Histology
The sinoatrial node is submyocardial at the lateral aspect of the junction of the superior vena cava and right atrium. Its deep aspect abuts cardiac myocytes belonging to the right atrium. Its superficial aspect is covered by adipose tissue. The SA node fibres vaguely resemble cardiac myocytes; however, they are measurably thinner, more tortuous and stain less intensely (on H&E) than cardiac myocytes.
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