Figure 1.
A schematic diagram of primary and secondary myogenesis in relation to the formation of fibre type diversity. Type I/slow myotubes are shown as light, type II/ fast myotubes are shown as dark. Muscle progenitors give rise to embryonic myoblasts which fused to form primary myotubes. Subsequently, fetal myoblasts fuse either with primary myotubes or with fetal myoblasts to form secondary fibres. Fibres formed from secondary myogenesis appear to be able to switch between the different fibre types, while type I/slow fibres formed during primary myogenesis do not. Based on Dunglison et al.41 Pin et al.42 and Stockdale.48 The contributions of former colleagues at the Rowett Institute, Aberdeen to this figure are acknowledged.