人生来就有一道道天然的生理屏障。胎儿时期,胎盘将母子相隔,使二者血液不相混合,并为胎儿提供氧气、营养及抗病因子,故称之“胎盘屏障”。大脑是人体最重要的器官之一,除有坚硬的颅骨保护外,脑细胞周围有一层结构复杂的基膜,它可以阻止某些毒物、药物、微生物进入脑组织内,这就是“血脑屏障”。而皮肤、血液、 People have a natural physiological barrier. Fetal period, the mother and child separated from the placenta, so that the two blood are not mixed, and to provide oxygen to the fetus, nutrition and anti-factor, so called “placental barrier.” The brain is one of the most important organs of the human body. In addition to its hard skull protection, there is a complex basement membrane around the brain cells that prevents certain poisons, drugs and microbes from entering the brain. This is the “blood-brain barrier ”. The skin, blood,