respiratory system

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Across
  1. 3. The airway that leads from the larynx to the bronchi and it is also called a windpipe
  2. 4. a pair of organs in the rib-cage
Down
  1. 1. It plays a major role in breathing, as its contraction increases the volume of the thorax and so inflates the lungs.
  2. 2. It is naturally present in air and is absorbed by plants in photosynthesis.