12 cranial nerves
Author:
Jana Vasković MD·Reviewer: Nicola McLaren MSc
Last reviewed: March 03, 2022
Reading time: 23 minutes
Facial nerve (lateral right view)
You know when someone mentions cranial nerves and you roll your
eyes all the way back to your
midbrain? We know that cranial nerves have always been a challenging subject among anatomy students. So we’re here to make it easier for you.
Cranial nerves anatomy is essential for almost any medical specialty since they control so many body functions, such as rolling your
eyes when you’re annoyed by something. So let’s break the stigma of them being hard to understand, and learn this important
neuroanatomy topic once and for all.
Key facts about the cranial nerves
Table quiz
Definition A set of 12 peripheral nerves emerging from the brain that innervate the structures of the head, neck, thorax and abdomen.
Nerves Olfactory nerve (CN I), optic nerve (CN II), oculomotor nerve (CN III), trochlear nerve (CN IV), trigeminal nerve (CN V), abducens nerve (CN VI), facial nerve (CN VII), vestibulocochlear nerve (CN VIII), glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), and hypoglossal nerve (CN XII).
Mnemonics:
- Oh, Oh, Oh, To Touch And Feel Very Good Velvet, such-A Heaven
- On, On, On, They Traveled And Found Voldemort Guarding Very Ancient Horcruxes.
Types of nerves - Sensory: Olfactory nerve (CN I), optic nerve (CN II), vestibulocochlear nerve (CN VIII)
- Motor: Oculomotor nerve (CN III), trochlear nerve (CN IV), abducens nerve (CN VI), accessory nerve (CN XI), hypoglossal nerve (CN XII).
- Mixed (both): trigeminal nerve (CN V), facial nerve (CN VII), glossopharyngeal nerve (CN IX), vagus nerve (CN X).
Mnemonic (by the numerical order): Some Say Money Matters, But My Brother Says Big Brains Matter Most
Contents
Anatomy
12 cranial nerves list
Mnemonics
Olfactory nerve (CN I)
Optic nerve (CN II)
Oculomotor nerve (CN III)
Trochlear nerve (CN IV)
Trigeminal nerve (CN V)
Abducens nerve (CN VI)
Facial nerve (CN VII)
Vestibulocochlear nerve (CN VIII)
Glossopharyngeal nerve (CN IX)
Vagus nerve (CN X)
Accessory nerve (CN XI)
Hypoglossal nerve (CN XII)
Sources
+ Show all
Recommended video: Cranial nerves
Overview of the 12 cranial nerves.
Anatomy
Cranial nerves are the 12 nerves of the
peripheral nervous system that emerge from the
foramina and fissures of the
cranium. Their numerical order (1-12) is determined by their
skull exit location (rostral to caudal). All cranial nerves originate from
nuclei in the
brain. Two originate from the forebrain (Olfactory and Optic), one has a nucleus in the
spinal cord (Accessory) while the remainder originate from the
brainstem.
There's a LOT to learn about the cranial nerves. You might like to
ease yourself into this topic with our cranial nerves quizzes and labeling exercises.Cranial nerves supply sensory and motor information to structures of the
head and neck, controlling the activity of this region. Only the vagus nerve extends beyond the neck, to innervate
thoracic and
abdominal viscera.
12 cranial nerves (diagram)
We’re sure that while reading textbooks, you encountered with
terms such as afferent, efferent, mixed, general, visceral, special, somatic etc, these refer to modalities of the cranial nerves. They often bring confusion, so let’s explain them before proceeding.
The function of a
nerve is to carry sensory and/or motor information between the body and the
brain. If the information goes from the brain to the periphery, then it is an
efferent (motor) nerve. If it travels from the periphery to the brain, then it is an
afferent (sensory) nerve. Nerves that do both are
mixed nerves. Unlike
spinal nerves which are always mixed, cranial nerves can be purely motor, purely sensory or mixed.
Now let’s understand the terms special, general, somatic and visceral. The information is classified as special if it travels from our special senses (vision, smell,
taste, hearing and balance), while general describes information to/from everywhere else. The information carried by a nerve is called somatic if it goes to/from the
skin and
skeletal muscles, or visceral if it travels to/from our
internal organs.
Combining these categories allows us to define the functional components of a nerve. For example, if the nerve fibers exclusively carry special sensory information, it is called a special afferent nerve. If it carries other types of sensory information, like touch, pressure, pain, temperature, then it is a general afferent nerve.
