sentences: maintaining homeostasis requires respiration & the respiratory system performs respiration ->  respiration performed by the respiratory system is required for maintaining homeostasis  the lungs are a part of the respiratory system & the lungs are a part of the body of an animal used for breathing air ->  the respiratory system is used for breathing air  respiration performed by the respiratory system is required for maintaining homeostasis & the respiratory system is used for breathing air ->  breathing air performed by the respiratory system is required for maintaining homeostasis  breathing out is when animals exhale carbon dioxide from their lungs into the air & tightening muscles in the chest can be used to exhale ->  tightening of the muscles of the chest is used for exhaling carbon dioxide out of the lungs when breathing  tightening of the muscles of the chest is used for exhaling carbon dioxide out of the lungs when breathing & the muscular system contains muscles ->  tightening of the muscles of the chest performed by the muscular system is used for exhaling carbon dioxide out of the lungs when breathing  breathing air performed by the respiratory system is required for maintaining homeostasis & tightening of the muscles of the chest performed by the muscular system is used for exhaling carbon dioxide out of the lungs when breathing -> the muscular system tightens the muscles of the chest to help the respiratory system exhale carbon dioxide out of the lungs when breathing in order to maintain homeostasis