Development of the Aorta and Pulmonary Artery:
(From Cardiovascular Embryology, http://www.indiana.edu/~anat550/cvanim/index.html)
Heart Tube Development
Animation of the fusion of two endocardial tubes into a single primitive heart tube:
Aortic Arch Development
Aortic arch vessels develop from the 5th through 7th week:
And another view:
Atrial Septal Development
Embryology of the intra-atrial septum: