01:119:116 Lecture Notes - Lecture 24: Portal Vein, Superior Vena Cava, Gastrovascular Cavity
11 Oct 2016
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Document Summary
Animals need to exchange gasses with the surrounding environments. Diffusion is not efficient enough for most animals to transfer nutrients. Time it takes a substance to diffuse is proportional to the square of the distance. Two body plans have evolved to accommodate gas exchange. Animal has an opening that allows for almost all cells of body to contact environment. Only cells directly in contact with gastrovascular cavity have direct access to digested nutrients, but these animals are small enough that diffusion will work for their transport. Heart contraction pumps the hemolymph through the circulatory vessels into interconnected. In a closed circulatory system, a circulatory fluid called blood is confined to vessels and is distinct from the interstitial fluid. sinuses, spaces surrounding the organs. Within the sinuses, chemical exchange occurs between the. One or more hearts pump blood into large vessels that branch into smaller ones that infiltratethe organs. hemolymph and body cells.
