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:
“And if the stage-dark head rehearse
The fifth act of the closing night,
Why, cut it off, piece after piece,
And throw the tough cortex away....”
—Allen Tate (1899–1979)
“Thirty-five is a very attractive age. London society is full of women of the highest birth who have, of their own free choice, remained thirty-five for years.”
—Oscar Wilde (1854–1900)