Physiology is defined as the study of functions of various systems and different organs of the body. Physiology is of different types namely, Human Physiology, Animal Physiology, and Plant Physiology. Human Physiology and Animal Physiology are very much interrelated. Knowledge of Human Physiology is essential to understand the other sciences like Biochemistry, Pharmacology, Pathology, Medicine, Dentistry etc. However, it is worthwhile to have a brief knowledge of the anatomy of different systems and various organs to understand the principles of Human Physiology. The basic physiological functions include provision of oxygen and nutrients, removal of metabolites and other waste products, maintenance of blood pressure and body temperature, hunger and thirst, locomotor functions, special sensory functions, reproduction and the higher intellectual functions like learning and memory. All these functions are interrelated to each other and only after attaining the basic understanding a dentist can diagnose the disease. The purpose of this subject is to provide the dental student a comprehensive discussion of the wide variety of functions and systems of human body.