell. Almost immediately,
the elastic tissues recoil, and the vessel walls press against
the blood inside. This action helps force the blood onward
against the peripheral resistance in arterioles and capillar-
ies. Recoiling of the arteries maintains blood pressure during
diastole. If there were no elasticity in the arterial walls, blood
pressure would fall to zero between ventricular contractions.
Elastic recoil also converts the intermittent ﬂ
ow of blood,
characteristic of the arterial system, into a more continuous
movement through the capillaries.
ı˘-te) of a ﬂ uid is a physical property
that derives from the ease with which its molecules flow
past one another. The greater the viscosity, the greater the
resistance to ﬂ
resistance by constricting these vessels. Blood tends to back
up into the arteries supplying the arterioles, and the arte-
rial pressure rises. Dilation of the arterioles has the opposite
effect—peripheral resistance lessens, and the arterial blood
pressure drops in response