35 Questions
What event initiates Meiosis II in the oocyte?
LH surge
What is the role of collagenase activity in the ovary during ovulation?
Affects collagen fibers surrounding the follicle
What is the function of the avascular spot called the stigma?
Identifying the site of ovulation
Which hormone increases in response to the LH surge during ovulation?
Prostaglandin
What role do local muscular contractions play in the process of ovulation?
Extrude the oocyte
What is the purpose of the zona pellucida during fertilization?
To facilitate and maintain sperm binding
How many spermatozoa reach the site of fertilization out of the 200 to 300 million deposited in the female genital tract?
300 to 500
What does the penetration of the corona radiata by spermatozoa involve?
Passing freely through corona cells
At what phase does the release of lysosomal enzymes from cortical granules occur?
Phase 2: Penetration of the Zona Pellucida
What is the main function of the zona reaction in fertilization?
Prevent sperm penetration and inactivate receptor sites for spermatozoa on the zona surface
What is the function of the yellowish luteal cells in the ovary during the early stages of pregnancy?
Secrete progesterone until the end of the fourth month
What happens if the corpus luteum of pregnancy is removed before the fourth month?
Usually leads to abortion
What is the main role of fimbriae in relation to the ovary and uterine tube?
Collect the oocyte and sweep it into the uterine tube
What is the significance of the zona pellucida during fertilization?
Allows penetration by spermatozoa
What is the purpose of the acrosome in sperm during fertilization?
Aid in penetration through barriers like corona radiata
What is the term used for one of the daughter cells that receives hardly any cytoplasm?
Second polar body
Which cellular component carries the activating factor in the egg during fertilization?
Spermatozoon
What event marks the initial cellular and molecular events associated with early embryogenesis?
Activation
What is the term used for the vesicular nucleus where the chromosomes of the definitive oocyte arrange themselves?
Female pronucleus
What is the consequence if each pronucleus in the two-cell zygote does not replicate its DNA?
Each cell has half the normal amount of DNA
Where does fertilization typically occur in the female reproductive system?
Ampullary region of the uterine tube
What is the process by which male and female gametes fuse known as?
Fertilization
How long can sperm remain viable in the female reproductive tract?
Days
What is the widest part of the uterine tube where fertilization usually occurs?
Ampulla
What can happen to sperm after reaching the isthmus?
They cease their migration
What stimulates sperm to become motile again at ovulation?
Chemoattractants produced by cumulus cells
What part of the female reproductive system do only 1% of sperm deposited in the vagina enter?
Cervix
What is the phase where chromosomes become arranged on the spindle, split longitudinally, and move to opposite poles called?
Anaphase
What is the final result of fertilization?
Blastocyst
What is the term for the process by which male and female pronuclei fuse?
Fertilization
What is the phase in which the plasma membrane of the sperm and egg fuse?
Phase 3: Fusion of the oocyte and sperm cell membranes
What happens to the zona pellucida after the oocyte releases cortical granules?
Its structure and composition are altered to prevent sperm binding and penetration
What is the fate of the plasma membrane covering the acrosomal head cap after the acrosome reaction?
It fuses with the oocyte membrane
What is the role of integrins on the oocyte during fertilization?
Mediate initial adhesion of sperm to the oocyte
Which enzyme-containing granules contribute to making the oocyte membrane impenetrable to other spermatozoa?
Lysosomal enzymes in cortical oocyte granules
Study Notes
Oocyte Maturation and Fertilization
- After ovulation, the oocyte is released from the ovary and travels through the oviduct, guided by fimbriae.
- The oocyte is surrounded by corona radiata cells and zona pellucida, which facilitate and maintain sperm binding and induce the acrosome reaction.
- Capacitated sperm penetrate the corona radiata, and one sperm fertilizes the egg.
Pronuclei Formation and Fusion
- The fertilized oocyte receives hardly any cytoplasm, and one daughter cell becomes the second polar body; the other daughter cell is the definitive oocyte.
- Chromosomes of the oocyte (22 + X) arrange themselves in a vesicular nucleus, the female pronucleus.
- The spermatozoon moves forward and its nucleus swells to form the male pronucleus.
- The male and female pronuclei come into close contact, lose their nuclear envelopes, and replicate their DNA in preparation for mitotic division.
Phases of Fertilization
- Phase 1: Penetration of the corona radiata by the spermatozoon.
- Phase 2: Penetration of the zona pellucida by the spermatozoon, facilitated by the acrosome reaction.
- Phase 3: Fusion of the sperm and oocyte cell membranes, allowing the sperm nucleus to enter the oocyte cytoplasm.
Corpus Luteum and Hormone Regulation
- If fertilization does not occur, the corpus luteum shrinks, and progesterone production decreases, leading to menstrual bleeding.
- If the oocyte is fertilized, human chorionic gonadotropin prevents corpus luteum degeneration, and progesterone production continues, maintaining pregnancy.
Early Embryonic Development
- The fertilized oocyte begins dividing, and the zygote forms a two-cell stage.
- The developing embryo travels through the oviduct and reaches the uterine lumen in approximately 3-4 days.
Corpus Albicans and Luteolysis
- After ovulation, the corpus luteum develops from the ruptured follicle.
- If the oocyte is not fertilized, the corpus luteum degenerates (luteolysis), and progesterone production decreases.
- Luteolysis leads to the formation of the corpus albicans, a mass of fibrotic scar tissue.
Test your knowledge on the ovarian structure and the role of luteal cells in secreting progesterone during pregnancy. Questions may include the relation between fim briae and ovary, corpus luteum removal, and pregnancy maintenance.
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