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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“But the doctrine of the Farm is merely this, that every man ought to stand in primary relations to the work of the world, ought to do it himself, and not to suffer the accident of his having a purse in his pocket, or his having been bred to some dishonorable and injurious craft, to sever him from those duties.”
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