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So, our entire digestive system is technically the "outside" of out bodies. Our immune system keeps most little breaches that might happen under control. There also a healthy supply of "good" bacteria inside of us, that usually helps keep "bad" bacteria from taking hold.

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They're being exposed to bacteria that are already present in your lower digestive tract. Those bacteria can be harmful if you eat them (fecal-oral is a very common way that food poisoning bacteria spread), but they're not dangerous in your intestines or (directly) dangerous on your skin (except that having them on the skin of, say, your hands can be a good way to end up with them in your mouth).

First reason is that mucosal tissue creates a physical barrier that is very hard for microbes to get through. Additionally, the vast majority of lymphocytes in your body are found in those tissues. And your immune system is just in general much more active there too. When cells detect an invading organism they don't call for help, they just initiate the immune response themselves.

Of course, it would be horrible for our entire bodies to be composed of this sort of tissue. its great against microbes, but not so great about mechanical damage. So you only find it where its most important.

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also your tongue, if it gets a cut it rarely gets infected, it makes its own antibacterial proteins

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Your submission has been removed for the following reason(s):

Top level comments (i.e. comments that are direct replies to the main thread) are reserved for explanations to the OP or follow up on topic questions.

Joke only comments, while allowed elsewhere in the thread, may not exist at the top level.

If you would like this removal reviewed, please read the detailed rules first. **If you believe it was removed erroneously, explain why using this form and we will review your submission.

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You mean they aren't meant to?

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Like a Klein bottle!

I don't know if your intestines require the 4th dimension, but mine are rather like a donut.

More like a doughnut (or a mug)

Additionally, all bacteria and microbes, that come out of your butt have already been inside your body, so you cannot get any "new" infections this way. Nevertheless, getting as many of them out without re-entering helps a lot

Depending on what I eat....sometimes it seems like my system folds space and time and just shoots that shit out of me almost immediately.

Saliva right ? It’s a natural painkiller

I dont know about that, we have our flora in the mouth, might not be good if we eat a lot of sugar, they fight other nasty bacteria that is much worse for us

Seems like a perfect ELI5 answer! Well done

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