Hemmies and fissures bleed - this means there is an opening. They bleed primarily during bowel movements…therefore there are unnatural pathways into the body being opened at exactly the moment that bacteria-laden waste is passing over the location.
Yet there is never any concern about infections.
If I had a cut finger and plunged it into a pile of poo, even my own poo, it seems to me it would very likely become infected. Perhaps I am mistaken, and I welcome enlightenment. But I’d find that very surprising news.
So…do we know why this doesn’t (usually, anyway) happen with hemmies and fissures?
In fact, there often is entry of bacteria into the bloodstream in the presence of things like bleeding hemorrhoids. But, there is also entry during a normal bowel movement in normal individuals (just as there is with brushing your teeth!). In other words, bacteria entering the bloodstream are a fact of life for all of us virtually every day.
The reason nothing untoward usually happens is at least four-fold: i) if white blood cell defenses are functioning normally (especially the neutrophils), they eliminate any bacteria that have found their way into the blood ii) the amount of bacteria entering the bloodstream during things like bowel movements is relatively small and easily handled by a healthy individual’s white cells iii) most bacteria entering the bloodstream that way are not terribly virulent, i.e. they tend not to cause disease in the first place (OTOH, bugs like Staphylcoccus Aureus and Enterococcus are) iv) in normal people, the lining of the heart valves and blood vessels is not so damaged as to provide a place for bacteria to take up residence there (i.e. after entering the bloodstream, bacteria can lodge and proliferate on the heart valves if that lining is ratty, leading to what’s called endocarditis. There may also be a fifth reason insofar as some types of antibodies (i.e. IGA) specifically protect against infection via breaks in the surface of things like the GI tract)
ETA: On re-reading, I realize I answered a different question! Still, some of what I said is relevant to your question as to ‘why hemorrhoids don’t get infected’, i.e. normally functioning neutrophils
There are plenty of gut bacteria that will happily colonize anywhere in your body, killing you in the process, if given the chance. They’re normally harmless but they are opportunistic motherfuckers. Luckily for us, our immune system keeps them under control.