How is blood flow regulated in systemic circulation?

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Blood flow in systemic circulation is regulated primarily by changes in the diameter of arterioles, the small arteries that control blood entering capillary networks. When arterioles widen (vasodilation), blood flow increases; when they narrow (vasoconstriction), blood flow decreases. This allows the body to direct more blood to organs and tissues that need it most, such as the digestive system after a meal or skeletal muscles during exercise.