tympanic membrane

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.

Gross anatomy

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

It attaches to an incomplete ring of bone along the wall of the EAC, the tympanic annulus. It consists of three layers (from external to internal):

  • cutaneum (skin)
  • radiatum circulare (collagen fibers)
  • mucosum (epithelium)
  • There are two distinct portions of the membrane:

    • pars tensa: the tense portion of the membrane is the larger portion and 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 flaccid portion of the membrane is much smaller and is the portion of the membrane above the anterior and posterior malleolar folds 
    Quadrant separation

    It is anatomically separated into four quadrants:

    • anterosuperior
    • anteroinferior
    • posteroinferior
    • posterosuperior

    This is important because vessels and nerves (specifically 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.

    Innervation

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

    Arterial Supply

    Related pathology

    See also