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Questions and Answers
What is the primary role of mitochondria in spermatozoa?
What is the primary role of mitochondria in spermatozoa?
Which part of the spermatozoon is responsible for motility?
Which part of the spermatozoon is responsible for motility?
What occurs during the process of capacitation?
What occurs during the process of capacitation?
In terms of chromosome composition, a mature spermatozoon contains how many chromosomes?
In terms of chromosome composition, a mature spermatozoon contains how many chromosomes?
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At which location does fertilization typically occur within the female reproductive system?
At which location does fertilization typically occur within the female reproductive system?
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What triggers the acrosome reaction during fertilization?
What triggers the acrosome reaction during fertilization?
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What is the result of the cleavage process after fertilization?
What is the result of the cleavage process after fertilization?
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During which stage is the morula formed, and what is its nutritional source?
During which stage is the morula formed, and what is its nutritional source?
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What is the fate of the zona pellucida just before implantation of the blastocyst?
What is the fate of the zona pellucida just before implantation of the blastocyst?
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Which phase of fertilization involves the fusion of the sperm head and oocyte cell membranes?
Which phase of fertilization involves the fusion of the sperm head and oocyte cell membranes?
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Study Notes
Fertilization, Cleavage & Implantation
- Fertilization: The process of mature sperm and ovum meeting and fusing to form a zygote.
- Site of fertilization: Ampullary part (lateral third) of the uterine tube.
- Spermatozoa stages: Must undergo capacitation and acrosome reaction to be capable of fertilization.
Spermatozoa Structure
- Head: Contains the nucleus and the acrosome (enzymes for penetrating the ovum).
- Middle piece: Contains mitochondria for motility.
- Tail (flagellum): Responsible for motility, similar structure to cilia.
Fertilization Steps
- Phase 1: Penetration of the corona radiate.
- Phase 2: Penetration of the zona pellucida.
- Phase 3: Fusion of the oocyte and sperm head cell membranes.
Results of Fertilization
- Restoration of the diploid number of chromosomes.
- Determination of the sex of the new individual.
- Initiation of cleavage. (Without fertilization, the ovum degenerates 24 hours after ovulation).
Cleavage
- Definition: A series of mitotic divisions increasing the number of cells.
- Site: Uterine tubes (medial to the ampulla).
- Morula stage: Early stage of embryo development (12-16 blastomeres).
Blastocyst Formation
- Formation: Fluid from uterine cavity enters the morula, forming a blastocoele (cavity) and blastomeres are divided into inner cell mass (embryoblast) and outer cell mass (trophoblast).
- Zona Pellucida: Disappears before implantation.
Implantation
- Definition: Blastocyst penetrates the uterine endometrium.
- Time: Begins at the end of the first week (6th day). Complete by the 11th day.
- Normal site: Anterior or posterior wall of the uterus.
- Mechanism: Trophoblast proliferates (inner cellular layer—cytotrophoblast, outer multinucleated layer—syncytiotrophoblast). Syncytiotrophoblast erodes uterine tissues, enabling blastocyst to embed.
- Decidua: Endometrium after implantation.
Types of Decidua
- Decidua basalis: Part of endometrium at the base of the implanted blastocyst, forming the maternal part of the placenta.
- Decidua capsularis: Part of endometrium covering the implanted blastocyst.
- Decidua parietalis: Part of endometrium lining the rest of the uterine cavity.
- Decidua marginalis: Part where decidua capsularis and parietalis meet.
Abnormal Implantation (Ectopic Pregnancy)
- Definition: Implantation outside the uterine cavity.
- Common Sites: Fallopian tubes.
- Placenta Previa: Implantation of blastocyst in the lower uterine segment (lower than normal).
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Description
This quiz covers the intricate processes of fertilization, cleavage, and implantation. It explores the phases of fertilization, the structure of spermatozoa, and key results of the fertilization process. Test your knowledge on these essential concepts in reproductive biology.
