A comparative study on the ultrastructure of the genioglossus muscle of chameleo chameleo and Bufo regularis

الملخص EN

The fibres in the genioglossus muscle of the Chameleo chameleo and Bufo regularis are similar in structural characteristics to fast fibres.

However, they reveal differences which include sarcomere lengths, myofibrillar diameters, triadic disposition, and number of triads per unit length of myofibril.

The components of the sarcomere in the lizard and the toad show extensive tubular elements of the sarcoplasmic; the regular distribution of the triads near the Z-lines is prominent and the presence of the M-bands is evident.

The myofibres contain a well-developed sarcoplasmic reticulum.

Moreover, the transverse tubular system forms longitudinal extensions along the myofilaments, thus making triadic contacts with calcium storing cisternal elements of the reticulum which intemately surround the myofibrils along the entire sareopere length.

Therefore, the organization of the myofibrils and the membranous system of the sarcoplasmic reticulum explains the release of calcium and the spread of the excitatoiy impulse intera-cellularly with great rapidity as in fast fibred muscles.