eli5 why you don’t get infections from your mouth, nose, or ears often? What’s the difference between those openings and if you had an open wound which could easily get infected
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These openings are covered on the inside by what is known as “mucous membrane”. It’s essentially a different kind of skin that doesn’t grow hair and is usually moist. It’s definitely not an open wound.
TL;DR: saliva, mucus, earwax
Hopefully this doesn’t get deleted for being too short, but each of those three orifices have fluids/solids that explicitly protect against infection.
The mouth has saliva, which indirectly kills bad bacteria by “communicating with” the good bacteria in your mouth: https://malloydevinedental.com/saliva-keeps-bad-bacteria-in-check/
The nose has mucus, which helps prevent bacterial growth, though also indirectly: https://www.nibib.nih.gov/news-events/newsroom/disarming-bacteria-mucus-and-phages
Finally, the ears have ear wax, which also kills bacteria as well as preventing bacteria from entering the inner ear: https://owlcation.com/stem/Ear-Wax-Facts-Functions-and-Health-Problems
These orifices are normally open to the world, so it makes sense for them to be protected.
Conversely, wounds open up parts of our body that aren’t normally exposed to the world and therefore normally don’t have strong protection against bacteria
On the other side, cold viruses and COVID and such enter through the mouth, nose and eyes since they have evolved to attach to molecular receptors present in those orifices
The reality simple answer is bloodstream.
Infections are a threat because they can access the cells and as we all know we are a big complicated donut and our intestine on the outside of our body.
You do get infections from those orifices all the time… Faringitis, gastroenteritis and otitis are an example
There’s “skin*” on the inside of your mouth, nose, and ears.
*Epithelium, which is a more general category than skin. But for ELI5 it’s pretty much skin.
These openings have defense mechanisms in the form of mucous membranes, waxes, acids, enzymes, and/or hairs.
Also, it’s important to note that they are *not* direct openings to the “inside” of your body. The inside of your mouth, nose, ears, etc. are all covered with the same class of tissue that covers the outside of your body (epithelium). Biologically speaking, nothing is actually *inside* your body until it crosses a membrane, so something that is in your mouth, for instance, is not inside of your body. You could swallow a penny and have it travel all the way through and out the other end, and it will never have actually entered your body from a biological standpoint.
lol I do, one drop of water in my ear there’s a solid 50% chance I’ll get ill. Didn’t know for years thought I had a poor constitution. Got older gained weight didn’t do flips in my bath anymore and suddenly I stopped getting sick lol
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