Branching determinants
_Removal
of mesenchyme halts branching
_Non
lung mesenchyme does not support branching
_Lung
mesenchyme placed in trachea or salivary gland induces specific branching
_Proximal
vs distal mesenchyme induces site appropriate epithelial cell development
_Mesenchymal
factors are diffusable across membranes – No contact needed, but gradients are very local.
_Epithelial
factors ÒcrosstalkÓ to determine mesenchymal growth and differentiation.