QS Study

The tympanic membrane is a thin, translucent partition between the external car and the middle car. It acts to transmit sound waves from the air in the external auditory canal to the ossicles of the middle ear.

Features –

It is oval, measuring about 9 x 10 mm. It is placed obliquely at an angle of 40-45° with the floor of the meatus. It faces downwards, forwards and laterally. It has outer and inner surfaces. It also serves as the lateral wall of the tympanic cavity, separating it from the external auditory canal.

The outer surface is lined by thin skin. The inner surface provides attachment to the handle of malleus. It is convex. The point of maximum convexity lies at the tip of the handle of the malleus, called umbo. It is formed of a layer of skin on the outside and a layer of mucous membrane on the inside, lying back-to-back on a layer of supporting fibers.

Parts:

  1. Pars tensa
  2. Pars flaccid.

Tympanic Membrane 1

Fig: Tympanic Membrane

Blood Supply –

  1. The inner surface is supplied by the tympanic branch of the maxillary artery and the posterior auricular artery.
  2. The outer surface by-deep auricular branch of the maxillary. Veins from the outer surface drain into an external jugular vein. The inner surface drains into the transverse sinus and the venous plexus around an auditory tube.

Lymphatic drainage – To preauricular and retropharyngeal lymph nodes.

Nerve Supply –

(1) Outer surface: The anteroinferior part is supplied by the auriculotemporal nerve and the posterosuperior part by the auricular branch of the vagus nerve.

(2) Inner surface: It is supplied by the tympanic branch of the glossopharyngeal nerve.

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