Fertilization and Gamete Transfer Quiz

Human Reproductive Biology: Fertilization and Sperm Transport

• Semen thickens upon entry into the vaginal canal, but liquefies again after 20 minutes, increasing vaginal pH to 7.2.
• Orgasm induces rhythmic contractions in the vagina which move sperm towards the cervix and uterus.
• Cervical mucus liquefies around ovulation allowing sperm to pass into the uterus, but only about 1 million sperm make it through the cervix.
• Sperm "climb" up the uterus aided by uterine contractions and cilia action, but many are targeted by macrophages.
• The oviduct acts as a temporary storage area for sperm, with many swimming past the ovulated egg.
• Capacitation and hyperactivation of sperm are necessary for fertilization, enabling them to survive in the reproductive tract for up to 6 days.
• Fertilization is most likely to occur in the 5 days before ovulation and the day of ovulation.
• Steps of fertilization involve penetration of the cumulus oophorus, zona pellucida, attachment to the egg plasma membrane, cortical reaction, completion of meiosis II, and pronuclei generation.
• Hyaluronidase in sperm breaks down hyaluronic acid in the cumulus oophorus, allowing sperm to reach the zona pellucida.
• Sperm recognition of a glycoprotein in the zona pellucida triggers the acrosome reaction, leading to the degradation of the zona pellucida.
• Completion of meiosis II in the egg after fertilization removes extra DNA copies and creates the second polar body.
• The egg and sperm pronuclei migrate towards each other, replicate their DNA, and fuse to create the zygote. The primary sex ratio is 120:100 for early aborted embryos and 105:100 for births.

Test your knowledge about fertilization, gamete transfer, and the process of conception in human reproduction.