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.)
“Some say that ever ‘gainst that season comes
Wherein our Saviour’s birth is celebrated,
This bird of dawning singeth all night long,
And then they say no spirit dare stir abroad,
The nights are wholesome, then no planets strike,
No fairy takes, nor witch hath power to charm,
So hallowed, and so gracious, is that time.”
—William Shakespeare (1564–1616)