Distribution of mucous blands in the foetal eustachian tube.

Abstract

The object of the study was to elucidate the topography of the mucous glands of the Eustachian tube. 47 tubes from 33 foetuses aged 11–27 menstrual weeks were freed in toto and stained by the PAS, PAS-Alcian blue, or osmium tetroxide whole-mount method. In all tubes all glands were counted and examined, and separate gland counts weret made for each part of the tube. In the 27th menstrual week there are 86 glands in the tube, 50 of which are in the pharyngeal quarter and 36 in the second (Fig. 6). The glands extend to the middle of the tube, and there are no glands in its bony part or in the middle ear. In the medial wall there is an average of 46 glands and in the lateral wall 40 (Fig. 7). The density of glands is greater in the pharyngeal quarter than in the second quarter. The density varies in the roof and floor of the tube. In the floor there are only a few glands, and their density is greatest in an area in the middle of the lateral and medial wall. Towards the roof the density decreases, and in the roof there are no glands (Figs. 3–5). The distribution and situation of the gland mass differs in the medial and lateral wall: In the medial wall the gland layer is as a whole thicker and better developed, the glands are larger and have grown deeper down into the submucosa than in the lateral wall (Figs. l and 2). The glands in the medial wall are long and have long, oblique excretory ducts. In the lateral wall the glands are flat, round, situated immediately beneath the mucosa, and have a short, tortuous excretory duct. Differences in the situation and shape of the glands are due to anatomical differences between the two walls. The distribution, situation, and shape of the glands depend upon the space available to them during their development. In the medial wall the space relations are favourable, while in the lateral wall there is immediately beneath the mucosa a firm fibrous tissue on which the fibres from the tensor veli palatini muscle insert.