Fertilization is where life, in all its glory and beauty, begins. While passing through reproductive tract, spermatozoa acrosome begins releasing enzymes that enable a sperm to penetrate the zona pellucida. When a spermatozoa enters the oocyte, a zona reaction occurs, which makes the zona pellucida impenetrable to other spermatozoa. The oocyte divides into mature ovum (kept) and polar body (discarded).
- Also see Early embryology