Fig. 6. Defective osteogenesis in Fgfr2^cko mice. (A,B) H&E stained sections of the distal tibia of P7 mice, showing the epiphyseal growth plate. The length of the metaphysis is indicated by the double-headed arrows. (C,D) Enlarged views showing the morphology of metaphyseal osteoblasts in the proximal tibia. Note that osteoblasts are plump cuboidal cells in the wild-type mouse and become atrophic and irregular in the Fgfr2^cko mouse (arrows). (E,F) Enlarged view of the boxed regions in A and B showing the morphology of the perichondrium. The thickness of the perichondrium is indicated by double-headed arrows. (G,H) H&E stained sections showing the femoral diaphysis of P7 mice. The thickness of the cortical bone plus the periosteum is indicated by double-headed arrows. Diaphyseal lacunae occupied by active osteoblasts are indicated by arrows. (A,C,E,G) Sections from control littermates. (B,D,F,H) Sections from the Fgfr2^cko mice. Objective magnification, (A,B) 10x; (C-F) 40x; (G,H) 20x. bm, bone marrow; cb, cortical bone; fc, fibroblast-like cell layer; h, hypertrophic zone; mu, muscle; op, osteoprogenitor layer; p; proliferation zone, po, periosteum; tb, trabecular bone.