Fig. 3. Transmission electron micrograph (longitudinal section) through the tongue retractor muscle (m. hyoglossus) of an adult Pogona vitticeps. (A) Muscle in the resting condition. Note how the thin filaments almost abut in the middle of the A-band. The Z-disk is of the normal continuous type typical of vertebrate cross-striated muscle. (B) Section through a muscle in the extended condition (140% of whole muscle resting length). Note how the sarcomeres are extended to only approximately 120% of their resting length. Even in the extended condition, the overlap between thick and thin filaments is large, allowing the muscle to generate near-maximal tension. Scale bar, 1 µm.

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