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Development

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Recognize the germ cell layers from which different tissues ... tissue growth, folding. programmed cell death sculpts body parts. Organogenesis. Morphogenesis ... – PowerPoint PPT presentation

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Title: Development


1
Development
  • Chapter 37

2
Objectives
  • Be familiar with the early stages of animal
    development
  • Recognize the germ cell layers from which
    different tissues develop and the organs that
    result from those layers

3
What happens AFTER fertilization
  • Fertilization results in the union of the egg and
    sperm nuclei resulting in a diploid cell (Zygote)
  • Zygote undergoes Mitosis to increase cell numbers
  • Between mitotic events there is no increase in
    cell size (resulting in smaller cells)

4
Cleavage
  • During cleavage the cytoplasm pinches in with
    the
  • help of microfilaments
  • divides egg cytoplasm into numerous smaller
    cells
  • called Blastomeres

5
  • cleavage increases the number of cells but not
    the
  • overall volume of the egg

...
  • Different daughter cells receive different
    regions of
  • the cytoplasm depending on where they form
  • Therefore, they end up with different bits of
    information
  • and the descendants of those cells develop
    differentially

6
Stages of Cleavage (in the mammalian egg)
Early cleavage
Late cleavage
Blastula hollow ball of cells surrounding a
fluid filled cavity
Blastomeres surround a fluid-filled cavity
called the blastocoel
7
Gastrulation
  • cellular organization, invagination
  • newly formed cells become arranged into
    different
  • germ layers

1. Ectoderm
  • outermost layer
  • nervous system, outer layer of skin

2. Mesoderm
  • middle layer
  • muscle, skeleton, circulatory, reproductive,
  • excretory, connective tissues

3. Endoderm
  • innermost layer
  • inner lining of gut and associated organs

8
Blastula
Early gastrula
Late gastrula
Cell differentiation occurs during gastrulation
9
Organogenesis
Primary tissue layers give rise to groups of
cells unique in structure and function (organs)
Morphogenesis
  • cell division
  • cell migration
  • tissue growth, folding
  • programmed cell death sculpts body parts
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