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Topic 11 Continuity, Hormonal Regulation during Gestation, Determination…
Topic 11 Continuity
Development Process
Prenatal development
- Fertilization, or conception
- Fusion of two haploid (n) gametes, each 23 chromosomes.
- Produces a zygote (46 chromosomes), the normal diploid (2n).
- Occur within a day after ovulation.
Fertilization process
- Oocyte at ovulation
- Fertilization and oocyte activation
- Pronuclei develop, and DNA synthesis occurs
- Spindle formation begins
- Amphimixis occurs, and cleavage begins
- 1st cleavage forms two blastomeres
- Pre embryonic development
Pre embryonic period
- Cleavage
- Implantation
The Embryonic Period
- Placentation
- Embryogenesis
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Trimester
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Second trimester
Week 13 to 26, the fetus grows about 0.6 kg
Third trimester
Week 27 until 40, most organ systems become ready for normal functioning
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Sexual differentiation
Male gonads begin their testes development during week 7 of gestation. Female gonad, ovaries is developed in week 8. The structure arise from the gonadal ridge.
In male, genital tubercles enlarge forming the penis and labioscrotal swelling becoming scrotum.
Failure of the testes to make their normal descent result in cryptorchidism.
Causes sterility and increased risk of testicular cancer.
In F, genital tubercles give rise to the clitoris and labioscrotal swelling becoming labia majora and minora.
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Function of Placenta
Supply oxygen and nutrients, carbon dioxide and other wastes removed
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