Nasal Cavity, Sinuses and Ear - LO 2
2. How do the external ear and middle ears relate to the temporomandibular joint and nasopharynx?
The external and middle ears are posterior to the TMJ and the nasopharynx.
Two openings transmit nerves between the middle ear and the region of the TMJ: the petrotympanic fissure & tympanic canaliculus. The petrotympanic fissure transmits the chorda tympani (preganglionic parasympathetics of the facial n.) from the middle ear to the infratemporal fossa. The tympanic canaliculus transmits the tympanic n. (preganglionic parasympathetics of the glossopharyngeal n.).
The middle ear communicates with the nasopharynx via the pharyngotympanic (auditory; Eustachian) tube. The pharyngotympanic tube connects from the chamber of the middle ear to the back of the nasopharynx, thus allowing equalization of pressures between these two cavities (as noted in the “popping” sensation we experience in our ears with alterations in altitude in air travel). It also allows for the drainage of materials from the middle ear. In young children (and sometimes in adults), pathogens may ascend the tube to the middle ear (and beyond) to cause otitis media (a middle ear infection). While the middle ear is an air-filled cavity, unlike the open external auditory canal, it is not in direct contact with the atmosphere outside the body.
