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A quantitative ultrastructural analysis was made of tissue components in the conducting myocardium of the sinus node and in the working perinodal myocardium of the right atrium from the sinoauricular region of the heart in 10 subjects who had suddenly died of coronary heart disease or cerebral hemorphage in the presence of hypertensive disease. Volumetric densities were estimated in myocytes, connective tissue, capillaries, and nerves; diameters of conducting and working myocytes were also measured in the sinoauricular region of the heart. The data of the analysis were compared with those of estimation of tissue components in the sinoauricular region in sudden extracardiac death. The paper discusses whether the findings are important for understanding the significance of tissue homeostasis maintenance in the sinoauricular region of the human heart.
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