Histology of human eustachian tube muscles: effect of aging

Forty-eight specimens of human eustachian tube tensor and levator muscles were examined histologically in order to study their functions and the effect of aging. The muscle fibers reach their maximum growth in the third decade with a narrow short diameter: tensor 21.8 micron and levator 24.5 micron; with advancing age, they were prone to atrophy, particularly in the tensor. Three muscle fiber types, red, white, and intermediate, were identified in the tubal muscles. The white fibers predominated in the tensor, and they were a main component of muscle fibers in fetuses and elderly adults. Lipofuscins were located in the periphery of muscle fibers, dominantly in the levator, and became numerous and larger with age. Our observations suggest that 1) the tensor produces a rapid opening of the eustachian tube while the levator creates tension and dilates the pharyngeal orifice of the tube for a relatively long period, and 2) these muscle functions deteriorate with advancing age.