septum secundum


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Related to septum secundum: foramen ovale, foramen secundum

sep·tum se·cun·'dum

the second of two major septal structures involved in the partitioning of the atrium, developing later than the septum primum and located to the right of it; like the septum primum, it is crescentic, but its tips are directed toward the sinus venosus, and it is more heavily muscular; it remains an incomplete partition until after birth, with its unclosed area constituting the foramen ovale.