Opening Mechanism of the Eustachian Tube

Abstract

In order to examine the mechanism of tubal opening in detail, the following three experiments were conducted. Experiment 1: The tensor and the levator muscle were selectively stimulated in four monkeys. Tensor stimulation produced constant tubal opening, while levator stimulation had no effect on the opening. This result indicates that the tube opens by the tensor alone. Experiment 2: Cineradiographic studies of the tube during swallowing were conducted in three patients. Motion of the tube, made visible by means of contrast medium, was filmed at a vertical angle. Frame by frame analysis of the film revealed a marked difference between movement of the tube at its pharyngeal orifice and at its cartilaginous part. The result suggested that there are two muscles which dilate two different parts of the tube. Experiment 3: Cineradiography of the tube during selective stimulation of the tensor and the levator muscles was carried out on three monkeys. Levator stimulation produced dilation of the pharyngeal orifice, but no tubal opening. On the other hand, tensor stimulation produced opening of the tube as a whole, by outward displacement of the lateral wall of the tube. It is concluded that almost the entire cartilaginous part of the eustachian tube opens by contraction of the tensor muscle, while the distal end of the tube increases in diameter by contraction of the levator, but the tube never opens as a whole by its contraction.