▁m esent ery ▁of ▁the ▁for eg ut ▁in ▁the ▁developed ▁human ▁being ▁and ▁other ▁m amm als . ▁ ▁Orig ins ▁ ▁The ▁sept um ▁trans vers um ▁originally ▁ar ises ▁as ▁the ▁most ▁c ran ial ▁part ▁of ▁the ▁mes en ch yme ▁on ▁day ▁ 2 2 . ▁During ▁c ran i oca ud al ▁fol ding ▁it ▁assumes ▁a ▁position ▁c ran ial ▁to ▁the ▁developing ▁heart ▁at ▁the ▁level ▁of ▁the ▁cer v ical ▁verte bra e . ▁During ▁subsequent ▁weeks ▁the ▁d ors al ▁end ▁of ▁the ▁emb ry o ▁grows ▁much ▁faster ▁than ▁its ▁vent ral ▁counter part ▁resulting ▁in ▁an ▁apparent ▁descent ▁of ▁the ▁vent r ally ▁located ▁sept um ▁trans vers um . ▁At ▁week ▁ 8 , ▁it ▁can ▁be ▁found ▁at ▁the ▁level ▁of ▁the ▁thor ac ic ▁verte bra e . ▁ ▁N erve ▁supply ▁After ▁successful ▁c ran i oca ud al ▁fol ding ▁the ▁sept um ▁trans vers um ▁pick s ▁up ▁inner v ation ▁from ▁the ▁adjacent ▁vent ral ▁r ami ▁of ▁sp inal ▁n erves ▁C 3 , ▁C 4 ▁and ▁C 5 , ▁thus ▁forming ▁the ▁prec ursor ▁of ▁the ▁phr en ic ▁n erve . ▁During ▁the ▁descent ▁of ▁the ▁sept um , ▁the ▁phr en ic ▁n erve ▁is ▁carried ▁along ▁and ▁assumes ▁its ▁desc ending ▁path way . ▁ ▁During ▁emb ry onic ▁development ▁of ▁the ▁thor ac ic ▁dia ph rag m , ▁my ob last ▁cells ▁from ▁the ▁sept um ▁in