The simple idea (no memorising)
The name means "yellow body" — that's just how it looks. Think of it as a two‑week caretaker. Its whole job is to make progesterone (plus some estrogen), keeping the womb lining plump and welcoming in case a fertilised egg arrives.
But the caretaker needs to be paid to stay:
- No pregnancy → the LH support fades → the corpus luteum shrivels → progesterone falls → the lining is shed as a period.
- Pregnancy → the tiny embryo makes a hormone called hCG → hCG "pays" the corpus luteum to keep going for about 10–12 weeks, until the placenta takes over.
The clever detail
hCG is the pregnancy‑test hormone. The very same signal that keeps the corpus luteum alive is the one a urine pregnancy test detects. So the biology and the test are the same story.
Why it matters
This explains the rhythm of every cycle: the period comes because progesterone falls when the caretaker leaves. And it explains early pregnancy: hCG is what keeps everything running until the placenta is ready.
Quick check ✅
- What does the corpus luteum make, and for roughly how long if there's no pregnancy?
- Which hormone rescues the corpus luteum in pregnancy — and what everyday test detects it?
Remember this 🌟
Where we're going next → We've followed the ovary. Now let's watch what the womb lining is doing at the very same time. Concept 11.