When the developing heart assumes its S-shaped form, the<unk>  lies ventral to the primitive ventricle.  Together, the<unk>  and the primitive ventricle give rise to the ventricle of the formed heart.
The adjacent walls of the<unk>  and ventricle approximate, fuse, and finally disappear, and the<unk>  now communicates freely with the right ventricle, while the junction of the<unk>  with the truncus arteriosus is brought directly ventral to and applied to the atrial canal.
By the upgrowth of the ventricular septum the<unk>  is in great measure separated from the left ventricle, but remains an integral part of the right ventricle, of which it forms the infundibulum.
Bulbus cordis
Malleus
Squama temporalis
Crista terminalis
Ganglion impar
Manubrium
Plexus
Pampiniform plexus