<prompt> The ductus aeriosus closes anatomically within:-Immediately after bih7 days after bih4-6 weeks after bih10 - 21 days after bih  <response>: - Anatomical closure of ductus aeriosus occurs within 10 to 21 days after bih. Occurs by proliferation of its intima cells - Functional closure of ductus aeriosus occurs immediately after bih by smooth muscle contraction which occurs as a result of increase in oxygen saturation. 