<P> The oblique vein of the left atrium is partly responsible for venous drainage; it derives from the embryonic left superior vena cava . </P> <P> During embryogenesis at about two weeks, a primitive atrium begins to be formed . It begins as one chamber which over the following two weeks becomes divided by the septum primum into the left atrium and the right atrium . The interatrial septum has an opening in the right atrium, the foramen ovale which provides access to the left atrium; this connects the two chambers, which is essential for fetal blood circulation . At birth, when the first breath is taken fetal blood flow is reversed to travel through the lungs . The foramen ovale is no longer needed and it closes to leave a depression (the fossa ovalis) in the atrial wall . </P> <P> In some cases, the foramen ovale fails to close . This abnormality is present in approximately 25% of the general population . This is known as a patent foramen ovale, an atrial septal defect . It is mostly unproblematic, although it can be associated with paradoxical embolization and stroke . </P> <P> Within the fetal right atrium, blood from the inferior vena cava and the superior vena cava flow in separate streams to different locations in the heart, and this has been reported to occur through the Coandă effect . Atriums were previously named' auricles' </P>

What is the function of the right and left auricles