continuous with adult tracheal section adult tracheal dorsal trunk fly_anatomy.ontology Longitudinal tracheal branch of the adult, dorsal to the lateral trunk. It begins anteriorly as a backwards continuation of the first spiracular trachea. It joins the lateral trunk immediately behind the first thoracic spiracle. The dorsal trunk is very broad in diameter and sac-like (forming the parenteric air sac) until reaching the region of the fifth pair of spiracles. It then narrows, extending until abdominal segment 8. In the abdomen, it is connected to the lateral trunk in each segment by a long transverse connective. At the level of the second pair of spiracles, these connectives are much shorter and stouter. The right and left abdominal dorsal trunks of each segment are connected by a transverse dorsal commissure, or dorsal anastomose. FBbt:00003039 UBERON:6003039 adult tracheal transverse connective adult dorsal tracheal branch tracheal branch