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Questions and Answers
What is the primary function of the zona pellucida in human fertilization?
What is the primary function of the zona pellucida in human fertilization?
Which of these structures is NOT directly involved in the transport of the ovum from the ovary to the uterus?
Which of these structures is NOT directly involved in the transport of the ovum from the ovary to the uterus?
What is the primary mechanism responsible for the directed movement of the ovum through the fallopian tube?
What is the primary mechanism responsible for the directed movement of the ovum through the fallopian tube?
Which of the following statements is TRUE about the process of ovulation?
Which of the following statements is TRUE about the process of ovulation?
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What prevents polyspermy after fertilization?
What prevents polyspermy after fertilization?
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What is the primary role of the cervical mucus during the menstrual cycle?
What is the primary role of the cervical mucus during the menstrual cycle?
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How does the uterus contribute to sperm transport?
How does the uterus contribute to sperm transport?
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What happens to sperm during the process of capacitation?
What happens to sperm during the process of capacitation?
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What is the primary role of the acrosome reaction in fertilization?
What is the primary role of the acrosome reaction in fertilization?
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What is the primary function of the zona pellucida?
What is the primary function of the zona pellucida?
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Which of the following statements accurately describes the role of the fast block to polyspermy?
Which of the following statements accurately describes the role of the fast block to polyspermy?
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What is the primary role of the cortical reaction in preventing polyspermy?
What is the primary role of the cortical reaction in preventing polyspermy?
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What is the approximate lifespan of sperm once deposited in the female reproductive tract?
What is the approximate lifespan of sperm once deposited in the female reproductive tract?
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How does the cervical mucus help to maintain the viability of sperm?
How does the cervical mucus help to maintain the viability of sperm?
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Which of the following is NOT a barrier that sperm must overcome to reach the egg?
Which of the following is NOT a barrier that sperm must overcome to reach the egg?
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What is the primary mechanism by which the majority of sperm are eliminated from the female reproductive tract?
What is the primary mechanism by which the majority of sperm are eliminated from the female reproductive tract?
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Which part of the oviduct is generally considered the site of fertilization?
Which part of the oviduct is generally considered the site of fertilization?
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What is the primary trigger for the acrosome reaction in many species?
What is the primary trigger for the acrosome reaction in many species?
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What role do prostaglandins play in sperm transport?
What role do prostaglandins play in sperm transport?
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What is the main difference between the fast and slow blocks to polyspermy?
What is the main difference between the fast and slow blocks to polyspermy?
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What substance is primarily responsible for opening the uterotubal junction and allowing the ovum to enter the uterus?
What substance is primarily responsible for opening the uterotubal junction and allowing the ovum to enter the uterus?
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During which phase of sperm transport does the buffering effect of seminal fluid significantly alter the pH of the upper vagina?
During which phase of sperm transport does the buffering effect of seminal fluid significantly alter the pH of the upper vagina?
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Which of these is NOT a factor influencing the rate of sperm transport in the female reproductive tract?
Which of these is NOT a factor influencing the rate of sperm transport in the female reproductive tract?
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Where does fertilization typically occur in humans?
Where does fertilization typically occur in humans?
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What is the primary function of the cervix during sperm transport?
What is the primary function of the cervix during sperm transport?
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Study Notes
Ovulation and Egg Transport
- Ovulation involves the expulsion of antral fluid and the ovum from the ovary into the peritoneal cavity.
- The FSH and LH surge, triggered by estrogen, initiates the process.
- Corona radiata: A layer of granulosa cells surrounding the oocyte.
- Zona pellucida: A glycoprotein layer around the oocyte.
- 13 microns thick in humans.
- Composed of sulfated glycoproteins.
- Mediates sperm binding and the acrosome reaction.
- Prevents polyspermy (multiple sperm entry).
- Acts as a filter during early cleavage divisions.
- Prevents premature implantation.
- The ovary and uterine tube are not directly connected; the ovum is released into the peritoneal cavity.
- Egg transport:
- Follicular rupture near the fimbriae (infundibulum) of the oviduct.
- Fimbriae: Finger-like projections that sweep the egg into the oviduct.
- Ciliated epithelial cells and smooth muscle contractions actively move the ovum to the ampulla.
