In ten normal eustachian tubes, the intra-epithelial glands were studied quantitatively. Solitary, round intra-epithelial glands consist of 20 to 50 mucous cells, surrounded by supporting ciliated cells. Elongated streak-shaped glands may be up to 1 mm in length and are composed of several solitary glands. Gland distribution is irregular, being either solitary or in islets or major areas where density is up to 200 glands per square millimeter. The total number varies widely, being usually between 200 and 400. The number of intra-epithelial glands decreased greatly in the tympanic direction. Secretory capacity of intraepithelial glands, compared with that of goblet cells, is very slight, one four-hundredth to one one-hundred-sixtieth. Intra-epithelial glands are presumably a normal component of the tubal epithelium, but high gland count may be caused by previous abnormal stimulus of the mucosa.
Tos M, Bak-Pedersen K. Intra-epithelial Glands in Human Eustachian Tube. Arch Otolaryngol. 1972;96(6):546–552. doi:10.1001/archotol.1972.00770090824009
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