Prenatal Development Notes

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Prenatal Development Notes 1. Germinal Stage (conception) a. Egg and sperm form zygote b. Zygote divides and travels down fallopian tube c. Zygote becomes blastocyst (2 layers of cells encircling the hollow center) d. Blastocyst implants in uterus 2. Embryonic Stage (3-8 weeks) a. Begins when implantation is complete b. Outer layer of blastocyst creates membranes; amnion and chorion c. Placenta is fully developed and serves as liver and kidneys until they actually develop 3. Fetal Stage (8weeks-birth) a. Begins when organogenesis is complete b. Bone cells, fingerprints, and genitals form c. Organism responds to loud noises d. This stage is characterized by rapid growth Vocabulary: o Zygote- single cell (from sperm and egg) at conception o Gene- subdivision of DNA o Genotype- specific instructions in genes o Phenotype- set of observed characteristics (genotype, environment influence, and interaction of birth) o Viability- ability to live outside of the womb
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Unformatted text preview: o Fetus- name given to developing organism (from 8 weeks after conception to birth) • The nucleus of each cell has 46 chromosomes (23 pairs); not in the sperm or ovum o XX- female o XY- male o Down syndrome occurs when the fetus has three copies of chromosome 21 • What is developing: o 9-12 weeks – fingerprints, facial expressions, swallowing and “breathing” of amniotic fluid o 13-16 weeks – responds to mother’s voice and loud noises o 17-20 weeks – fetal movements can be felt by mother, heartbeat is detectable, fingernails o 21-24 weeks – viability becomes possible (most born at this time do not survive) o 25-28 weeks – recognizes mother’s voice, regular rest and activity periods o 29-32 weeks – rapid growth, fat deposited under skin o 33-36 weeks – moves to head down position, mature lungs o 37+ weeks – considered full term...
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  • Spring '13
  • KateNorthcott
  • Embryo, sperm form zygote, Zygote- single cell

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