part of continuous with adult tracheal dorsal trunk adult prothoracic dorsal tracheal branch adult metathoracic dorsal tracheal branch adult cervical trachea adult tracheal air sac parenteric air sac Elongated air sac of the adult thorax. It is a continuation of the abdominal dorsal trunk. It flanks the digestive tube in the thorax and becomes the cervical trachea in the neck region. It anastomoses anteriorly with the lateral system of the same side through a wide medial extension of the propleural sac, and posteriorly through a short connective near the posterior thoracic spiracle. The two parenteric sacs are connected by a short, straight dorsal commissure in the prothorax and a longer curved commissure under the mesophragma, both passing above the alimentary canal. fly_anatomy.ontology FBbt:00003111 propleural air sac