Invertebrate animals like insects, arthropods, and most mollusks have an open circulatory system, blood bathes the internal organs directly.
Contraction of the hearts pumps hemolymph through vessels, which open into the interconnected system of sinuses. When the hearts relax, they draw hemolymph through pores, which are equipped with valves, that close when the heart contracts.
Animals like annelids (earthworms), some mollusks (squids and octopuses), and vertebrates have closed circulatory systems, the blood is confined within blood vessels. Chambered hearts with valves and relatively thick muscular walls are less commonly found in invertebrates but occur in some mollusks, especially cephalopods (octopus and squid). The direction of flow is controlled by valves between the chambers.
Lymph is transported along the system of lymphatic vessels by muscle contractions, and valves prevent lymph from flowing backward.

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