Phase 1 · Understand the Body — Why the disease behaves the way it does.
The One-Line Truth
The whole disease in one chain
Everything on this page exists to explain this line.
Tissue that looks and acts like the lining of the uterus grows outside the uterus, bleeds every month with your period, and causes pain, scarring, and trouble getting pregnant.
A Pipe System with Backflow and Rusted Joints
Imagine your uterus is a pipe that drains water (menstrual blood) downward through a single outlet (the cervix and vagina) every month. Normally, water flows one way and exits cleanly. But in endometriosis, some water backs up into side pipes (the fallopian tubes) and leaks into the walls and surrounding pipes (the pelvis, ovaries, and bowel), where it does not belong. Because the water contains living cells from the main pipe's lining, those cells stick to the walls of the side pipes and surrounding plumbing, survive, and keep growing there, responding to the same monthly signals that make the main pipe swell. Each month, these rogue colonies swell and leak again, irritating the surrounding pipes. The body tries to patch the leaks with scar tissue (rust and corrosion), but instead of fixing the problem, the patches glue pipes together, kink them, and trap organs in fixed, painful positions. Over time, the entire plumbing system becomes distorted, blocked, and painful.
ACOG Practice Bulletin No. 114, 2010 (reaffirmed 2022): Management of Endometriosis · ESHRE (European Society of Human Reproduction and Embryology) Guideline on Endometriosis, 2022 · American Society for Reproductive Medicine (ASRM) Endometriosis Guidelines, 2021 · reviewed 2026-07-07