英语翻译certain messenger molecules fight damage to the lungs from noxious air by telling the muscle cells encircling the lungs' airway to contract.This partially seals off the lungs.An asthma attack occurs when the messenger molecules are activated unnecessarily,in response to harmless things like pollen.

英语翻译
certain messenger molecules fight damage to the lungs from noxious air by telling the muscle cells encircling the lungs' airway to contract.This partially seals off the lungs.An asthma attack occurs when the messenger molecules are activated unnecessarily,in response to harmless things like pollen.