We present simulations for the human circulatory system using a closed-loop network incorporating arterial, venous, and portal venous systems, along with the heart-pulmonary circulation and micro-circulation in capillaries. This system considers the conservation of blood volume flux and pressure distribution over the entire network, including 62 arteries, 42 veins, 27 micro-vasculatures, and the heart-pulmonary circulation. Cerebral arteries containing the circle of Willis are also considered to examine the complex flow distribution patterns there. Blood flows in large blood vessels are simulated using one-dimensional models, whereas zero-dimensional lumped-parameter models are utilized to simulate blood flow in vascular subsystems corresponding to peripheral arteries and organs. Transmission conditions at bifurcations and confluences are solved using Riemann invariants. Our simulations aim at reproducing and understanding mechanisms for flow and pressure distributions under widely diverse physiological and pathological conditions, such as heart failure scenarios and different types of flow patterns in cerebral arteries.