This textbook explores the fundamental qualitative and quantitative aspects of human physiology. It approaches biological and physiological processes and phenomena from a quantitative perspective, revealing how physiological problems can be mathematically formulated starting from simple laws of physics. The book addresses a broad range of topics, including: the statics and dynamics of circulation; muscle and sarcomere force-length and force-velocity relations, together with their mechanisms and functional consequences; subdivisions and meaning of the heat produced by muscle; locomotion, statics and dynamics of respiration; diffusion of gases and acid base equilibrium; phonation; general functions of the kidney and of the different sections of the nephron; changes in clearance with a substance's plasmatic concentration; pH regulation and the kidney; Donnan's equilibrium and its consequences; and the Nernst equation. The book offers the ideal learning resource for students of human physiology courses in medicine and biomedicine, as well as biomedical engineering and biophysics graduate students. An elementary grasp of mathematics and physics is sufficient to understand the content.