#respiratory_organ__respiratoryorgan  any organ involved in the process of respiration
  supertype:  internal_organ__viscus  a main organ that is situated inside the body
  part of:  respiratory_system
  subtype:  branchia__gill  respiratory organ of aquatic animals that breathe oxygen dissolved in water
     subtype:  ctenidium  comb-like respiratory structure serving as the gill of certain mollusks
     subtype:  ceras__cera  one of the often brightly colored and branching hornlike structures on the back of the nudibranch (and other related mollusks) that serve as gills
     subtype:  external_gill  occurs in some mollusks and in tadpoles and other immature amphibians
  subtype:  lung  either of two saclike respiratory organs in the chest of vertebrates; serves to remove carbon dioxide and provide oxygen to the blood
  subtype:  book_lung  organ in many arachnids containing many thin folds of membrane resembling the leaves of a book

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