ABSTRACT
This chapter focuses on the physical nature of the hydrodynamic problems associated with blood flow and fluid transfer. It discusses the physiological mechanisms from a macroscopic point of view, and avoids, wherever possible, the considerations of various processes that take place on the level of cells. The chapter describes the phenomenological behavior of the cardiovascular system and on the description of its physical properties. A survey of the literature will reveal two different approaches to the control process in the circulatory system. One, used mostly by engineers and system analysts, attributes the control characteristics to the larger blood vessels. The other, used mostly by biophysicists and biochemists, assigned to the capillaries and the single cells the same control properties. The chapter explores the essential elements of the blood circulation control system. The physiological role of the pulmonary circulation is entirely different from the systemic circulation, and therefore there are marked differences between them.