If the nerve carries information to
smooth muscle,
cardiac muscle or
glands, then it is a visceral efferent nerve. If it carries information to skin or skeletal muscle, then it is a somatic efferent nerve. As the term visceral is often a synonym for
autonomic (nervous system), note that general visceral nerves carry autonomic nerve fibers to/from the target organs. The exception to this are the special visceral efferent nerves, sometime described as branchial efferent (BE). These are motor nerves, named for the embryological origin of the fibres. Information of movement and position (proprioception) from somatic structures like muscles, tendons, and
joints is carried by general somatic afferent nerves. Lastly, be aware that there is no special somatic efferent classification.
So to conclude, considering the possible directions and modalities, cranial nerves can be:
General somatic afferent (GSA)
General somatic efferent (GSE)
General visceral afferent (GVA)
General visceral efferent (GVE)
Special somatic afferent (SSA)
Special visceral afferent (SVA)
Special visceral efferent (SVE)
Here is a cranial nerves starter pack for you:
12 cranial nerves Explore study unit Cranial nerve nuclei Explore study unit 12 cranial nerves list
To get familiar with these nerves, let’s list all them in one place.
Cranial nerves list
Table quiz
Cranial nerve 1 Olfactory nerve (CN I) - sensory
Cranial nerve 2 Optic nerve (CN II) - sensory
Cranial nerve 3 Oculomotor nerve (CN III) - motor
Cranial nerve 4 Trochlear nerve (CN IV) - motor
Cranial nerve 5 Trigeminal nerve (CN V) - mixed
Cranial nerve 6 Abducens nerve (CN VI) - motor
Cranial nerve 7 Facial nerve (CN VII) - mixed
Cranial nerve 8 Vestibulocochlear nerve (CN VIII) - sensory
Cranial nerve 9 Glossopharyngeal nerve (CN IX) - mixed
Cranial nerve 10 Vagus nerve (CN X) - mixed
Cranial nerve 11 (Spinal) Accessory nerve (CN XI) - motor
Cranial nerve 12 Hypoglossal nerve (CN XII) - motor
Test your knowledge about the cranial nerves by taking this quiz which is specially designed to cover the most important anatomy facts about the 12 cranial nerves!
Overview of the 12 cranial nerves (12 structures).
Start quiz
48
Basic structure identification questions
12
Advanced structure identification questions
60
Exam questions (Question bank)
Mnemonics
If we take the first letter of each nerve, we can build a mnemonic to help remember the cranial nerve names!
Oh, Oh, Oh, To Touch And Feel Very Good Velvet, Such A Heaven
Olfactory nerve (CN I)
Optic nerve (CN II)
Occulomotor nerve (CN III)
Trochlear nerve (CN IV)
Trigeminal nerve (CN V)
Abducens nerve (CN VI)
Facial nerve (CN VII)
Vestibulocochlear nerve (CN VIII)
Glossopharyngeal nerve (CN IX)
Vagus nerve (CN X)
Accessory nerve (CN XI)
Hypoglossal nerve (CN XII)
Or, if you’re a member of the Harry Potter fandom, you can learn this one: On, On, On, They Traveled And Found Voldemort Guarding Very Ancient Horcruxes. Remember these, and you’ll always be able to recall the cranial nerves in their numerical order.
Recommended video: Cranial nerves mnemonic
Memorize the names and functions of the cranial nerves here!
In addition, to remember if a nerve is sensory, motor or both in numerical order, remember this:
"Some say money matters, but my brother says big brains matter most"
Sensory (CN I)
Sensory (CN II)
Motor (CN III)
Motor (CN IV)
Both (CN V)
Motor (CN VI)
Both (CN VII)
Sensory (CN VIII)
Both (CN IX)
Both (CN X)
Motor (CN XI)
Motor (CN XII)
Now that we’ve learned the tricks on how to remember cranial nerves and their modalities, let’s get introduced to the anatomy of each one of them.
Olfactory nerve (CN I)
Cranial nerve 1 is a special somatic afferent nerve which innervates the olfactory mucosa within the
nasal cavity. It carries information about smell to the brain.
Key facts about the olfactory nerve (CN I)
Table quiz
Type SVA/SSA*
Nucleus None
Field of innervation Sensory: Nasal mucosa
The many branches of the
olfactory nerve, called fila olfactoria, pass from the nasal cavity through the cribriform plate of the
ethmoid bone. They terminate in the olfactory bulb, which continues as the olfactory tract. Within the brain, the fibers of the olfactory tract disperse and end within the olfactory cortex (piriform cortex,
amygdala, entorhinal cortex).
