Week 5 -notochord and somites and ectoderm

• What does the notochord become eventually

  Nuclei pulpus (part of intervertebral discs)
• Dermatome forms

  Dermis of back
• What organs the intermediate mesoderm form?


  Kidney and gonads
• What does the lateral plate mesoderm form?

  Splanchnic, somatic, extra-embryonic
• Function of oligodendrocytes


  Myelinate axon
• Function of astrocytes 


  Support neurons in many ways
• How is the neural plate induced to be different to surrounding tissues

  Morphogen gradient, signalling
• How does neural plate become the neural tube?


  Neurulation- folding plate to become hollow neural tube
• What happens if neuropore remains Open?

  Neural tube defect, bottom: spinal bifida, top: anencephaly
• What is the space inside the brain


  Fluid filled space called vesicles but becomes ventricles in later life
• Signals from what tissues pattern the dorsoventral axis of the spinal cord?

  Notochord and epidermis releasing sonic hedgehog and BMP
• What types of proliferation occur in neurogenesis?


  Symmetrical and then asymmetricak type 1 and asymmetrical type 2
• What factors affect asymmetrical proliferation?


  Extrinsic signals, contact dependent lateral inhibition (no you can’t become this), plane of division.
• Where do neuroblasts move after they are generated?

  Radially to the cortex
• Zones of spinal cord as it develops

  ventricular layer, mantle layer or intermediate zone, marginal zone.
• Roles of the notochord?

  patterning the neural tube mainly via sonic hedgehog pathway and reinforcement and maintenance of events begun during gastrulation: left right asymmetry, cardiac and pancreatic development
• Around day 19-21 of human embryonic development what happens in development of the notochord?


  Cells that enter primitive streak at primitive node migrate cranially to form chordal process. It grows longer through cell proliferation to form prechordal plate.
• what happens at day 20 and between day 22-25 of human embryonic development for notochord?

  Day 20: chordal tissue forms chordal plate by binding with endoderm and breaks away

  day 22-25: chordal tissue breaks away from endoderm and ectoderm to form notochord

  day
• What does the paraxial mesoderm develop into? Different stages?


  Become somites which extends cranially. Responsible for segmentation of embryo. What they become depends on where they are. But these have precursor cells for sclerotome (axial skeleton), myotome (muscle of neck, trunk, extremities), dermatome (subcutaneous tissue and skin)
• What signalling determines placement of somite formation?

  Notch signalling
• Which signal specifies similes along posterior anterior axis?

  HOX GENE OATTERNING
• How many somite pairs in humans?

  42-44 but in the end 35-37
• Somite fates?


  Sclerotome: vertebrae and rib cartilage, myotome: muscle or back, limbs and ribs, dermamyotome: forms dermis of back
• What does the intermediate mesoderm form?

  Kidney and somatic cells of gonads
• What does lateral plate mesoderm form!

  Somatic mesoderm (closest to ectoderm) forms lateral and ventral walls of embryo

  splanchnic mesoderm (closest to endoderm): wall of GIT

  extraembryonic
• Cells of CNS?

  Neurons and Glial cells (astrocytes, oligodendeoxytes, ependymal cells, microglia (immune cells)
• a single oligodendrocyte myelinated multiple segments or axons, true or false?

  True
• astrocytes functions?


  Nutrient supply to neurons

  clean up at sunapse

  phagocytose cell debris

  structural role
• What does the ectoderm form?


  Neural plate, neural crest, placodes, skin hair and nails

  
• How does ectoderm form nervous system?

  during gastrulation: neural induction to form neural plate

  Neurulation: neural tube
• How is neurulation an example of morphogenesis?

  Apical constriction of actin filaments help drive elevation of neural folds. Differential expression of Cadherin help separation of neural tube from epidermal ectoderm
• What type of signalling in patterning of CNS?

  Paracrine
• Spinal cord patterning signalling?

  Shh produced from notochord going from ventral. Also fgf, bmp
• Proliferstion in neuron


  symmetrical proliferation then asymmetrical then continue neural progenitor cell pathways using intrinsic and extrinisc signals
• Which direction does paradisal mesoderm elongate in embryogenesis?

  Cranial caudal
• Why do germ cells not go through gastrulation?

  maintain pluripotent
• What factors affects asymmetrical proliferation?

  Extrinsic signals, contact dependent lateral inhibition, plane of division (inherit different parts of cytoplasm=different factors)