BIOL 103 Chapter Notes - Chapter 45: Ventral Nerve Cord, Gastrovascular Cavity, Extracellular Fluid
27 Sep 2013
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Content: gastrovascular cavities, open circulatory systems, closed circulatory systems. In cnidarians (jellyfish and hydras), the surrounding water not only contains the nutrients and o2 to sustain life, it also serves the functions of the animals" circulatory system. Water enters the gastrovascular cavity, a body cavity with a single opening to the outside. Food is digested in the cavity and absorbed by body cells and wastes excreted into cavity. In some cnidarians, cilia line opening of gastrovascular cavity propel water through and muscular stretching and relaxing of the body wall move water throughout cavity. These body muscles act like a heart because the pulsing of these muscles are regulated by nerves: open circulatory systems. In an open circulatory system, vessels open into animal"s body cavity so fluid in vessels and interstitial fluid mingle in one large mixed compartment: hemolymph is pumped by several muscular hearts, nutrients and wastes are exchanged by diffusion.
