During inflammation transudate and exudate is formed by vessels. I would like to make sure if it comes from arterioles, venules, or both, and the reason why.
exsudates almost exclusively come from the capillary compartment. If you think about the structure of the vessels, this appears logical.
The capillary compartment :
- has vessels only several microns thick
- has only the endothelial and basal lamina layers
- spans an enormous surface, far greater than arterioles or venules
So when the fenestrations and tight junctions of the capillaries are impaired, serum directly passes into the extracellular medium. A good example of that would be advanced anaphylactic shock. In this situation, the general inflammatory state causes a loss of endothelial integrity. Adrenaline given in such a state will have an inotropic and chronotropic effect on the heart, will cause vasoconstriction, but will also act to restore endothelial integrity. This last element is the main reason why allergic people carry an epinephrine syringe at all times.