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. Author manuscript; available in PMC: 2015 Apr 1.
Published in final edited form as: Semin Cell Dev Biol. 2007 Feb 20;18(2):255–266. doi: 10.1016/j.semcdb.2007.02.005

Fig. 2.

Fig. 2

Formation of appendages. (A) Embryonic feather morphogenesis. Molecules which affect major events along the progression to successive stages of feather development are shown. Proliferative cells are indicated in blue with darker shades indicating areas of higher proliferation. Proliferation starts at the feather tip but recedes down toward the feather base as morphogenesis proceeds. The plane on the right most feather shows the height from which the adjacent cross section was taken to show barb ridge (red arrow) and rachis (red arrowhead) formation. AP-axis: anterior–posterior axis; P-D axis: proximal-distal axis. (B) Embryonic mammary gland morphogenesis. Key stages in mammary gland development are shown. Known molecules which regulate each morphogenetic step are presented. The legend identifies the tissues shown in the schematic. Modified from [32].