WordNet records no synonym and no antonym for elastic tissue. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
connective tissue consisting chiefly of elastic fibers found in the dermis of the skin and in the walls of veins and arteries and in some tendons and ligaments
Synonyms, antonyms and the broader and narrower relations for elastic tissue come from Princeton University’s WordNet. Full sources and licences.