True statement about ductus arteriosus is:

d. May cause a machinery murmur by its patency.(Ref: Nelson's 20/e p 497, Ghai 8/e p 413)Closure of ductus arteriosusPhysiological closure: occurs almost immediately after birth by contraction of muscular wall, mediated by bradykininAnatomic closure: occurs by proliferation of intima in 10-21 days; After obliteration, it forms ligamentum arteriosum. Note: Murmur due to PDA is classically referred to as a continuous machinery murmur.