physiological barrier

例句：

1. 1. The immune system is a natural barrier against disease.
   免疫系统是对抗疾病的自然屏障。
2. 2. The new drug has shown promise as a potential barrier to cancer treatment.
   这种新药显示出成为癌症治疗潜在障碍的潜力。
3. 3. The researchers found that the bacteria had developed a physiological barrier to prevent penetration.
   研究人员发现，细菌已经发展出了一种生理屏障来防止穿透。