BIO 2135 Lecture Notes - Lecture 8: Clitellum, Anatomical Terms Of Location, Polychaete
12 Oct 2017
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Document Summary
Setal hairs (bristles) made out of chitin (beta-chitin) Annelids insert more segments between the anus segment and the peristomium. Youngest segments are added to the end of the organism (opposite of proglottid segments) Each segment is it"s own coelomic cavity separated from each other by a septum (made out of mesoderm) Thought to be a monophyletic event for a long time. In beta chitin the bres are arranged in the same direction in the bundle. Alpha chitin bres are arranged in opposite ways (hence there is an interlocking between gaps and chains hence they are locked very tight together and you get lots of ionic interaction making the structure extremely strong) Alpha chitin is used in all other animals that are not arthropods that use chitin. Beta chitin is used in arthropods ( beta chitin bres still interlock however not as tightly as alpha chitin bres hence it is weaker)
