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March 15, 2015

Cranial Nerve 13 and Cranial Nerve 14

If you ask any medical doctor or student how many cranial nerves a human has, they all will invariably answer TWELVE. After all, that is what we all learn in medical school and that is what the answer is on any exams. However, if you are into comparative biology and anatomy esoterica, you may actually answer that animals including humans have 14 cranial nerves... not 12.

(A) illustrates human human nervous system from 1960 textbook "A Functional Approach to Neuroanatomy". (B) illustrates the nervous system of a dogfish. 
Cranial Nerve 13 (CN13)

CN13 also goes by other names including cranial nerve zero, terminal nerve, Zero Nerve, Nerve N, and NT. This nerve was first discovered in 1878 in shark brains. It was later found in humans in 1913 though its presence as a fact is still considered controversial. It is located right next to the olfactory nerve (CN1) responsible for smell. It is perhaps its very proximity to the smell nerve that CN13 may be considered (or confused as?) a part of the olfactory nerve. In mammals, this nerve is involved in sexual behavior perhaps as a way to sense pheromones? In humans CN13 is likely vestigial if one chooses to acknowledge its existence.

Cranial Nerve 7 (and 14 which is also known as nervus intermedius).
Cranial Nerve 14 (CN14)

CN14 is also known as nervus intermedius and is typically considered part of cranial nerve 7 (CN7), also known as the "facial nerve". However, given its distinctly different function as well as origin in the brain, some anatomists consider this CN14 nerve different and separate from CN7 and as such, should not be considered a part of CN7.

CN7 is responsible for facial movement.

CN14 is responsible for taste as well as sensation of the ear canal, nose, mouth. It also is responsible for salivation and tearing of the eyes.

So... now you know.

Reference:
Cranial nerves XIII and XIV: nerves in the shadows. J Multidiscip Healthc. 2013; 6: 87–91. Published online 2013 Mar 13. doi: 10.2147/JMDH.S39132
Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids. Google+ Christopher Chang, MD Bio

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