These wastes are either excreted via the lungs in the case of carbon dioxide, or the kidneys in the case of various products of nitrogen metabolism.
(These wastes; are; either excreted via the lungs in the case of carbon dioxide, or the kidneys in the case of various products of nitrogen metabolism) (These wastes; excreted; )
These wastes These wastes
are excreted
either excreted via the lungs in the case of carbon dioxide, or the kidneys in the case of various products of nitrogen metabolism