19 Questions
What is the average number of sperm in a single ejaculation?
182 million
Which part of the sperm contains many enzymes vital for fertilization?
Acrosome
What is continually being replenished to create semen?
Seminal fluid
What are the components of seminal plasma?
Solvents, mucus, enzymes, energy sources, zinc, prostaglandins, and ATP
What is the most common type of twins?
Fraternal twins (dizygotic)
Which type of twins results from one ova and one sperm spontaneously splitting?
Identical twins (monozygotic)
What is the term for the development of a new zygote without a fertilization event?
Parthenogenesis
Which chromosomal aberration represents less than 1% of human embryos?
Triploidy – 3 copies of each chromosome
What is the pH of the vaginal canal after semen liquefies?
7.2
What is the approximate number of sperm that make it through the cervix?
1 million
What enables sperm to survive in the reproductive tract for up to 6 days?
Capacitation and hyperactivation
When is fertilization most likely to occur?
5 days before ovulation and the day of ovulation
What does hyaluronidase in sperm break down?
"Hyaluronic acid" in the cumulus oophorus
What triggers the acrosome reaction in sperm?
"Glycoprotein" in the zona pellucida
What happens after fertilization with regards to meiosis II?
Completion of meiosis II removes extra DNA copies and creates the second polar body.
What does the primary sex ratio refer to?
The ratio of male to female embryos early aborted.
What enables sperm to pass through cervical mucus around ovulation?
Liquefaction of cervical mucus around ovulation.
What aids sperm 'climbing' up the uterus?
Uterine contractions and cilia action.
Where do many sperm swim past without fertilizing an egg?
Oviduct.
Study Notes
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.
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