anp lab2

  1. first trimester
    • the inital period of embryological and fetal development
    • by the end of this first three months all of the organs systems have rudimentarliy developed.
    • four major events occur during the first trimester
    • -cleaveage
    • -implantation
    • -placentation
    • -embryogeneis
  2. cleavage
    • when the secondary oocyte is fertilized it becomes a single cell that is acalled the zygote
    • the zygote then undergosed a series of subdivisions
    • these subdividons reduce the amount of cytoplasm in the cells, which are called blastomers
  3. blastomeres
    subdivide for about three days to form a solild ball of celles called the morula
  4. morula
    reaches the uterus about day four and during the next two days it develops inot a hollow ball of cells called the blastocyst
  5. blastocyst
    • is composed of two cell layers
    • the outher layer develops into the placenta
    • the cells of the inner layer are clustered at on end of the blastocyst. and eventually develop inot the embryo
  6. implantation
    • occurs when the blastocyst becomes embedded in the endometrium of the mothers uterus.
    • the outer cell layer becomes intimately associated with the maternal circulatory system for nutrient and gas exchange.
    • meanwhile the inner cell layer of the blastocyst also differentiates
    • the inner cell lay becomes detached form the outer cell layer
    • the separtation yeilds a fliuid filled cavity called the amniotic cavity
    • by the twelfth day a third cell layer develops and the blasotcyst become a struture called the gastrula
    • during gaturaltion three germ layers form that five ries to the various organs systems
    • -ectoderm
    • -mesoderm
    • -endoderm
    • these three germ layers form a sheet of cells called the embryonic disk
    • and these three germ layeres then develop into the four extaembyonic membranes
    • and these membrans protect the embryo
  7. yolk sac
    • this sac is a pouch formed from the endodem and mesderm.
    • it is an intital site of blood cell formation
  8. amnion
    • this membrane is formed from the ectoderm and mesoderm
    • it lilnes the innersurface of the amniotic cavity
    • the fluid contained within the cavity is called the amniotic fluid
    • the amnion and the amniotic fluid surround and protect the growing embryo
  9. allantois
    • this membrane is forme from the endoderm and mesoderm
    • it eventually gives rise to the¬†urinary bladder
  10. chorion
    • this membrane is formed from the mesoderm and the outer cell layer of the blastocyst
    • the chorion differentiates into the featl portion of the placenta as the embryo enlarges
  11. placentation
    is the development and differentiaiton of the featal and maternal portions of the placenta
  12. chorionic villi
    • fingerlike projections that chorion devlopes
    • which make contact with the endometruim
  13. endometruim
    • as the placenta enlarges it creates a large bulge on the surface of the endometrium
    • blood ruputured maternal blood vessels slowly leaks through small chambers in the materanl placenta called lacunae
  14. embryogenesis
    • the differentation of the nbody of the embryo and the rudiimentary development of the organ system
    • the body of the embryo begins to emereg from the embryonic disk, and devlops into a bulge that has head and tail folds
  15. second and third trimesters
    • the fetus gains weight and the organ systems continue to devleop
    • by the end of the pregnacy th uteus with the fetus occupy a large portion of the materanl abdominal cavity. s
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anp lab2