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:
“It is closing time in the gardens of the West and from now on an artist will be judged only by the resonance of his solitude or the quality of his despair.”
—Cyril Connolly (1903–1974)
“Some say that ever ‘gainst that season comes
Wherein our Saviour’s birth is celebrated,
The 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 tale nor witch hath power to charm,
So hallow’d and so gracious is the time.”
—William Shakespeare (1564–1616)