Muscle fibre typing in the human pharyngeal constrictors and oesophagus: the effect of ageing.

Myosin-ATPase fibre typing revealed type 1 predominance (81%) in the human oesophagus and type 2 predominance in the pharyngeal constrictor (33% type 1) indicative of widely different functions. Fibre diameters were around 30 microns, significantly smaller than skeletal muscle. No significant change in mean fibre diameter or percentage of fibre type was seen with ageing, but atrophy and compensatory hypertrophy led to an increased variability in fibre diameters with age. No sex differences were observed, probably reflecting a similar usage of these muscles and contrasting with skeletal muscle.