Topic E3 Flashcards

1
Q

Define cell potency:

A
  • The ability for a cell to differentiate into different cell types
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2
Q

What are the 4 supportive membranes associated with amniotic vertebrate embryonic development?

A
  1. Amnion: encloses amniotic fluid which protects the embryo
  2. Chorion: gaseous exchange
  3. Allantois: holds nitrogenous wastes, contributes to gas exchange
  4. Yolk sac: nutrition source in egg laying amniotes
  • in humans the yolk sac and allantois are incorporated into the umbilical chord
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3
Q

Describe the process by which a zygote becomes a blastocyst

A
  • The zygote undergoes cleavage: a period of rapid cell division without growth in overall size of the embryo
  • Once the embryo reaches the 8 cell stage it undergoes compaction- the cells become tightly joined
  • The morula forms- inner and outer cells of embryo are defined
  • The blastocyst forms- the inner cells move to one side of the embryo and a cavity forms
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4
Q

How are cells of the early blastocyst divided into trophoblast and hypoblast?

A
  • This is determined by the contact the cell has with other cells on all sides (or lack thereof in trophooblast cells) causes the cells to express different factors
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5
Q

What factors to outer early blastocyst cells express?

A
  • Cdx2 (which inhibits expression of Nanog and Oct4)

- they become trophoblast cells

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6
Q

What factors to inner early blastocyst cells express?

A
  • Oct4, Nanog and Gata6= pluripotency factors

- they become inner cell mass cells

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7
Q

How does the inner cell mass divide into epiblast and hypoblast?

A
  • Inner cell mass cells that express Nanog will become epiblast
  • Inner cell mass cell that express Gata6 will become hypoblast
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8
Q

What is gastrulation?

A
  • The formation of the 3 primary germ layers (ectoderm, mesoderm and endoderm) from the bilaminar disc
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9
Q

Explain the process of gastrulation:

A
  • Epiblast cells migrate through the primative streak and displace the hypoblast forming the definitive endoderm
  • More epiblast cells follow these migrating cells and form a middle layer creating the mesoderm
  • the epiblast becomes ectoderm
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10
Q

What is the fate of the trophoblast?

A
  • to form extraembryonic tissues such as the foetal part of the placenta
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11
Q

What is the fate of the epiblast?

A
  • To form the embryo (3 germ layers) and amnion
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12
Q

What is the fate of the hypoblast?

A
  • To form part of the yolk sac
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13
Q

What is regulative development?

A
  • The ability of early mammalian embryos to produce a normal and complete organism even if cells are removed or added
    e. g. an early embryo can split and both halves can form complete embryos- identical twins
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14
Q

What are some examples of ectoderm derived tissues?

A
  • Epidermis
  • Nerves
  • Neural crest cells
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15
Q

What are some examples of mesoderm derived tissues?

A
  • Bones and muscles
  • Circulatory system
  • Gonads
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16
Q

What are some examples of endoderm derived tissues?

A
  • Epithelial lining of GI tract and associated organs
  • Epithelial lining of respiratory ducts
  • thymus
17
Q

What is organogenesis?

A
  • The differentiation and organisation of tissues from the 3 germ layers and their arrangement into organs
  • Most organs are comprised of contributions from all 3 germ layers
18
Q

What are the 2 key organisers in the early mammalian blastocyst?

A
  1. Specialised group of cells in the hypoblast- anterior ventral endoderm (AVE)
  2. Primative streak
19
Q

How does the primative streak form?

A
  • BMP4 of extraembryonic origin is secreted to the epiblast which instructs it to make Wnt and Nodal signalling molecules
  • The AVE is at the anterior end and instructs the anterior epiblast to make Lefty and Cerberus signalling molecules that inhibits Wnt and Nodal production
  • This means that the primative streak forms at the posterior end where Wnt and Nodal are expressed fully
20
Q

What is neuralation?

A

The process of neural chord formation from ectoderm (neural plate) down the anterior-posterior axis - Neural chord induction is initiated by the underlying notochord sonic hedgehod signalling