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Septum secundum
Interior of dorsal half of heart of human embryo of about thirty-five days. (Septum secundum visible at center top.)
Same heart as above, opened on right side. (Septum secundum visible in dark area at center top.)
Gray's	subject #135 512
Carnegie stage	14
Days	33
Gives rise to	atrial septum

The septum secundum, semilunar in shape, grows downward from the upper wall of the atrium immediately to the right of the primary septum and ostium secundum.

Shortly after birth it fuses with the primary septum, and by this means the foramen ovale is closed, but sometimes the fusion is incomplete and the upper part of the foramen remains patent.

The limbus fossae ovalis denotes the free margin of the septum secundum.

[edit] External links

• Embryology at Temple Heart98/heart97a/sld037
• cardev-039 — Embryology at UNC
• Overview at edu.mt
• MedEd at Loyola GrossAnatomy/thorax0/Heart_Development/Atria.html

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