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15 Cards in this Set

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