Variations in the distribution of motor end‐plates in the avian pectoralis
- 1 January 1993
- journal article
- research article
- Published by Wiley in Journal of Morphology
- Vol. 215 (1), 65-88
- https://doi.org/10.1002/jmor.1052150105
Abstract
Most avian muscles consist of serially arranged, overlapping fibers that do not extend the length of the muscle. This condition appears to be plesiomorphic with respect to diapsid reptiles. The presence of this serialfibered architecture is evidenced by bands of stained motor end-plates (meps) perpendicular to the columns of fibers and dividing each column into a series of “segments.” The avian pectoralis was chosen for a study of variation in the distribution of meps within a single muscle. We report the interspecific variation for 158 specimens in 63 species. We also use additional specimens to examine intraspecific variation. Setting aside hummingbirds, which have an unique and clearly derived condition, the number of mep bands along a column of fibers near the shoulder falls within a remarkably small range. The number of segments is not obviously related to phylogenetic relatedness or to any characteristic of flight or ecology and is only slightly related to size. The largest specimens do average more segments per column, but there are no trends among small to medium-sized species, suggesting that there is an upper limit to fiber length. However, the shape of the sternum and pattern of connective tissue in the pectoralis alleviate the need for additional fibers in many large birds. These findings suggest that the architecture of the avian pectoralis is subject to some as yet unexplained selection that stabilizes the number of myofibers and/or motor neurons. The findings provide few clues as to whether the significant factors are phylogenetic, functional, ontogenetic, or some combination of these.Keywords
This publication has 31 references indexed in Scilit:
- "On the merits of adequacy"American Journal of Science, 1993
- The composite structure of quail pectoralis muscleJournal of Morphology, 1992
- Dynamic shape of tapered skeletal muscle fibersJournal of Morphology, 1991
- Interfiber tension transmission in series‐fibered muscles of the cat hindlimbJournal of Morphology, 1990
- Architecture of chicken muscles: short-fibre patterns and their ontogenyProceedings of the Royal Society of London. B. Biological Sciences, 1990
- Neuromuscular relationships in a muscle having segregated motor endplate zones. I. Anatomical and physiological considerationsJournal of Comparative Neurology, 1986
- The avian pectoralis: histochemical characterization and distribution of muscle fiber typesCanadian Journal of Zoology, 1986
- THE LENGTH AND MODE OF TERMINATION OF INDIVIDUAL MUSCLE FIBRES IN THE HUMAN SARTORIUS AND POSTERIOR FEMORAL MUSCLESCells Tissues Organs, 1962
- UNTERSUCHUNGEN ÜBER DIE SKELETMUSKEL-SEHNENVERBINDUNG. III.Cells Tissues Organs, 1960
- ZUR LAGE DER MOTORISCHEN ENDPLATTEN IN DEN SKELETMUSKELNCells Tissues Organs, 1957