Questions and Answers
What are the three stages of prenatal development?
The germinal stage lasts from fertilization to about 4 weeks of gestational age.
False
What structure forms from the cluster of cells around the edge of the blastocyst before implantation?
embryonic disk
During the germinal stage, the zygote undergoes rapid cell division known as ______.
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Match the following events with their corresponding descriptions:
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What percentage of fertilized ova typically complete implantation?
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The embryo’s head and trunk develop before its limbs.
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How long does it take for the zygote to journey through the fallopian tube to the uterus?
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What will the ectoderm develop into?
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The endoderm develops into the nervous system.
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What is the function of the amniotic cavity?
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The ___ carries nutrients and wastes between the mother and the embryo.
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Match the following layers with their respective developments:
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During which stage does the embryo develop organs and major body systems rapidly?
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The umbilical cord directly connects the circulatory systems of the mother and the embryo.
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What hormone does the placenta produce to support pregnancy?
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Damage to body parts and systems is most critical during the ___ trimester of pregnancy.
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What role do chorionic villi play in the embryo's development?
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Study Notes
Stages of Prenatal Development
- Prenatal development occurs in three stages: germinal, embryonic, and fetal.
- Growth and motor development follow a top-down and center-outward pattern, where the head and trunk develop before limbs, and limbs before fingers and toes.
Germinal Stage (Fertilization to 2 Weeks)
- Begins with fertilization, lasting up to two weeks; zygote undergoes rapid division and complexity increases.
- Initial rapid cell division occurs within 36 hours post-fertilization, resulting in 16 cells by 72 hours and 64 cells by the fourth day.
- The journey through the fallopian tube to the uterus takes approximately 3 to 4 days.
- The zygote transforms into a blastocyst, floating in the uterus until the sixth day, when it begins implantation.
- Only 10 to 20 percent of fertilized ova successfully implant and continue development.
- Formation of the embryonic disk occurs at the blastocyst's edge, which differentiates into three layers:
- Ectoderm: Becomes outer skin, nails, hair, teeth, sensory organs, and nervous system.
- Endoderm: Forms the digestive system, liver, pancreas, salivary glands, and respiratory system.
- Mesoderm: Develops into inner skin layer, muscles, skeleton, excretory and circulatory systems.
- Development of supporting structures includes the amniotic cavity, placenta, and umbilical cord:
- Amniotic sac: Fluid-filled membrane that protects the embryo and allows movement.
- Placenta: Facilitates nutrient and waste exchange; supports pregnancy through hormone production and immunity to diseases.
- Umbilical cord: Contains embryonic blood vessels to transport oxygen and nutrients from the placenta and eliminate wastes.
Embryonic Stage (2 to 8 Weeks)
- Lasts from approximately 2 to 8 weeks; organs and major body systems (respiratory, digestive, nervous) develop rapidly.
- This critical period poses significant vulnerability to destructive influences in prenatal development.
- Body parts and systems are most susceptible to damage during rapid development, particularly in the first trimester.
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Description
This quiz explores the three critical stages of prenatal development: germinal, embryonic, and fetal. It covers the transformation of the zygote into an embryo, and how development continues according to specific growth patterns. Understanding these stages is essential for grasping human development from conception to birth.
