Tympanic membrane

  • The tympanic membrane (also known as eardrum, myringa, membranous wall of tympanic cavity, latin: membrana tympanica) is a cone-shaped thin membrane at the end of the external acoustic meatus, which separates the external ear from the middle ear.

    The tympanic membrane contains fibrous connective tissue that is covered with skin externally and lined by mucosa internally, where the membrane projects to the tympanic cavity of the middle ear, forming the membranous or lateral wall of the tympanic cavity. Attached to the inner surface of the eardrum is one of the auditory ossicles, the malleus, which is connected on the other side with the next ossicle, the incus.

    There are two areas of the tympanic membrane called the pars flaccida and the pars tensa. The pars flaccida is the smaller, more flaccid part of the tympanic membrane in its upper region, while the pars tensa is the largest part of the tympanic membrane situated within a fibrocartilaginous ring, called the tympanic ring. The center of the pars flaccida is drawn inward and is called the umbo. The umbo of the tympanic membrane is situated at the tip of the manubrium of the malleus, which is fused with the tympanic membrane.

    The main function of the tympanic membrane is to transfer sound waves from the air from outside, which reach the membrane through the external acoustic meatus, to the auditory ossicles in the middle ear, which then conduct the vibrations to the oval window transferring them to the fluid and membranes of the cochlea of the inner ear. Thus, the eardrum participates in converting and amplifying the vibrations in air to fluid-membrane vibrations.

    The sensory innervation of the tympanic membrane is provided by several cranial nerves. The auriculotemporal nerve, arising from the mandibular nerve (CN V3), supplies the external surface of the tympanic membrane, which also receives fibers from the auricular branch of the vagus nerve (CN X), and the facial nerve (CN VII). The inner surface of the tympanic membrane is supplied by the glossopharyngeal nerve (CN IX).