The simple idea (no memorising)
The lining (the endometrium) has two phases that mirror the ovary's two halves:
- Proliferative phase — driven by estrogen. The lining grows thicker; its glands are short and straight, like new grass.
- Secretory phase — driven by progesterone after ovulation. The glands become coiled and juicy, filling with nourishing secretions — a soft bed ready for an embryo.
The tell‑tale sign of ovulation
Just after ovulation, tiny gaps called subnuclear vacuoles appear under the microscope in the lining's cells. They are the earliest proof that ovulation has happened — the lining's own way of announcing "the egg has been released." You don't need the detail; just enjoy that the lining keeps a receipt.
A picture for your mind
First estrogen lays the turf (proliferative). Then progesterone waters and softens it into a lawn (secretory). If no one comes to use the lawn, it's rolled up and removed — the period.
Why it matters
Reading the lining tells you the hormone story. A thick, secretory lining means progesterone was here, so ovulation happened. A lining that's only ever proliferative hints that ovulation is not happening — the key clue in the next concept and in PCOS.
Quick check ✅
- Which hormone drives the proliferative phase, and which the secretory phase?
- What early microscopic sign shows that ovulation has occurred?
Remember this 🌟
Where we're going next → If no embryo arrives, that carefully prepared lining is shed. Why, exactly? Concept 12.