- Ampulla: The widest part of the fallopian tube where fertilization usually occurs.
- Fertilization occurs at the ampulla or ampulla/isthmus junction.
- The fertilized ovum travels to the isthmus and then the uterus.
- Tubal transport takes 3-4 days.
- Slow transport (72 hours) in ampulla; rapid phase (8 hours) through the isthmus and uterus.
- Progesterone is necessary for egg passage through the uterotubal junction. It opens the uterine lumen.
Sperm Transport
- Sperm is deposited in the upper vagina (pH rapidly elevates to 7.2 from 4.3).
- Sperm transverses the cervix (fast and slow phases).
- Sperm travels through the uterus.
- Sperm enters uterine tubes.
- Sperm travels up the uterine tube via swimming and tube contractions.
- Only a few sperm are near the egg at a time.
- Fertilization occurs in the uterine tube.
- Sperm Transport: Upper Vagina
- Seminal fluid, deposited during copulation, protects sperm from vaginal acidity.
- Buffering effect lasts only minutes.
- Sperm Transport: Cervix
- Cervix is a major barrier and acts as a reservoir.
- Estrogen influences production of copious, transport-regulating mucus.
- Cervical mucus composition varies through the menstrual cycle.
- Function of the Cervix:
- Filters immotile sperm.
- Is receptive to sperm during ovulation.
- Protects sperm from the vagina.
- Rapid Transport in the cervix:
- Rapid penetration of cervical mucus and transport to the uterine tubes (within an hour).
- Muscular movements of the female tract contribute.
- Colonization of Sperm Reservoirs:
- Many sperm are trapped in cervical crypts.
- Facilitated by cervical mucus.
- Slow Release and Transport: Cervix
- Sperm swims through mucus (2-3 mm/hr).
- Storage in crypts, sequential release.
- Prolonged passage is facilitated by mucus and reservoir.
- Sperm Transport in the Uterus:
- Uterine smooth muscle contractions aid transport.
- Sperm motility is not the primary means of uterine entry.
- Sperm enters one oviduct (chance or chemoattractant from the egg).
- Sperm Transport in the Oviduct
- Facilitates simultaneous transport of sperm and eggs.
- Limited sperm presence in oviduct musculature.
- Contraction frequency regulated by hormones, seminal plasma, and prostaglandins.
- Survival of Spermatozoa:
- Sperm has a limited lifespan (80 hrs).
- Cervical mucus helps in metabolic needs.
- Sperm is separated from seminal plasma rapidly.
- Capacitation occurs during passage.
- Loss of Spermatozoa:
- Few reach the site of fertilization.
- Elimination at barriers (cervix, uterotubal junction).
- Damaged/immotile sperm are removed by phagocytosis.
- Capacitation:
- Physiological changes in spermatozoa allowing penetration.
- Glycoprotein surface alteration.
- Fertilization:
- Sperm penetrating the corona radiata to intermingling of chromosomes.
- Usually in the ampullary part of the uterine tube.
Fertilization Processes
- Penetration of corona radiata:
- Around 12 spermatozoa surround the corona.
- Hyaluronidase (from acrosome) may aid in penetration.
- Sperm motility is crucial.
- Binding to Zona and Acrosomal Reaction:
- Triggered in some species by zona pellucida components.
- Acrosomal Reaction:
- Fusion of sperm plasma membrane with outer acrosomal membrane.
- Release of enzymes (hyaluronidase, acrosin) to digest zona pellucida.
- Prevention of Polyspermy:
- Fast block: Rapid depolarization of egg plasma membrane.
- Slow block: Cortical reaction.
- Cortical Reaction:
- Release of cortical granule contents.
- Propagation of calcium wave.
- Hydrolyze sperm receptor molecules in zona pellucida (zona block).
- Summary: Sperm's journey through the female tract is riddled with barriers before the successful fusion with the oocyte occurs.
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Description
This quiz covers the physiological processes of ovulation and the transport of the egg post-ovulation. It delves into the hormonal triggers, the structure of the egg, and the mechanisms that facilitate its journey to the uterus. Test your understanding of the anatomical and biochemical aspects of female reproduction.
