Structures or particles seen with the electron microscope. SYN: fine structure.
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ul·tra·struc·ture 'əl-trə-.strək-chər n biological structure and esp. fine structure (as of a cell) not visible through a light microscope
ul·tra·struc·tur·al .əl-trə-'strək-chə-rəl, -'strək-shrəl adj
ul·tra·struc·tur·al·ly -ē adv
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ul·tra·struc·ture (ulґtrə-struk″chər) the arrangement of the smallest elements making up a body; the structure beyond the resolution power of the light microscope, i.e., the structure visible only under the ultramicroscope and electron microscope. Called also fine structure.Medical dictionary. 2011.