Hear This Illustration: the Right Middle Ear and the Auditory Ossicles

Hear This Illustration: The right middle ear and the auditory ossicles

The middle ear lies within the hollow temporal bone. Within this small cavity are the three auditory ossicles: the malleus, incus and stapes. The malleus, also known as the hammer, attaches to the middle of the delicate tympanic membrane or ear drum. It is the tympanic membrane that separates the middle ear from the external ear. Using an otoscope, you can usually see through the translucent tympanic membrane to see where the malleus attaches.

The vibration of the ear drum caused by sound waves is translated into mechanical movement of the ossicles. The last one in the sequence the stapes, or stirrup, places mechanical pressure on a thin membrane covering the opening, or oval window, into the cochlea. Inside the cochlea, these vibrations move fluid which, in turn, stimulate the cells of hearing inside the organ.

The middle ear communicates with the pharynx via the auditory, or Eustachian, tube. This mucosal membrane lined tube normally allows air pressure to equalize on both sides of the ear drum. Yawning, chewing, swallowing or other exaggerated movements of the mandible, stretch the tube which creates a slight “popping” sound. This is most noticeable when flying in an airplane as the cabin is pressurized while gaining altitude or descending. People with colds or inflammations of the throat region often have difficulty equalizing the pressure on eardrum because of swelling in the Eustachian tube. This can make it painful to experience pressure changes. Infants who have short Eustachian tubes are particularly prone to this discomfort so parents are advised to feed the baby during these times so that swallowing will help the tubes open and allow pressure to equalize. By the way, crying also allows expansion of the Eustachian tube. Choose your seat wisely on your next airplane trip!