First PreNatal Scan (5 wks, 4 days)

Mellise • ~BFP August 2016!~ 👶🏻💙 (used pre-seed.softcups.opks) Pregnant with #2 Due Jan,11,2019
I was wondering, Does the yolk sac turn into the placenta? &
Does the fetus develop inside the yolk sac or outside?