open vascular system
Quick Summary
An open vascular system is found in many invertebrates, where fluid, called hemolymph, bathes organs directly in body cavities called sinuses or a hemocoel. This differs from a closed system, like that in vertebrates, where fluid circulates exclusively within vessels.12
In malacostracans, a type of crustacean, the circulatory system is open but more complex than in other crustaceans. They possess a tubular heart located dorsally, which pumps hemolymph through arteries to the head, gills, and appendages. Veins are absent, and hemolymph returns to the heart through sinuses. Insects also have an open circulatory system where hemolymph transports nutrients and waste but is not involved in respiration. The hemolymph contains cells called hemocytes that aid in defense.345
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