ch 22 pt 4

• what are the lungs derived from?

  digestive tube
• laryngotracheal groove-


  an outpouching of endodermal epithelium in the center of the pharyngeal floor, between the 4th pair of pharyngeal pouches that extends ventrally
• what does the laryngotracheal groove bifurcate into?

  branches that form the paired bronchi and lungs
• what is a tracheal-esophageal fistula?

  connection between gut tube and the respiratory tube
• what has to be blocked in order to specify the epithelium of the esophagus ?

  wnt activity
• what is the role of the transcription factor barx1 in the differentiating the esophagus and trachea?

  produces the wnt-blocking soluble frizzled-related proteins (SFRP)
• is the 3D branching pattern of the mammalian lung "random"?

  no
• what are the 3 different modes of bronchial epithelial branching?

  1. domain branching
  2. planar bifurcation
  3. orthogonal bifurcation
• how do we know that smooth muscle is involved in forcing the bifurcation of the mouse lung?

  pharmalogical disruption of the differentiation prevents terminal branching
• How is the process different in birds in regards to bifurcation?

  branch points are built off of a parental branch by triggering localized apical constriction which forces a new bud to form (cell shape change that promotes tissue remodeling)