The middle ear
'Γhe middle ear (Fig. 5.19) consists of:
The tympanic cavity, which lies within the tympanic bulla of the petrous Iempcjral bone of the skull. It is lined w ith ciliated columnar mucous membrane and is filled with air.
In the dorsal part of the cavity are the auditory ossicles. Opening into the cavity is the Iuistcic Iiicin or auditory tube. This is a short canal which connects the nasopharynx to the middle car and whose function is to equalise air pressure on either side of the tympanic membrane.The tympanic membrane or ear drum forms the boundary between the external and middle ears at the end of the external auditory meatus. It is a thin semi-transparent oval membrane w hose function is to convey the vibrations caused by sound waves from the external auditory meatus to the auditory ossicles.
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The (Iiiditorif ossicles arc three small bones forming a Ilexiblechain w hich connect the tympanic membrane to the oval window of the inner ear. The bones arc linked by synovial joints and are known as:
- Mnlkiis. or hammer
- Incus. or anvil
- Stupes, orstirrup.
The function of the ossicles is to transmit the vibrations caused bv sound waves across the W
middle ear to the inner car.
Fig. 5.19 Section through the can∙ne or ie∣∣∏e ear