ch 20 pt 2

• what plays a role in establishing the microanatomy of the circulatory system

  chance
• what is the circulatory system development constrained by

  physiological, evolutionary & physical parameters
• blood vessel development occurs in 2 distinct processes called

  vasculogenesis and angiogenesis
• vasculogenesis


  the de novo creation of a network of blood vessels from the lateral plate mesoderm
• angiogenesis


  primary network of blood vessels created by vasculogenesis is remodeled and pruned into a distinct capillary bed, arteries and veins
• what happens during the first phase of vasculogenesis


  a combination of BMP, WNT, & notch signals activates the Etv2 transcription factor in lateral plate mesoderm cells leaving the posterior of the embryo, converting them into hemangioblasts
• Paracrine factors list & their receptors

  FGF2 with FGF2R

  VEGF with VEGFR-2, VEGFR-1 & VEGFR-1,2

  ANG1 with TIE2

  PDGF with PDGFR

  TGF-B with TGF-BR
• what is ETV2 transcription factor

  important for vessel development
• how were fluorescent probes utilized to understand pathways involved in blood cell and blood vessel specification

  to be able to make single-cell fate maps, allows you to visualize where the gene is expressed
• what is the role of Cdx4 gene in aortic progenitor cell differentiation

  induces the pathway to permit aortic cells to differentiate into hemangioblasts
• describe the role of notch signaling in modulating hemangioblast specification, what is the tole of Runx1 in these pathways

  notch regulates whether the hemangioblast becomes a blood cell precursor or a blood vessel precursor; Runx1 induces the conversion of endothelial cells to blood stem cells (notch activates runx1)
• where does the extraembryonic vascuologenesis occur

  blood islands
• what does intraembryonic vasculogenesis form


  dorsal aorta
• blood islands


  aggregations of hemangioblsts in splanchnic mesoderm
• explain the significance of endothelium-forming cells aggreagating in the yolk sac in amniote development

  because the blood islands lining the yolk sac will produce the veins that bring nutrients to the embryo and transport gases to and from the sites of respiratory exchange
• what are the 3 growth factors which are critical for initiating vasculogenesis

  • FGF2- generation of hemangioblasts from the splanchnic mesoderm
  • VEGF-directs the expansive growth of blood vessels in placenta
  • angiopoietins- mediate the interaction between the endothelial cells and pericytes
• what is the critical factor for angiogenesis

  VEGFA- induces the the migration of endothelial cells from existing blood vessels forming capillary networks there
• what factors are involved in inducing these "critical factors"

  hypoxia
• what is meant by sprouting


  forming a new vessel
• what are "tip cells" and how do they differ from other vessel cells, what do tip cells produce


  they are endothelial cells in the existing blood vessel that respond to the VEGF and sprout to form a new vessel; express the notch ligand delta-like 4 on their cell surfaces
• why do blood vessels not sprout in the cornea, how is this regulated

  to allow for transparency of cornea & optical activity; it prevents the release of VEGF and soluble VEGF receptor regulates the increased formation of vasculature in the uterus during pregnancy
• what is preeclampsia, what does it have to do with angiogenesis and VEGF


  hypertension and poor renal filtration in the mother and consequent fetal distress; if too much soluble VEGF receptor is produced normal angiogenesis may be dramatically reduced
• what could happen if too much VEGF is produced

  spiral arteries that nurish the fetus fail to form and the capillary bed of the kidneys is reduced