Bacteria, fungi, and viruses can enter our gut through the food we eat. Fortunately, the epithelial cells that line our intestines serve as a robust barrier to prevent these microorganisms from invading the rest of our bodies.
![](https://scx1.b-cdn.net/csz/news/tmb/2019/spacetravelc.jpg)
Source:
https://phys.org/news/2019-11-space-gut-leaky.html