The fossa ovalis is an oval depression on the right atrial side of the interatrial septum. It marks the site of the foramen ovale, the opening that let blood pass from the right to the left atrium before birth. Its raised margin is called the limbus.
| Location | Interatrial septum, on the posterior wall of the right atrium, above and to the left of the opening of the inferior vena cava. |
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| Parts |
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In the fetus the foramen ovale shunts oxygenated blood from the inferior vena cava straight into the left atrium. After birth, rising left atrial pressure pushes the flap shut, and it normally fuses to leave the fossa.
In about a quarter of adults the flap does not seal completely, leaving a patent foramen ovale. The thin floor of the fossa is the usual target for transseptal puncture to reach the left atrium during catheter procedures. Secundum atrial septal defects lie within the fossa ovalis region.
Incomplete fusion of the flap, allowing intermittent right-to-left passage of blood. It is linked to some cryptogenic strokes, migraine with aura and decompression illness in divers.
A true hole in the region of the fossa ovalis, the most common type of atrial septal defect. Many can be closed with a catheter device.
A floppy, bulging floor of the fossa that swings between the atria. It often accompanies a patent foramen ovale and may raise embolic risk.
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