Tympanic Membrane Structure
The tympanic membrane consists of three distinct layers: an outer ectodermal (epithelial) layer, a middle fibrous connective tissue layer (lamina propria), and an inner mucosal (endodermal) layer. 1
Layer Composition and Organization
The three-layer architecture forms a thin sandwich structure that separates the external ear from the middle ear 1:
Outer layer (ectodermal): Composed of stratified squamous epithelium continuous with the ear canal skin, this layer undergoes soft keratinization with structural proteins including cytokeratins, filaggrin, involucrin, and loricrin 2
Middle layer (lamina propria): The fibrous connective tissue layer contains an unusual collagen composition with predominantly type II and type III collagen, plus a small amount of type I collagen 3. This unique collagen arrangement is responsible for the distinctive physical properties and mechanical behavior of the tympanic membrane 3. The middle layer also receives contribution from neural crest-derived fibroblasts and mesoderm-derived vasculature 1
Inner layer (mucosal): An endoderm-derived mucosal epithelial layer continuous with the middle ear mucosa 1, 3
Clinical Relevance
Understanding this three-layer structure is essential when examining the tympanic membrane for pathological changes 4:
- Chronic negative middle ear pressure can weaken the lamina propria, leading to retraction pockets and atelectasis 5
- Inflammatory mediators in chronic otitis media with effusion (including mucin, leukotrienes, prostaglandins, and cytokines) can cause reactive changes in the tympanic membrane structure 4
- During perforation repair, the ectodermal layer retracts first, then proliferates and migrates to bridge the gap, followed by mesenchymal and mucosal layer repair 1