Morphometric examination of the sinoatrial region of the heart

A quantitative electron-microscopic examination was performed of the tissue structure of the working and conducting myocardium of the sinoatrial region of rat heart. The volume fractions of intracellular components of specialized myocytes of the sinus node and of internodal conduction tracts, as well as of working cardiomyocytes of the right atrium were measured. The study presents a characteristic of cell dimensions of myocytes of the given region. Principles of a universal classification of cardiomyocytes making it possible to automatically allot heart cells to individual structurally different classes are discussed.