Question

当吸气时                                                                                                                                

        A．肋间肌和膈肌收缩                                  B．肋间肌和膈肌舒张

        C．膈肌顶部上升                                      D．肺内气压增大

 

Answer 1

【答案】

A

【解析】吸气时，膈顶部下降，膈肌和肋间肌收缩，胸廓容积扩大，肺内气压小于外界大气压。