part of continuous with adult dorsal vessel adult heart fly_anatomy.ontology The caudal, pulsatile region of the adult dorsal vessel. It extends from the first to the sixth abdominal segment, lying just below the surface of the cuticle, and has four pairs of ostia (Curtis et al., 1999). It is supported along the midline of the body by a series of paired alary muscles, suspensory fibrils and a rudimentary dorsal diaphragm (Miller, 1950). The caudal end is closed and is attached to the 6th abdominal tergite and to the dorsal wall of the rectal sac. The wall of the heart consists of a single muscular layer containing circular striated fibers and scattered lateral nuclei. On the ventral side, an outer layer or longitudinal muscles extends the whole length except for the caudal end. UBERON:0015230 FBbt:00003154 abdominal tergite 6 multi-tissue structure adult rectal sac