Fig. 2. Restoration of chondrocyte morphology and perichondrium growth in the humerus of the DKO embryo at E18.5. (A-C) Low-magnification images of Hematoxylin and Eosin stained sections from the wild type (A), Ihh^-/- (B) and DKO (C) embryos. Red arrows indicate the entire growth region. Green and black arrows (A,C) mark the non-hypertrophic, and the hypertrophic regions, respectively. Asterisks indicate areas of vascularization. Rectangle boxes of different colors identify various areas shown at a higher magnification below. (D1-D3,E1-E3,F1-F3,G1-G3) Images at a higher magnification of areas in A-C that are boxed in different colors: green, red, blue and black respectively. Red and green arrows (F1,F3,G1-G3) indicate cuboidal and elongated cells, respectively. Double-headed arrows (F1-F3) indicate width of perichondrium. C (F1-F3), chondrocytes; M (F2,G2), muscle. Yellow contours (F1,G1,G3) indicate the bone collar. Green lines (G1-G3) demarcate the outer layers of the perichondrium. Asterisks (G2,G3) indicate areas of vascularization.