Heart and Vessels

Abstract

The heart lies like an oblique cone within the chest, surrounded by the right and left lungs. The base of the heart projects dorsocranially to the right, and the apex ventrocranially to the left. Under physiological conditions about two-thirds of the heart lies in the left side of the chest and one-third in the right. The size of the heart is quite similar to that of the individual’s closed fist (total weight about 5 g/kg [~ 250–350 g]). The longitudinal septum divides the heart into left and right halves, which are each subdivided into an atrium and a chamber (ventricle). Four cardiac valves act as “check valves”, and under physiological conditions they allow blood flow only in an antegrade direction. A distinction is made between the tricuspid and mitral valve (i.e. atrioventricular valves) located between the respective atrium and ventricle (in-flow tract) and the pulmonary and aortic valves (i.e. semilunar valves) located between the right chamber and pulmonary circulation and the left chamber and systemic circulation, respectively (outflow tract).

The blood supply of the heart muscle (myocardium) occurs via two separate coronary vessels: the right coronary artery (RCA) and the left coronary artery (LCA). The latter is divided into two main branches: the left anterior descending artery (LAD) and the left circumflex artery. On the back of the heart, the two systems communicate.

The shape, size, and position of the heart are closely linked, and cardiac and extracardiac factors cause a large number of variants, knowledge of which is essential to avoid false judgments.