Overview

Abstract

The circulatory system, consisting of the heart and arterial, venous, and capillary blood vessels, delivers oxygen and nutrients to all organs and transports metabolites to sites of further metabolization and excretion. To execute this central role, the heart continuously pumps the blood through the vasculature(see chapter “Overview” under part “Blood vessels”). Although the heart is a single organ, in terms of function, it represents two pumps working in series.Whereas the left heart generates high pressure (basal level 120 mmHg) to supply all organs (except the lung) with oxygenated blood, the right heart enables blood flow through the pulmonary vasculatureby generating a low-pressure gradient (basal level 20 mmHg). Left and right hearts show a similar gross anatomy: Both consist of an atrium and a ventricle, which are separated by a septum. Due to the differences in workload, themuscle mass of the left ventricle exceeds that of the right one. To achiev directed blood flow, inlet valves (i.e., mitral and tricuspid valves) separate the atria from theventricles, and outlet valves (aortic and pulmonary valves) separate the ventricles from the aorta and pulmonary artery (Fig. 1).