What type of circulatory system do insects have?

Insects possess an open circulatory system, which is characterized by having a heart that pumps blood (hemolymph) into a series of vessels that eventually empty into cavities called hemocoels. These cavities surround the internal organs, allowing the hemolymph to directly bathe the tissues, facilitating the exchange of gases and nutrients. This system differs fundamentally from a closed circulatory system, where blood remains confined to vessels.

The open circulatory system in insects is efficient for their body size and metabolic needs, providing ample distribution of nutrients while also allowing waste products to be carried away. Additionally, oxygen is delivered to the tissues through a separate system of tracheae, which is unique to insects and further reduces reliance on the circulatory system for gas exchange.

In contrast, the mixed and systemic circulatory systems are not applicable to insects, as these terms describe arrangements found in other organisms, primarily vertebrates. Thus, the classification of insects having an open circulatory system is accurate and crucial for understanding their physiology and ecological roles.