Structural, functional and energetic characteristics of the blood circulation. The concept of hydraulic filtering of vessels, energy requirements and distribution of blood flow, blood circulation and synthesis of ATP. The distribution of blood flow, consumption of O2 and arterial-venous difference. Blood flow regulation. Flow and flow speed. Resistance to blood flow. Functional relationship between the blood network and the electrical circuit: resistance and impedance. Determinants of systemic vascular resistance. The blood viscosity, the length of the vessel, the area of the transverse section of the vessel. The Poiseuille law, laminar flow and turbulent flow. Blood pressure. Functional role of blood pressure. Energy: the primary cause of the flow of blood, the forms of energy of the blood and the energetic gradients in hemodynamics: nature and characteristics: the Bernoulli theorem. Gravitational potential energy and blood pressure in humans. The continuity equation and the Venturi principle in hemodynamics. Hemodynamic aspects of atheroma and aneurysm: biophysical analysis. The Starling hypothesis.