Timeline from Ovulation to Implantation
| Time Post-Fertilization | Event |
|---|---|
| Day 0 | Ovulation; secondary oocyte in ampulla |
| Day 0–1 | Fertilization (ampulla): acrosomal reaction → sperm entry → cortical reaction → meiosis II completion → zygote |
| Day 1–2 | Cleavage: 2-cell → 4-cell (fallopian tube, moving toward uterus) |
| Day 4 | Morula (16-cell solid ball) |
| Day 5 | Blastocyst (trophoblast + ICM + blastocoel) |
| Day 5–6 | Zona pellucida hatching |
| Day 6–7 | Implantation in endometrium |
| Day 7–8 | Trophoblast secretes hCG (detectable ~10 days post-implantation) |
Blastocyst Structure
- Trophoblast (outer) → placenta + hCG secretion
- Inner cell mass (ICM) → embryo
- Blastocoel → fluid-filled internal cavity