Which of the following contributes to the formation of the outflow tracks?

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Outflow tract development comes from the conotruncal region of the heart tube, with the bulbus cordis playing the direct role in forming the proximal outflow tract, including the infundibulum that leads into the great arteries. As development progresses, the bulbus cordis and truncus arteriosus are partitioned by neural crest–derived tissue to create the aortic and pulmonary channels. This makes the bulbus cordis the structure most actively shaping the outflow tracks.

Endocardial cushions mainly drive atrioventricular septation and the membranous portion of the interventricular septum, not the outflow tract itself. The primitive atrium forms the atrial chambers, which are separate from the outflow tract formation. The truncus arteriosus contributes to the great arteries but is not the primary precursor for the initial outflow tract portion in the same direct way as the bulbus cordis.