Closing During Birth
To provide proper blood flow as a a newborn, the foramen secundum and foramen ovale must close when birth occurs. Since the lungs now require a significant amount of blood flow, the vessels going to and from the lungs undergo dilation. While the pulmonary artery and pulmonary veins are dilating, the umbilical artery and umbilical vein are severed due to the cutting of the umbilical cord, or the funiculus umbilicalis. This combination results in a reversal of pressure differences between the atria and the septum primum is permanently forced against the septum secundum. This holds true even during atrial diastole, when the pressure is significantly less than atrial systole.
Read more about this topic: Foramen Secundum
Famous quotes containing the words closing and/or birth:
“Although sleep pressed upon my closing eyelids, and the moon, on her horses, blushed in the middle of the sky, nevertheless I could not leave off watching your play; there was too much fire in your two voices.”
—Propertius Sextus (c. 50–16 B.C.)
“Marriage is like a war. There are moments of chivalry and gallantry that attend the victorious advances and strategic retreats, the birth or death of children, the momentary conquest of loneliness, the sacrifice that ennobles him who makes it. But mostly there are the long dull sieges, the waiting, the terror and boredom. Women understand this better than men; they are better able to survive attrition.”
—Helen Hayes (1900–1993)