Fig. 8. Anatomy of the heart and its incurrent and excurrent openings in D. melanogaster. (A) Light micrograph of the entire heart, ventral view. Ostia 2, 3 and 4 (O2, O3, O4) are clearly visible through the transparent dorsal diaphragm. Fat body (FB) and pericardial cells (PC) cover the posterior part of the heart. DLM, dorso-longitudinal flight muscles attached to the mesophragma (Ph II). (B–E) SEMs. (B) Ventral view of the entire heart. The dorsal diaphragm (DD) with its longitudinal muscles is visible, covering the ventral surface of the heart. The excurrent opening (EO) is visible between the pair of caudal suspending muscles. AM, alary muscles. (C) Longitudinal cut of anterior heart chamber with first ostium (O1). Anterior (Ant OC) and posterior valve cells (Post OC) protrude into the heart lumen. (D) Third ostium with closed valve lips. (E) Caudal end of the heart with excurrent opening, suspending muscles severed to expose the relaxed opening and the connective tissue strands (CT).