The olfactory nerve doesn’t have a specific nucleus of its own. Instead its cell bodies are found in the olfactory area-the nasal mucosa that covers the roof of the nasal cavity.
*Note that there is an ongoing discussion about the modality of the olfactory nerve. Some authors say it’s SSA, whilst the others classify it as SVA. In any case, you won't make a mistake if you simply say that it is a special afferent nerve.
Find out more about the olfactory nerve in the study unit below, or take the quiz to see what you've learned so far!
Olfactory nerve (CN I) Explore study unit Custom quiz: Olfactory nerve Start quiz Optic nerve (CN II)
Cranial nerve 2 is a special somatic afferent nerve which innervates the retina of the eye and brings visual information to the brain.
Key facts about the optic nerve (CN II)
Table quiz
Type SSA
Nucleus None
Field of innervation Sensory: Retina
Neural fibers originate from the photoreceptors of the retina. They converge at the optic disc, forming the
optic nerve. The optic nerve leaves the
orbit through the optic canal.
On the floor of the middle cranial fossa, the nasal parts of each nerve cross to the opposite side forming the optic chiasm. The nerve fibers then continue as the two optic pathways. CN II also doesn’t have its own nuclei, but instead its cell bodies are found in the retina. The optic nerve synapses with the visual relay centers of the brain.
Eager to learn everything about the optic nerve? Check out this study unit and quiz we have prepared for you.
Optic nerve (CN II) Explore study unit Custom quiz: Optic nerve Start quiz Oculomotor nerve (CN III)
Cranial nerve 3 is both a somatic and visceral efferent motor nerve. This means it has two nuclei and carries two types of efferent fibers. As the name suggests, the
oculomotor nerve is the chief motor nerve supplying the eye.
It originates from the midbrain and leaves the skull through the superior orbital fissure to enter the orbit where it enables eye movement, constriction of the pupil (miosis) and
lensaccommodation.
Key facts about the oculomotor nerve (CN III)
Table quiz
Type GSE, GVE (parasympathetic)
Nuclei Nucleus of oculomotor nerve (GSE)
Accessory nuclei of oculomotor nerve (Edinger-Westphal) (GVE)
Field of innervation Motor: all extraocular muscles except for the lateral rectus and superior oblique (GSE);
ciliary muscle,
sphincter pupillae muscle (GVE)
Solidify your knowledge about the oculomotor nerve with this study unit:
Oculomotor, trochlear and abducens nerves (CN III, IV & VI) Explore study unit Trochlear nerve (CN IV)
Cranial nerve 4 is a general somatic motor nerve. The
trochlear nerve originates from the midbrain and enters the orbit through the superior orbital fissure, supplying one extraocular muscle thus playing a role in eye movement.
Key facts about the trochlear nerve (CN IV)
Table quiz
Type GSE
Nuclei Nucleus of trochlear nerve
Field of innervation Motor: Superior oblique muscle
We have you covered with the anatomy of the trochlear nerve in the study unit below.
Oculomotor, trochlear and abducens nerves (CN III, IV & VI) Explore study unit Trigeminal nerve (CN V)
Cranial nerve 5 is a mixed nerve, containing both special visceral and general somatic fibers. The fibers originate from the
brainstem, forming the trigeminal ganglion near the apex of the petrous part of the
temporal bone.
The
trigeminal nerve divides into three divisions;
ophthalmic nerve (CN V1),
maxillary nerve (CN V2) and
mandibular nerve (CN V3). Each of them leaves the skull through a different opening. Ophthalmic leaves through the superior orbital fissure, maxillary through the
foramen rotundum and the mandibular nerve exits via the foramen ovale.
Key facts about the trigeminal nerve (CN V)
Table quiz
Type SVE, GSA
Nuclei Motor nucleus of trigeminal nerve (SVE)
Principal sensory nucleus of trigeminal nerve (GSA)
Spinal nucleus of trigeminal nerve (GSA)
Mesencephalic nucleus of trigeminal nerve (GSA)
Divisions Ophthalmic nerve (CN V1)
Maxillary nerve (CN V2)
Mandibular nerve (CN V3)
Field of innervation Motor: Muscles of mastication,
mylohyoid, anterior belly of
digastric,
tensor tympani muscles (SVE)
Sensory: Scalp, face, orbit, paranasal sinuses, anterior two-thirds of the tongue (GSA)
All three branches of the trigeminal nerve supply sensation to the facial skin. The areas of cutaneous innervation (
dermatomes) are as follows; Ophthalmic nerve (CN V1 dermatome) supplies the forehead, orbit and nose, maxillary nerve (CN V2 dermatome) the zygomatic region and upper lip, while the mandibular nerve (CN V3 dermatome) innervates the buccal skin, lower lip and skin of the mandibular region.
