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. 2018 Sep;10(Suppl 24):S2837–S2847. doi: 10.21037/jtd.2018.02.18

Figure 1.

Figure 1

Septation of the common atrial chamber. (A) The primitive atrial chamber opens to the developing ventricles through the atrioventricular (AV) canal. The right and left venous valves mark the border between the sinus venosus and the primitive atrium. The developing pulmonary veins enters the atrium at the pulmonary pit; (B) as the septum primum extends toward the atrioventricular canal, its upper portion breaks down to form the ostium secundum; (C) immediately to the right of the septum primum, the atrial wall folds to form the septum secundum. The inferior ends of the right and left venous valve fuse with tissues of the septum primum and spina vestibuli (Figure adapted from Ho SY. Embryology and anatomy of the atrial septum. In: Transseptal Catheterization and Interventions. Thakur R, Natale A, editors; Cardiotext 2010, Minnesota USA. Pages 11–26).