Systematic distribution of muscle fibre types in the rat and rabbit diaphragm: a morphometric and ultrastructural analysis
Kilarski, W.; Sjöström, M.
Journal of Anatomy 168: 13-30
1990
ISSN/ISBN: 0021-8782 PMID: 2139020 Document Number: 360959
The histochemical and ultrastructural characteristics of the adult rat and rabbit costal diaphragm were investigated. On the basis of enzyme histochemistry, the rat diaphragm was found to contain 42% and 39% type I, 24% and 25% type IIA, and 33% and 34% type IIB fibres on the thoracic and abdominal surfaces respectively. The rabbit costal diaphragm contained 18% and 26% type I, 46% and 39% type IIA, and 35% and 34% type IIB fibres on the thoracic and abdominal surfaces respectively. Differences in the proportion of each muscle fibre type were also observed between diaphragm regions (ventral, medial, and dorsal) in the rat as well as in the rabbit. Differences in muscle architecture were also pointed out on the basis of stereological analysis in estimation of volume density, surface density, numerical density, and cross-section areas of each muscle fiber type. The fine structural analysis of all three fibre types also showed significant differences in the width of the A-bands, and Z-lines between the muscle fibre types of the rat and rabbit costal diaphragm.