Ultrastructure of the Secondary Tympanic Membrane in the Human Fetus
作者:
Yan Shidu,
Qiu Zhimin,
Zhou Ningshen,
期刊:
Cells Tissues Organs
(Karger Available online 1988)
卷期:
Volume 131,
issue 4
页码: 332-337
ISSN:1422-6405
年代: 1988
DOI:10.1159/000146536
出版商: S. Karger AG
关键词: Membrane;secondary tympanic;Fenestra rotunda membrane;Development
数据来源: Karger
摘要:
The normal secondary tympanic membrane in human fetuses was examined by transmission electron microscopy. The membranes in 5- to 9-month-old fetuses consist of the following three layers: (1) an outer squamous epithelial layer facing the middle ear, which is not formed until 4 months old; (2) a middle fibrous layer containing collagen, elastin, fibroblasts and fibrocytes, and (3) an inner layer of flat cells facing the scala tympani. Following the maturation of the fetus the epithelium is getting thinner and fibroblasts are reduced in number, but fibrocytes are increased and collagen and elastin grow gradually in density. The ultrastructure of the secondary tympanic membrane at 8 month is mature in type and shows the same characteristics as in the adult.This membrane has an important and complicated physiological function. The epithelium of the outer layer, with tight junctions and multiple desmosomes, provides a barrier to keep harmful substances out. The stability of the membrane provides protection against rupture, while the elasticity plays a role in the physiology of hearing as well.
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