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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Curr Opin Cell Biol. 2010 Sep 9;22(5):640–650. doi: 10.1016/j.ceb.2010.08.019

Figure 3. Conserved developmental mechanisms for branching morphogenesis.

Figure 3

(A) Most mammalian epithelial tubes have a simple organization. However, during active morphogenesis both the mammary [14] and salivary [26] epithelia are multilayered or stratified. By contrast lung appears to retain a simple organization during branching morphogenesis [40]. (B) During branching morphogenesis in each of the epithelial organs there is a rich diversity of ECM proteins and stromal cell types, including diverse leukocytes and fibroblasts. Functional evidence has been provided for the importance of macrophages during mammary development [22,26], but it remains a relatively open question which stromal cell types are required for, or assist in, the normal development of the epithelial organs. ECM = extracellular matrix.