Cardiovascular System: Part II

Abstract

This chapter gives an overview of blood circulation, then focuses on regional blood flow to a number of organs, and ends with a description of the microcirculation. It begins with venous return and blood volume. Most blood volume is contained within the venous system, and the chapter describes several mechanisms that allow for this volume of blood to be returned to the right heart. Next it describes the various means by which the blood circulation and volume are controlled. The chapter devotes considerable time describing the central, peripheral, and hormonal regulation of circulation and blood volume. Next, regional blood flow is described. Blood flow in different regions of the body is usually autoregulated, and variably controlled by the autonomic nervous system, and various humoral agents. The final section describes the mechanism by which blood flow in the microcirculation delivers nutrients, and removes wastes from the tissue by diffusion. Also described are the regulation of the microcirculation by pre and post capillary sphincters, and the effect of viscosity. This review contains 5 figures, and 40 references.  Keywords: venous return, vascular compliance, venous capacitance, vasomotor center, hypothalamic-pituitary-adrenal axis (HPA), microcirculation, regional blood flow, mixed venous oxygen saturation