6. Insect circulatory system

The insect circulatory system is responsible for transporting essential metabolites, carrying waste to the excretory system, and providing immunity against harmful organisms.

Insects possess a simple, open circulatory system. It consists of a dorsal vessel, which runs the entire length of the body. This vessel is divided into a posterior heart with intake valves called ostia and an anterior aorta.

The open body cavity in insects is known as the hemocoel, filled with insect blood called hemolymph. Unlike vertebrate blood, hemolymph does not transport oxygen and therefore lacks hemoglobin, giving it a different color.

Hemolymph is pumped forward by the heart through the aorta into the head, then flows back through the body within the open hemocoel. It re-enters the posterior heart through the ostial valves, continuously cycling. The heart ensures thorough mixing of the hemolymph.

Additional pulsatile hearts are located at the base of the antennae, legs, and wings, specifically pumping hemolymph into these appendages.