On the other hand current molecular approaches have actually stimulated the revival of two of the old proposals first that the notochord is a novelty that arose in the chordates and second that it is derived from a homologous structure the axochord that was present in annelid like ancestors. Introduction the notochord is an embryonic midline structure common to all members of the phylum chordata in higher vertebrates the notochord exists transiently and has at least two important functions. Notochord structure the notochord is made of a number of different structural molecules including glycoproteins and resembles cartilage in many ways when you cut across the notochord and view the cross section under a microscope it appears as a series on concentric rings. Synopsis although it is the defining organ of chordates the notochord is perhaps the least understood of vertebrate organs because it is usually considered a transient structure only present in early embryonic development
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