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15 Cards in this Set
- Front
- Back
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embryology
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development of a unicellular zygote into a multicellular organism through cell divisoin, cellular differentiation, and morphogenesis (differentiation into tissues)
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determinate cleavage vs. indeterminate cleavage
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cleavage whose differentiation pathways are defined early on; cleavage in which cells retain ability to develop into a full organism.
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fraternal twins are conceived when...
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following ovulation, more than one egg is fertilized in the uterus by the incoming sperm.
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identical twins are a result of
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indeterminate cleavage (when cells retain the ability to develop into a full organism)
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differentiation
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specialization of cells which occurs during the developmental stage of the organism.
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morula
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solid ball of embryonic cells, 8 cell embryo reaches the uterus and continues to divide.
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blastulation
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morula turns into blastula, first by the creation of a blastocoel, a liquid-filled cavity. the blastula is a hollow sphere of cells
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gastrulation
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blastula turns into gastrula. the gastrula has an ectoderm, mesoderm, and an endoderm. it also has an archenteron and a blastopore.
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parts of a gastrula
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ectoderm: becomes the nails, eyes, skin, nose, mouth, nervous system.
mesoderm: intestinal and respiratory tract endoderm: musculoskeletal, circulatory, and excretory system, and gonads |
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kinds of development
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external development
non-placental internal development placental internal development |
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embryonic membranes of eggs
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chorion, allantois, amnion, yolk sac
chorion: membrane closest to shell, gas exchange allantois: membrane involved in respiration and excretion amnion: sac-like membrane containing amniotic fluid, shock-absorber yolk sac: encloses the yolk (nutrients), has blood vessels that transport the nutrients to the emmbryo |
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examples of animals that develop externally
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fish, amphibians, birds, some mammals, reptiles
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non-placental internal development
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marsupials, kangaroos have their embryos develop within the body but without a placenta. the transfer of oxygen and nutrients is less effective
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placental internal development
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fetus receives oxygen through specialized circulatory system of the mother which also allows for nutrient and waste exchange. placenta and umbilical cord are outgrowths of the chorion, allantois, amnion, and yolk sac.
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childbirth
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labor: series of strong uterine contractions
1. cervix thins out and dilates 2. rapid contractions 3. uterus contracts, expelling the placenta and umbilical cord |
