MICROANATOMY

Detailed explanation-1: -Prostacyclin produces vasodilation, and thromboxane A2 causes vasoconstriction.

Detailed explanation-2: -Serotonin is transported by platelets and released upon activation. This induces constriction of injured blood vessels and enhances platelet aggregation to minimize blood loss.

Detailed explanation-3: -Vasoconstriction is primarily mediated by endothelin-1, a potent vasoconstrictor, which is synthesized by the damaged endothelium. Damaged endothelium exposes sub-endothelial collagen, von Willebrand factor (vWF), releases ATP, and inflammatory mediators.

Detailed explanation-4: -Serotonin appears to have a therapeutic effect on the postirradiation coagulation defect in that it decreases the prolonged heparin clotting time.