Dorsal Vessel

This single blood vessel, a long slender tube, extends forward along the midline of the back of the abdomen from about the sixth abdominal segment through the thorax and then into the head. In the thorax, the vessel, now called the aorta, loops down between the flight muscles that power the wings. In the head, the aorta, now close to the esophagus, passes under the brain to open into the hemocoel beneath the brain. The abdominal portion of this tube is the heart, and the posterior end of the heart is closed. Even though circulation usually requires a beating heart and assistance from accessory pumps, much hemolymph circulates whenever the skeletal muscles contract. Muscles associated with movements of the pharynx and alimentary canal indirectly propel hemolymph.

0 0

Post a comment