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What is a Tympanic Membrane?
The tympanic membrane, also known as the eardrum, is a thin membrane between the middle and external ear. It is a cone-shaped structure that is found in humans as well as several tetrapods. It transmits sound vibrations from outer air to the ossicle in the middle ear and then to the cochlea.
Structure of the Tympanic Membrane
- The tympanic membrane is made up of three layers:
- The outer surface is lined with stratified squamous keratinised epithelium, which continues with the epidermal layer of the external auditory canal.
- The inner surface comprises a simple cuboidal epithelium, which continues with the epithelial surface of the tympanic cavity.
- The middle layer, also known as lamina propria, is a fibrous layer of fibroelastic connective tissue. It houses the nerves and blood vessels of the tympanic membrane.
- The fibrous layer is thickened at the interior end of the tympanic membrane and forms a rigid ligamentous ring.
- The handle of the malleus (one of the three ear ossicles) remains attached to the middle layer of the tympanic membrane. It pulls the inferior and anterior portions of the membrane, giving it a conical shape.
- The deepest depression of the structure is called the umbo.
- The eardrum is divided into two regions: the pars tensa and the pars flaccida.
Difference between Pars Tensa and Pars Flaccida
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Pars tensa is the larger portion of the tympanic membrane that remains stretched to a maximum. |
Pars flaccida is the smaller of the tympanic membrane that remains less taut. |
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It is made up of organised circular and radial fibres. |
It is made up of loosely arranged elastic collagen. |
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It is well vascularised. |
It lacks blood vessels in significant portions. |
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None or very less |
Numerous mast cells are found in the pars flaccida. |
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It is thinner and rigid. |
It is thicker and more elastic. |
Function of Tympanic Membrane
The tympanic membrane plays a crucial role in sound amplification and transmission. As soon as the tympanic membrane senses a sound, it transmits the signal to the ossicles in the middle ear, which ultimately gets passed on to the cochlea in the inner ear.
Clinical Significance
The tympanic membrane is prone to unintentional rupture pertaining to incidents such as swimming, martial arts, diving, blast injuries, and air travel. In these conditions, the upper respiratory tract of the person is congested, which prevents equalisation of pressure in the middle ear.
Symptoms of this eardrum rupture include vertigo, tinnitus and hearing loss.
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