Retrograde menstruation.

Because the feliciano tubes aren’t closed on the ends, where they interact with the ovaries, blood from a period can flow backwards into your abdominal cavity.

Additionally, a small amount of sperm (if a woman is sexually active and say trying for a baby) can also go the full way and leak into the abdominal cavity.

So some women can have blood and semen free floating in their abdominal cavity. Between organs

Got any DOIs to share? I’d like to read about some bioreactors and polymer physics.

I’ve worked for about a year as a waiter when I was younger. Compared to what I do now, there was virtually no skill involved.