The simple idea (no memorising)
Recall Concept 3: two Müllerian ducts must (1) form, then (2) fuse their lower halves in the middle, then (3) resorb the wall left between them, leaving one clean cavity. Match the failure to the result:
| Step that fails | What you get |
|---|---|
| Formation fails (one side) | unicornuate (a small, one‑sided womb) |
| Fusion fails completely | didelphys (a double womb, often two cervices) |
| Fusion fails partly | bicornuate (two horns; the outside top is dented) |
| Resorption fails | septate (a wall divides the cavity; the outside looks normal) |
The one distinction to nail
Septate vs bicornuate look similar inside (both have a divided cavity) but differ outside:
- Septate — outside top is smooth/normal; the problem is a leftover wall. (Often fixable through a keyhole procedure.)
- Bicornuate — outside top is dented into two horns.
So imaging must always check both the inside cavity AND the outside contour.
The special case: no womb at all (MRKH)
If the ducts barely form, a woman can have working ovaries but a missing/underdeveloped womb and upper vagina — MRKH syndrome. Because the ovaries are separate (Concept 3), she develops normal breasts and body, but her periods never start. Finding a Müllerian anomaly should also prompt a look at the kidneys, which develop nearby and can be affected too.
Why it matters
These anomalies can cause period problems, pain, infertility or pregnancy loss. Understanding form → fuse → resorb means you can predict the whole family instead of memorising it.
Quick check ✅
- A womb that's normal on the outside but divided inside — which anomaly, and which failed step?
- In MRKH, why are the breasts normal even though there's no womb?
Remember this 🌟
Where we're going next → Structures built in youth can lose their support with age. Concept 25.