Pronunciation: [pˈɛtɹəs nˈɜːv] (IPA) 
The word "petrous nerve" is spelled with the phonemes /ˈpɛtrəs nɜrv/. The first syllable, "pe", is pronounced with a short "e" sound, followed by the "t" sound. The second syllable, "trous", is pronounced with a stress on the "ou" diphthong, followed by the "s" sound. The final syllable, "nerve", is pronounced with a short "e" sound, followed by the "rv" blend. The petrous nerve is a cranial nerve located in the inner ear.
The petrous nerve refers to a sensory branch of the glossopharyngeal nerve (CN IX). It is also known as the tympanic branch or Jacobson’s nerve. The acronym "CN" stands for cranial nerve. The petrous nerve emerges from the small petrous ganglion located within the temporal bone. It plays a crucial role in carrying sensory information from the back portion of the tongue and some parts of the pharynx to the brain.
The petrous nerve's main pathway involves traveling through a canal within the temporal bone called the tympanic canaliculus. This pathway helps protect the nerve and provides it with a route from the tongue to the central nervous system. Once it exits the temporal bone, the petrous nerve joins with other branches of the glossopharyngeal nerve to form the pharyngeal plexus.
Functionally, the petrous nerve functions in the transmission of taste sensations from the posterior third of the tongue, as well as in the mediation of some sensory input from the pharynx, especially the eustachian tube. Stimulation of the petrous nerve can thus elicit sensations of taste or discomfort in the tongue, throat, or even regions surrounding the ear.
Nervus petrosus.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The term "petrous nerve" does not have a specific etymology as it is not a commonly used or recognized term in anatomy. However, I can explain the etymologies of the individual words.
The word "petrous" comes from the Latin word "petrosus", which means "rock-like" or "hard". It is derived from the Latin word "petra", meaning "rock". The term "petrous" is used in anatomy to describe structures that are dense, hard, or bony, such as the petrous part of the temporal bone in the skull.
The word "nerve" comes from the Latin word "nervus", which also means "nerve". It has its roots in the Proto-Indo-European language and is related to the Greek word "neuron", meaning "sinew" or "nerve".
