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Internal surface (left atrium, anatomy)

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

The internal surface of the left atrium is notable for:

  • its generally smooth endocardial surface; this is the result of most of the left atrium originating embryologically from the pulmonary veins
  • the interatrial septum:
    • passes obliquely, posteriorly from right to left across the cavity of the chamber
    • often, a lunate depression is visible; this corresponds to the ostium secundum of the developing heart
  • the narrow aperture leading to the auricle; as with the right atrial auricle, musculi pectinati line its surface; however, the ridges are less well developed than in the right atrium
  • veins entering into the chamber:
    • pulmonary veins, typically two on each side entering in the superior part of the chamber; there are no valves at the intersection of each vein with the chamber
    • foramina venarum minimarum as in the right atrium
  • the atrioventricular orifice:
    • inferiorly and anteriorly within the chamber
    • smaller than the right atrioventricular orifice
    • associated with the mitral valve

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