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:
“Our two eyes do not make our lot better; one serves us to see the good things, the other the evils of life. A lot of people have the bad habit of closing the first, and very few close the second.”
—Voltaire [François Marie Arouet] (1694–1778)
“They do not live in the world,
Are not in time and space.
From birth to death hurled
No word do they have, not one
To plant a foot upon,
Were never in any place.”
—Edwin Muir (1887–1959)