>> AS SOON AS THE CORD IS CLAMPED,
THE DUCTUS VENOSUS CEASES TO CARRY
BLOOD TO THE HEART, AND IT
BEGINS TO CONSTRICT WITHIN
THE FIRST FEW HOURS 
OR DAYS OF LIFE.
THE VERY FIRST THING THAT
HAPPENS WHEN THE FETUS IS BORN
IS IT TAKES ITS FIRST BREATH,
THE LUNGS EXPAND,
AND SO THE RESISTANCE,
OR PRESSURE, IN THE LUNGS DROP,
AND THAT PROMOTES BLOOD 
FLOW INTO THE LUNG ITSELF.
THE DUCTUS ARTERIOSUS BEGINS 
TO CONSTRICT AND IS TYPICALLY
FULLY CLOSED WITHIN 
24 TO 48 HOURS OF LIFE.
AND BLOOD IS NOW THEN FULLY
DIRECTED INTO THE LUNG.
AS THE BLOOD RETURNS TO THE LEFT
SIDE OF THE HEART AFTER
TRAVERSING THE PULMONARY
CIRCULATION AND PICKING UP
OXYGEN, THE PRESSURE IN THE LEFT
ATRIUM RISES JUST A BIT.
AND THE TRAP DOOR 
OF THE FORAMEN OVALE,
WHICH WAS OPENED BEFORE BIRTH,
NOW BEGINS TO CLOSE,
USUALLY WITHIN THE FIRST FEW
DAYS OF LIFE.
