Development of Muscle Fibers in the Fetal Pig

Abstract

Prenatal development of muscle fibers was examined cytochemically in the fetal pig. Fibers which are to become β fibers are observed prior to the appearance of α fibers. As was observed in the fetal lamb (Ashmore et al., 1972) the β fibers appear to act as a structural framework upon which a fiber development subsequently occurs. It is suggested that a) selection pressure for muscularity could prolong, or increase the rate of a fiber formation during the later stages of fetal development, b) that additional increases in the number of α fibers may be reflected in an increase in the αW fiber population and c) that the central location of “red” fibers in fasciculi of mature pig muscles is explained by the pattern of fiber type development in the fetus. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science.