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Open and closed circulatory systems Year 11: Biology http://intranet.cbhslewisham.nsw.edu.au:82/science/concepta.asp?conID=13&resource=1 Retrieved 4 June 2011 • Outcome: compare the open and closed circulatory systems using one vertebrate and one invertebrate The circulatory systems of invertebrates • Invertebrates such as insects have a heart • The heart of a young snail, which has a thin shell, can sometimes be seen by holding the snail up to the light and looking up from below Insects circulatory • Invertebrates have an open circulatory system • Vertebrates have a closed circulatory system • The blood in a closed circulatory system remains within the tubes and materials diffuse in and out of the blood through the walls of tiny tubes called capillaries. • The circulatory systems in invertebrates is an open system • Invertebrates blood is pumped at low pressure directly into the main body cavity where it slowly flows about the cells • The blood is collected by open vessels like drains, which carry the blood back to the heart like drains • This inefficient circulatory system limits the size of invertebrates • Large vertebrates require a more efficient system to overcome their low surface area to volume ratio • In insects, the open circulatory system is supplemented with another separate open system of gas exchange • Insects have a series of small holes (spiracles), which open into a network of tubes called tracheae. • These tracheae distribute oxygen to body cells and carry away oxygen • This network relies on diffusion to move gases through them • Unlike vertebrates, which transport wastes, nutrients and gases in insects occurs through two systems • In vertebrates, nutrients, oxygen, CO2 and other wastes are transported by the circulatory system. Questions • 1. Name three animals that would have a closed circulatory system • 2. Name three animals that would have an open circulatory system • 3. Vertebrates can grow much larger than insects, explain why this is so in terms of their circulatory capacity