part of tracheal lateral trunk anterior branch primordium Anteriorly directed ventral branch of the tracheal primordium that gives rise to the anterior portion of the lateral trunk in each tracheal metamere. It arises as the anterior side of a bifurcation at the ventral end of the tracheal primordium during stage 12. It fuses with posterior branch of the lateral trunk of the next segment to its anterior during stage 14 or 15. fly_anatomy.ontology FBbt:00000234 LTa tracheal branch primordium tracheal lateral trunk primordium primary segmental tracheal branch primordium