Circulatory System
Insects do not have veins or arteries, thought they have circulatory systems. When blood is moved throughout the body without, the organism has an open circulatory system. Hemolymph (insect blood) flows freely through the body and makes direct contact with organs and tissues.
A single blood vessel runs along the back of the insect, from the head to the abdomen. The vessel divides into chambers and functions as the insect’s heart. Holes in the heart wall, called ostia, allow hemolymph to enter the chambers from the body cavity. Muscle contractions push hemolymph from one chamber to the next, moving it toward the thorax and head. In the thorax, the blood vessel is not chambered. Like an aorta, the vessel directs the flow of hemolymph to the head.
A single blood vessel runs along the back of the insect, from the head to the abdomen. The vessel divides into chambers and functions as the insect’s heart. Holes in the heart wall, called ostia, allow hemolymph to enter the chambers from the body cavity. Muscle contractions push hemolymph from one chamber to the next, moving it toward the thorax and head. In the thorax, the blood vessel is not chambered. Like an aorta, the vessel directs the flow of hemolymph to the head.