 Dear students, in this topic we shall discuss the local control of microcirculation. Many compounds influence capillary blood flow locally within a tissue. These substances include endothelium produced compounds, inflammatory mediators, and many metabolites and many other substances like hormones. First we shall discuss the endothelium produced compounds. Vascular endothelium releases nitric oxide, endothelene, and prostacycline. They affect vascular smooth muscles and capillary blood flow. Nitric oxide causes relaxation of vascular smooth muscle and acts as basodilator. Endothelene causes vasoconstriction, while prostacycline causes vasodilation and also act as anticoagulant. Now we shall discuss the role of inflammatory mediators in the control of micro circulation. From Voxin A which is formed by platelets causes vasoconstriction locally. Histamine which is released from the connective tissue and white blood cells in injured tissues causes vasodilation. That is it increases blood flow in the injured tissue. The plasma kinins for example bradykinin are potent vasodilators in damaged tissues. Now we shall discuss some other substances. The hormone norepinephrine which is released from sympathetic nerves acts as vasoconstrictor. Angiotensin which is formed in the lungs circulates in the blood and acts as local vasoconstrictor where required. Serotonin which is found in high concentration in the gut and blood platelets acts as vasoconstrictor or vasodilator. The role that depends on viva scular bed and on its concentration.