#tract  a system of body parts that together serve some particular purpose
  supertype:  #system.body_part  a group of physiologically or anatomically related organs or parts; "the body has a system of organs for digestion"
  subtype:  #respiratory_tract__respiratorytract  the passages through which air enters and leaves the body
     subtype:  #lower_respiratory_tract__lowerrespiratorytract  the bronchi and lungs
     subtype:  #upper_respiratory_tract__upperrespiratorytract  the nose and throat and trachea
  subtype:  #urinary_tract__urinarytract  the organs and tubes involved in the production and excretion of urine

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