In the developing heart, the atria initially communicate with each other by an opening between the free edge of the septum primum and the AV cushions, known as the primary interatrial foramen or ostium primum (interatrial foramen primum), below the free margin of the septum.
Read more about Primary Interatrial Foramen: Closing of Ostium Primum, Clinical Significance
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“Anyone who has obeyed nature by transmitting a piece of gossip experiences the explosive relief that accompanies the satisfying of a primary need.”
—Primo Levi (1919–1987)