At Birth
At birth, when the infant breathes for the first time, there is a decrease in the resistance in the pulmonary vasculature, which causes the pressure in the left atrium to increase relative to the pressure in the right atrium. This leads to the closure of the foramen ovale, which is then referred to as the fossa ovalis. Additionally, the increase in the concentration of oxygen in the blood leads to a decrease in prostaglandins, causing closure of the ductus arteriosus. These closures prevent blood from bypassing pulmonary circulation, and therefore allow the neonate's blood to become oxygenated in the newly operational lungs.
Read more about this topic: Fetal Circulation
Famous quotes containing the word birth:
“The warped, distorted frame we have put around every Negro child from birth is around every white child also. Each is on a different side of the frame but each is pinioned there. And ... what cruelly shapes and cripples the personality of one is as cruelly shaping and crippling the personality of the other.”
—Lillian Smith (1897–1966)
“A small boy puts his hand on the wall, and looks down intently as he wriggles his toes. The birth of thought?”
—Mason Cooley (b. 1927)