Ear

Question 1

What is sensory innervation of the middle ear?

Answer 1

There is a sensory nerve plexus sitting on the promontory and that is glossopharyngeal nerve (IX).

This is because the middle ear is an outpocketing of the pharynx so mucosa is also glossopharyngeal.

Question 2

Describe the path of the facial nerve.

Answer 2

The facial nerve enters the internal auditory meatus.

From there it passes the inner ear to reach the genu/geniculate ganglion which contains the cell bodies of general sensation and special sensory.

At the genu it gives off the greater petrosal nerve which carries special sensory nerves from the palate and preganglionic parasympathetics for the pterygopalatine ganglion.

It gives off a branch carrying motor neurons to the stapedius

After that the chorda tympani comes off which carries special sensory from the anterior 2/3 of the tongue and the preganglionic parasympathetics for the submandibular gland (crosses the petrotympanic fissure and it joins the ligual nerve)

The facial nerve than exits through the stylomastoid foramen giving off a branch called the posterior auricular nerve.

Then it crosses the parotid gland and innervates the muscles of facial expression and posterior digastric + stylohyoid.