The Conduction System
The sinoatrial (SA) node, within which the pacemaker normally resides, contains nodal cells, transitional cells, and intercalated clear cells arranged into a well-defined mass. The location and extent of the SA node varies slightly between mammalian species. In the rabbit, cat, mouse, rat, guinea-pig and monkey, the SA node is located in the wall of the superior vena cava (SVC), above or extending down to the crista terminalis (Viragh and Challice 1973 a; Viragh and Porte 1973 a; LEV and Thaemert 1973; Tranum-Jensen 1976). The SA node of the guinea-pig (Anderson 1972a), golden hamster (Walls 1942), and rabbit (James 1967) occupies the full thickness of the atrial wall. In most human hearts the SA node occupies a lateral position at the junction of the SVC and right atrium, but can also be draped over the junction of the SVC and the right atrial appendage (Fig. 29) (Anderson et al. 1979).
KeywordsPurkinje Cell Transitional Cell Superior Vena Cava Conduction System Nodal Cell
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