ch 22 pt 3

• what are the 3 major accessory organs that develop caudal to the stomach?

  liver, pancreas, and gallbladder
• what does the mesoderm (blood vessel endothelial cells) induce?

  the gut tube to produce the liver primordium and the pancreatic rudiments
• hepatic diverticulum: 


  liver precursor, a bud of endoderm that extends out from the foregut into the surrounding mesenchyme
• where is the hepatic diverticulum located and where does it originate from?

  originates from two populations of cells: a lateral group that forms liver cells and a ventral-medial endoderm cells that form several midgut regions
• the pancreas develops from the fusion of what?

  distinct dorsal and ventral diverticula
• why does the liver form anteriorly and below the region of the notochord?

  the notochord blocks liver formation
• what is secreted (and where) that induces liver formation? the heart and endothelial cells have a specific function which is?

  FGFs (in cardiogenic mesoderm) and BMPs (septum transverse mesenchyme) are secreted; they help induce the formation of the liver bud by secreting paracrine factors
• what is the embryonic role of the liver?

  major site for blood formation
• why is the formation of the pancreas said to be the "flip side" of liver formation?

  notochord may actively promote pancreas formation while the cardiac cells block it
• what is the role of sonic hedgehog (shh) in pancreas formation?

  Shh expression gets repressed in the dorsal endoderm; expressed throughout the gut endoderm except in the region that will form the pancreas
• what happens if blood vessels are removed from (gut endoderm?)

  the pdx1 and ptf1a- expressing regions fail to form and the pancreatic endoderm fails to bud
• how was diabetes cured in mice?

  they found the right sequence of conditions to induce the formation of functional insulin-secreting pancreatic B-cells that were able to cure diabetes in mice
• biliary atresia?

  condition in which the bile ducts of the gallbladder are blocked for reasons we do not understand
• name the teratogenic toxin that was found specially to interfere with gallbladder development. exposure to this compound does what? what is the proposed mechanism of toxicity?

  • biliatresone
  • ocluded the developing bile ducts
  • works by reducing the levels of gluthione in the cell