Flashcards in Lecture 7: Brain Development Deck (56)
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1
key developments of brain occur...
during first two month period of gestation
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fertilization
Fusion of gametes (sperm and egg)
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How does sperm fertilize an egg?
- Sperm releases enzymes that digest protein coat around egg
- Sperm head fuses to egg cell membrane
- Tail separates from head and male nucleus enlarges and travels to female nucleus for nuclei fusion
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Zona pellucida
protein coat around egg
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zygote
first cell of human body
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morula
ball of cells
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blastocyst
embryonic structure with cavity (contains fluid called blastocoele (around by day 6)
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Why is mitochondria maternally inherited?
Paternal mitochondria is housed in the tail of the sperm which is cut off (not included in zygote).
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Implantation
embedding of blastocyst into uterine lining around day 7, continuing on during day 8 and 9.
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Blastodisc
What the blastocyst divides into after implantation: inner cell mass that develops into two layers of cells (epiblast and hypoblast).
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Where does fertilization occur
in the uterine tube
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Why is the inner cell mass of the blastocyst so important?
Contains undifferentiated cells—embryonic stem cells. Limitless potential.
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When can you procure embryonic stem cells?
Before the blastodisc forms (cells have differentiated) so around day 8 or 9
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Gastrulation
Occurs around day 12. Top layer of cells (epiblast) start to migrate toward inside of embryo along linear streak called the primitive streak (ventral area) Two cells layers become three cells layers: ectoderm (outermost), mesoderm (middle), and endoderm (innermost).
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What does gastrulation determine?
Body axis
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Ectoderm
becomes nervous system and epidermis (skin)
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Endoderm
becomes GI tract, respiratory tract, endocrine glands
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mesoderm
becomes everything else (muscles, bones, cartilage, blood, blood vessels, genitourinary system).
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What happens around day 18 of embryonic development?
Patch of cells on ectoderm becomes neural plate
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What does the neural plate develop into?
The nervous system. Rest of ectoderm becomes skin.
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Which layer of cells does the notochord form from?
Mesoderm. Notochord forms under the neural plate.
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What occurs around day 20 of embryonic development?
After neural plate forms, it starts to roll up to form the neural groove which fuses to form the neural tube which becomes the brain and the spinal cord.
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What's important about the cells from the fusion site of the neural tube?
Some are pinched off and become a cluster of cells called neural crest cells (become cells in dorsal root ganglia).
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When is the neural tube formation complete?
around day 22.
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What does the cavity in the neural tube become?
The cerebral ventricles in brain and the central canal in spinal cord.
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Which part of the neural tube gives rise to spinal cord and which to the brain?
Most of tube becomes spinal cord (bottom part). Anterior portion enlarges to form three vesicles: forebrain, midbrain, hindbrain.
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What causes the neural tube to thicken?
Cell divisions
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Neural crest cells
cells that are pinched off to become dorsal root ganglia when neural tube fuses
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Neural progenitor cells
cells that become neurons and glia in neural tube. Like neural stem cells.
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