Tympanic membrane

Last revised by Yoshi Yu on 10 Oct 2023

The tympanic membrane is a thin membrane that separates the external ear from the middle ear. It acts to transmit sound waves from air in the external auditory canal (EAC) to the ossicles of the middle ear.

The tympanic membrane is shaped like a flat cone pointing into the middle ear. The deepest point at the center of the concavity is called the umbo

It consists of three layers (from external to internal):

  1. outer epithelial layer: stratified squamous epithelium continuous with the skin of the external auditory canal 4

  2. middle fibrous layer (lamina propria): fibroelastic connective tissue containing blood vessels and nerves of the tympanic membrane 4

  3. inner epithelial layer: non-keratinized simple cuboidal epithelium continuous with the mucosa of the middle ear 4

It attaches to a horseshoe-shaped incomplete bony ring along the wall of the external auditory canal, the tympanic annulus. The incomplete nature of its attachment results in two distinct portions of the membrane:

  • pars tensa: the larger tense portion of the membrane surrounded by the annulus, which extends from the anterior and posterior malleolar folds at the level of the lateral process of the malleus to the inferior edge of the membrane

  • pars flaccida: the smaller flaccid portion of the membrane where the annulus is deficient at the notch of Rivinus; it is located above the anterior and posterior malleolar folds 

It is anatomically separated into four quadrants by drawing an imaginary straight line continuing from the manubrium to the tympanic edge and another straight line at the umbo perpendicular to the first line 4. The four quadrants are:

  • anterosuperior

  • anteroinferior

  • posteroinferior

  • posterosuperior

This is important because vessels and nerves (specifically the chorda tympani nerve) pass through the superior portion of the membrane. Additionally, the light reflex (cone of light) is specific to the anteroinferior portion of the membrane. Thus, when intervention is performed, the posteroinferior portion of the membrane is chosen.

The membrane has two distinct nerve supplies based on the different embryological origins of the internal and external surfaces.

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Cases and figures

  • Figure 1: external ear anatomy (CT)
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  • Figure 2
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  • Figure 3
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  • Figure 4
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  • Figure 5: anatomy of the inner ear
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  • Figure 6: tympanic membrane in sound conduction
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  • Figure 7: middle ear anatomy illustrations
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