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Questions and Answers
What is the primary role of fertilization cleavage in early development?
What is the primary role of fertilization cleavage in early development?
- Establish multicellularity without increasing cytoplasm volume (correct)
- Prepare the zygote for implantation in the uterus
- Increase cytoplasm volume for cellular processes
- Facilitate nutrient absorption from the maternal blood
Which layer of the blastocyst is responsible for forming the placenta?
Which layer of the blastocyst is responsible for forming the placenta?
- Trophoblast (correct)
- Cytotrophoblast
- Embryoblast
- Syncytiotrophoblast
What occurs during the apposition phase of implantation?
What occurs during the apposition phase of implantation?
- The syncytiotrophoblast secretes progesterone
- The embryoblast develops into the fetus
- The zona pellucida envelops the blastocyst for protection
- The blastocyst approaches and attaches to the endometrium (correct)
Which hormone is secreted by the syncytiotrophoblast during implantation?
Which hormone is secreted by the syncytiotrophoblast during implantation?
What characterizes the structure of the blastocyst at 4-5 days post-fertilization?
What characterizes the structure of the blastocyst at 4-5 days post-fertilization?
What is the primary outcome of fertilisation?
What is the primary outcome of fertilisation?
During which stage is the primary oocyte arrested in oogenesis?
During which stage is the primary oocyte arrested in oogenesis?
What is the term for the division of the prenatal period into 3 segments?
What is the term for the division of the prenatal period into 3 segments?
What type of cell results from the transformation of spermatids during spermiogenesis?
What type of cell results from the transformation of spermatids during spermiogenesis?
Which of the following describes the acrosomal reaction?
Which of the following describes the acrosomal reaction?
What is a teratogen?
What is a teratogen?
At what stage does cleavage begin after fertilisation?
At what stage does cleavage begin after fertilisation?
What happens to the secondary oocyte if fertilisation does not occur?
What happens to the secondary oocyte if fertilisation does not occur?
Flashcards
Gamete
Gamete
A specialized haploid (n) reproductive cell, like a sperm or egg cell.
Spermatogenesis
Spermatogenesis
The formation of sperm cells in the testes. It involves two rounds of cell division (meiosis) and a final maturation process.
Oogenesis
Oogenesis
The formation of the ovum (egg cell) in the ovary. It begins in the fetal period and is completed after fertilization.
Fertilization
Fertilization
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Teratogen
Teratogen
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Mutagen
Mutagen
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Cleavage
Cleavage
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Blastocyst
Blastocyst
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Cleavage (in embryonic development)
Cleavage (in embryonic development)
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Trophoblast
Trophoblast
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Embryoblast
Embryoblast
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Implantation
Implantation
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Human Chorionic Gonadotropin (hCG)
Human Chorionic Gonadotropin (hCG)
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Study Notes
Gametes and Fertilization
- Gamete: Specialized haploid (n) reproductive cell
- Sperm cells: Male gamete
- Egg cell/ovum: Female gamete
- Embryo: Developing human being (weeks 1-8)
- Fetus: Developing human being (weeks 9-36)
- Trimester: 3-month division of the 9-month prenatal period
- Teratogen: Substance causing developmental anomaly (e.g., alcohol, thalidomide, virus, lead, radiation)
- Mutagen: Agent causing genetic mutations (e.g., aflatoxins, HPV)
Gametogenesis
- Spermatogenesis: Sperm formation in testes
- Meiosis I: Primary spermatocyte (2n) → 2 haploid cells
- Meiosis II: Secondary spermatocytes → 4 haploid cells
- Spermiogenesis: Spermatids mature into spermatozoa
- Oogenesis: Ovum/egg formation in ovary
- Begins in fetal period
- Oogonium → primary oocyte
- Primary oocyte arrests in prophase I (meiosis I).
- Primary oocyte matures into secondary oocyte at puberty but arrests at metaphase II.
- Secondary oocyte matures into ovum only with fertilization.
Fertilization
- Fertilization: Sperm and ovum unite to form a zygote (in fallopian tube's ampulla)
- Stages of Fertilization:
- Gamete transport to uterine ampulla
- Sperm capacitation: Final sperm preparation for ovum penetration
- Acrosomal reaction (sperm release hyaluronidase to penetrate ovum)
- Cortical/zona pellucida reaction (ovum prevents polyspermy)
- Syngamy (fusion of pronuclei)
Outcomes of Fertilization
- Diploid number restored (2n): in zygote
- Sex determination: Sperm (X or Y chromosome)
- Cleavage initiation: Rapid cell division of zygote
- Genetic diversity: Combination of parental genetic material
Cleavage
- Zygote: Single-celled stage
- Blastomere formation: 2-8 blastomeres
- Morula: 16-23 blastomeres
- Blastula: Hollow ball of cells
- Blastocyst: Blastula with cavity
- Importance of Cleavage: Establishes multicellularity, decreases cell size, and prepares for implantation/gastrulation
Blastocyst Structure
- Formation: 4-5 days post-fertilization
- Layers: Trophoblast (outer) and embryoblast (inner)
- Zona pellucida: Surrounds both layers
- Implantation: Trophoblast at embryonic pole
- Embryo development: Embryoblast → embryo
- Placenta formation: Trophoblast → placenta
Implantation
- Apposition: Blastocyst approaches uterine wall (posterior/anterior)
- Trophoblast differentiation: Cytotrophoblast and syncytiotrophoblast
- Endometrial penetration: Syncytiotrophoblast penetrates endometrium
- HCG secretion: Syncytiotrophoblast secrets human chorionic gonadotropin
- Corpus luteum: Maintains pregnancy (secretes progesterone)
- Layers of trophoblast: Cytotrophoblast faces embryoblast; syncytiotrophoblast faces away from embryoblast
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