Why Does Decreasing Arteriolar Resistance Lead to Oedema?

[briton]

can someone help me understand why decreasing arteriolar resistance will (increase filtration and..) result in oedema?
I thought that decreasing resistance decreases pressure so filtration decreases


but, all I've got in my notes is that constricting arterioles increases the resistance and downstream blood (capillaries) loose pressure and in a book it says high precapillary resistance shields the capillary from arterial pressure. I don't understand how this is..

 

[quasi426]

can someone help me understand why decreasing arteriolar resistance will (increase filtration and..) result in oedema?
I thought that decreasing resistance decreases pressure so filtration decreases

Arteriolar have smooth muscle that allow them to contract and alter the resistance of blood flow as resistance is inversely proportional to the 4th power radius (Poiselle's Laminar Flow eqn.) When arteriolar's decrease their resistance via relaxation of surrounding smooth muscle, the capillaries will receive blood with an increase flow rate. The key idea here is that filtration and absorbtion occurs in the capillaries and not in the arteriolar blood vessels. Applying the Pressure = flow x resistance equation here shows that the increase flow rate leads to an increased capillary hydrostatic pressure and leads to increased filtration. Hope that helps, I curtailed the explanation on account that you are a current mini expert in the making.

 

[Ouabache]

Here is a related thread that may provide additional insight.