PATHOLOGY

Detailed explanation-1: -Vasoconstriction of pulmonary vessels causes an increase in both alveolar capillary pressure and vascular fluid shear stress. Flooding of pulmonary capillaries and increased capillary permeability occur. Fluid and inflammatory cells leak into the air sacs that are normally dry.

Detailed explanation-2: -Vasoconstriction increases pressure within a vein as it does in an artery, but in veins, the increased pressure increases flow. Recall that the pressure in the atria, into which the venous blood will flow, is very low, approaching zero for at least part of the relaxation phase of the cardiac cycle.

Detailed explanation-3: -Reflex venoconstriction is defined as a neurogenically induced contraction of the smooth muscle in the walls of veins; it causes a reduction in vascular capacity which is seen as a decrease in the volume of blood contained at the same pressure, an increase in the pressure at the same volume, or a combination of both.