Growth of the foetal Eustachian tube and its dimensions.

Abstract

In a study of the growth and dimensions of the Eustachian tube, 47 tubes from 33 foetuses varying in age from the 12th to the 27th menstrual week were removed in toto, stained with PAS, PAS-alcian blue, and the osmium tetroxide whole-mount method. At the beginning of the 12th menstrual week the tube is 2.4 mm in length, at the beginning of the 27th week 12.5 mm. The rate of increase in tubal length is at a maximum from the 20th to the 27th week, amounting to 0.8 mm per week. Later, the weekly increment is presumably only 0.6 mm. The mean inner circumference of the tube is 1.0 mm at the beginning of the 12th week and 4.4 mm at the beginning of the 27th week. The mean diameter of the tube is 0.32 mm at the beginning of the 12th week and 1.38 mm at the beginning of the 27th week. Up to the 15th week the tube is almost round in cross section, but as cartilage develops it becomes first oval and, in the 27th week, slit-shaped.