This paper outlines the macroscopic anatomy and physiology of the heart, linking the micro and macroscopic structure of cardiac muscle fibre to its function during contraction and dilatation. The properties of cardiac muscle cells and the process of contraction at a cellular level are described. The macroscopic structure of the myocardium is further explained as one muscle band wound into a double twist. This helps to elucidate the muscle architecture and structure of the ventricles. Ventricular dynamics are also described as the twisting and untwisting of this muscle band to produce shortening and lengthening. Myocardial perfusion and causes of disease are discussed. Coronary artery disease and its effect on contractility is then described and ways of measuring contractility are introduced
