Definition of absolute, relative and transmural pressures. Manometers. Mechanical energy of a fluid. Statics of circulation: effect of height, acceleration and immersion in water on blood pressure and distribution within the body. Dynamics of circulation. Laminar motion: derivation of the parabolic profile of blood velocity within a vessel, the law of Poiseuille and its consequences. Axial accumulation of red cells: effect of vessel dimensions and the Fahraeus-Lindqvist effect. Flowmeter. Turbulent motion: derivation of the critical velocity and of the Reynolds Number. Incidence of kinetic energy in circulation: downstream pressure, side pressure and end pressure in different parts of the circulation. The sphygmic wave. Measurement of blood pressure. Organization of systemic and pulmonary circulation. Equilibrium conditions of blood vessels: definition of tension and the Law of Laplace. Elastic, active and mixed tensions in vessels walls. Critical closing pressure. The capillaries. Function of capillaries. Factors affecting production of the interstitial fluid and edema. Venous circle. Pulmonary circle from top to bottom of lung zones in the erect position: waterfall effect. Coronary flow: effect of heart beats frequency. Fetal circle.