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:
“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)
“When we consider how much climate contributes to the happiness of our condition, by the fine sensation it excites, and the productions it is the parent of, we have reason to value highly the accident of birth in such a one as that of Virginia.”
—Thomas Jefferson (1743–1826)