Podcast
Questions and Answers
Where does fertilization typically occur?
Where does fertilization typically occur?
- In the ampullary region of the uterine tube (correct)
- In the vagina
- In the cervix
- In the ovary
What percentage of sperm deposited in the vagina enter the cervix?
What percentage of sperm deposited in the vagina enter the cervix?
- 10%
- 5%
- 20%
- 1% (correct)
How do sperm primarily move from the cervix to the oviduct?
How do sperm primarily move from the cervix to the oviduct?
- By uterine contractions
- By movements of fluids created by uterine cilia
- By the movement of the oviduct
- By their own propulsion (correct)
What is the minimum time required for sperm to travel from the cervix to the oviduct?
What is the minimum time required for sperm to travel from the cervix to the oviduct?
What occurs in the isthmus that affects sperm motility?
What occurs in the isthmus that affects sperm motility?
What is the duration of capacitation in the human reproductive tract?
What is the duration of capacitation in the human reproductive tract?
What is the last phase of fertilization?
What is the last phase of fertilization?
Approximately how many sperm reach the site of fertilization?
Approximately how many sperm reach the site of fertilization?
What is the main mechanism of action of the combination contraceptive pill?
What is the main mechanism of action of the combination contraceptive pill?
What is a disadvantage of In Vitro Fertilization (IVF)?
What is a disadvantage of In Vitro Fertilization (IVF)?
What is the role of the drug RU-486 in contraception?
What is the role of the drug RU-486 in contraception?
Why are multiple ova collected and fertilized in IVF?
Why are multiple ova collected and fertilized in IVF?
What is the primary mechanism of action of the intrauterine device (IUD)?
What is the primary mechanism of action of the intrauterine device (IUD)?
What is the purpose of intracytoplasmic sperm injection (ICSI)?
What is the purpose of intracytoplasmic sperm injection (ICSI)?
What is the approximate number of sperm per ml in a normal ejaculate?
What is the approximate number of sperm per ml in a normal ejaculate?
What is the percentage of couples who experience infertility?
What is the percentage of couples who experience infertility?
In Zygote Intrafallopian Transfer (ZIFT), where are the fertilized oocytes placed?
In Zygote Intrafallopian Transfer (ZIFT), where are the fertilized oocytes placed?
What is the main mechanism of action of the male 'pill'?
What is the main mechanism of action of the male 'pill'?
What is a benefit of fertilization using IVF?
What is a benefit of fertilization using IVF?
Why is it necessary for the uterine tubes to be patent in IVF and ZIFT?
Why is it necessary for the uterine tubes to be patent in IVF and ZIFT?
What is the primary cause of occluded oviducts in women?
What is the primary cause of occluded oviducts in women?
What is the definition of fertility in terms of sperm count in males?
What is the definition of fertility in terms of sperm count in males?
What is the function of the zona pellucida?
What is the function of the zona pellucida?
What is released from cortical granules lining the plasma membrane of the oocyte?
What is released from cortical granules lining the plasma membrane of the oocyte?
What is the role of ZP3 protein in the fertilization process?
What is the role of ZP3 protein in the fertilization process?
What happens to the plasma membrane covering the acrosomal head cap during the acrosome reaction?
What happens to the plasma membrane covering the acrosomal head cap during the acrosome reaction?
What is the result of the cortical and zona reactions?
What is the result of the cortical and zona reactions?
What is the main consequence of the second meiotic division?
What is the main consequence of the second meiotic division?
What is the function of integrins in the fertilization process?
What is the function of integrins in the fertilization process?
What is the role of the spermatozoon in metabolic activation of the egg?
What is the role of the spermatozoon in metabolic activation of the egg?
What happens to the spermatozoon after it enters the oocyte?
What happens to the spermatozoon after it enters the oocyte?
What happens to the chromosomes in the male pronucleus during growth?
What happens to the chromosomes in the male pronucleus during growth?
What is the result of the release of acrosomal enzymes?
What is the result of the release of acrosomal enzymes?
What is the result of the failure of DNA replication in the pronuclei?
What is the result of the failure of DNA replication in the pronuclei?
What is the significance of the diploid number of chromosomes in the zygote?
What is the significance of the diploid number of chromosomes in the zygote?
What determines the sex of the new individual?
What determines the sex of the new individual?
What is the consequence of fertilization failure?
What is the consequence of fertilization failure?
What is the result of the movement of sister chromatids to opposite poles?
What is the result of the movement of sister chromatids to opposite poles?
Study Notes
Fertilization
- Fertilization occurs in the ampullary region of the uterine tube, which is the widest part of the tube and is close to the ovary.
- Spermatozoa can remain viable in the female reproductive tract for several days, but only 1% of sperm deposited in the vagina enter the cervix, where they may survive for many hours.
- Sperm movement from the cervix to the oviduct is primarily accomplished by their own propulsion, although they may be assisted by movements of fluids created by uterine cilia.
Capacitation and Acrosome Reaction
- Capacitation is a period of conditioning in the female reproductive tract that lasts approximately 7 hours in humans, during which sperm undergo epithelial interactions with the mucosal surface of the tube.
- The acrosome reaction is induced by zona proteins and culminates in the release of enzymes needed to penetrate the zona pellucida.
Phases of Fertilization
- Phase 1: Penetration of the corona radiata, during which capacitated sperm pass freely through corona cells.
- Phase 2: Penetration of the zona pellucida, which facilitates and maintains sperm binding and induces the acrosome reaction.
- Phase 3: Fusion of the oocyte and sperm cell membranes, which is mediated in part by the interaction of integrins on the oocyte and sperm.
Post-Fertilization Events
- The fertilizing spermatozoon moves forward until it lies close to the female pronucleus, and its nucleus becomes swollen and forms the male pronucleus.
- The oocyte responds to fertilization in three ways: cortical and zona reactions, resumption of the second meiotic division, and metabolic activation of the egg.
Clinical Correlates
- Contraceptive methods include barrier techniques (male and female condoms, diaphragm, cervical cap, and contraceptive sponge), hormonal methods (the pill), and intrauterine devices.
- Infertility affects 15% to 30% of couples, and may be due to male or female factors, such as insufficient numbers of sperm, poor motility, occluded oviducts, hostile cervical mucus, immunity to spermatozoa, and absence of ovulation.
- Assisted reproductive technologies, such as in vitro fertilization (IVF) and zygote intrafallopian transfer (ZIFT), can overcome infertility.
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Description
Fertilization occurs in the ampullary region of the uterine tube, where male and female gametes fuse. Learn about the journey of sperm from the vagina to the oviduct.
