Upon ejaculation, about 200 – 600 million sperm are deposited near the cervical os of the uterus and posterior fornix of the vagina.
They must endure a period of capacitation before they are capable of fertilization.
- Only capacitated sperm can go through the corona radiata to contact the zona pellucida and initiate the acrosome reaction.
- Upon contact with the plasmalemma of the secondary oocyte, the sperm cell initiates cortical reaction, which causes the secondary oocyte membrane to become impermeable to any other spermatozoa.
- After the sperm cell nucleus enters the secondary oocyte, the secondary oocyte completes meiosis II to become an ovum and second play body.
- Fertilization generally occurs in the distal 1/3 of the uterine tube (oviduct), the portion called the ampulla.