To learn everything about the trigeminal nerve and its divisions, we recommend you go through the following study materials and custom quiz:
Ophthalmic nerve (CN V1) Explore study unit Maxillary nerve (CN V2) Explore study unit Mandibular nerve (CN V3) Explore study unit Custom quiz: Trigeminal nerve Start quiz Abducens nerve (CN VI)
Cranial nerve 6 is a general somatic efferent nerve which innervates the
lateral rectus muscle (extraocular). The
abducens nerve originates from the brainstem and exits the skull via the superior orbital fissure.
Key facts about the abducens nerve (CN VI)
Table quiz
Type GSE
Nucleus Nucleus of abducens nerve
Field of innervation Motor: Lateral rectus muscle
Although it may seem the least relevant, the abducens nerve plays a very important role in eye movement. Just ask anyone with strabismus.
Learn all about this nerve in the study unit below and then test what you've learned so far about the oculomotor, trochlear and abducens nerve with our qustom quiz below!
Oculomotor, trochlear and abducens nerves (CN III, IV & VI) Explore study unit Custom quiz: Oculomotor, trochlear and abducens nerves Start quiz Facial nerve (CN VII)
Cranial nerve 7 is a multimodal nerve, carrying both general and special fibers. It originates from the brainstem as two separate divisions; a larger primary root carrying motor fibers and a smaller intermediate nerve carrying sensory and parasympathetic fibers.
The two divisions leave the cranial cavity through the internal acoustic meatus and then travel through the facial canal. Here they join forming the
facial nerve proper and leave the cranium together through the stylomastoid foramen. Once the facial nerve reaches the face it enables many functions, such as facial expression, secretion of glands and taste sensation.
Key facts about the facial nerve (CN VII)
Table quiz
Type GVE (parasympathetic), SVE, GVA, SVA, GSA
Nuclei Superior salivatory nucleus (GVE)
Motor nucleus of facial nerve (SVE)
Nuclei of solitary tract (GVA, SVA)
Spinal nucleus of trigeminal nerve (GSA)
Field of innervation Sensory: middle ear, nasal cavity, soft palate (GVA); anterior two-thirds of the tongue (SVA); external auditory meatus (GSA)
Motor: lacrimal, submandibular, sublingual, basal, palatine glands (GVE); muscles of facial expression (SVE)
Even though it may seem like a never ending story, the facial nerve isn’t so hard to learn if you have a good approach.
We offer you one with our study unit and custom quiz:
Facial nerve (CN VII) Explore study unit Custom quiz: Facial nerve Start quiz Vestibulocochlear nerve (CN VIII)
Cranial nerve 8 is a special somatic afferent nerve. It is comprised of two parts: the vestibular nerve and the cochlear nerve. The
cochlear component enables hearing, while the vestibular part mediates balance and motion. At the fundus of internal acoustic meatus, both parts unite to form the
vestibulocochlear nerve and enter the cranium through the internal acoustic meatus.
Key facts about the vestibulocochlear nerve (CN VIII)
Table quiz
Type SSA
Nuclei Vestibular nuclei
Dorsal and ventral cochlear nuclei
Field of innervation Sensory: Spiral organ (of Corti), macula of utricle, macula of saccule, ampullae of the semicircular canals (SSA)
The two components synapse with their respective nuclei in the brainstem. To save you from confusion, note that dorsal and ventral cochlear nuclei terminology varies. Sometimes you’ll see them as anterior and posterior cochlear nuclei, and elsewhere simply grouped as the auditory nuclei.
Master the vestibulocochlear nerve anatomy with our user resources:
Vestibulocochlear nerve (CN VIII) Explore study unit Custom quiz: Vestibulocochlear nerve Start quiz Glossopharyngeal nerve (CN IX)
Cranial nerve 9 is another multimodal nerve. It originates from the brainstem and leaves the skull through the jugular foramen. It enables
swallowing, salivation, and taste sensation, as well as visceral and general sensation in the
oral cavity.
Key facts about the glossopharyngeal nerve (CN IX)
Table quiz
Type SVE, GVE (parasympathetic), SVA, GVA, GSA
Nuclei Nucleus ambiguus (SVE, GVA)
Inferior salivatory nucleus (GVE)
Nuclei of solitary tract (SVA, GVA)
Spinal nucleus of trigeminal nerve (GSA)
Field of innervation Motor:
stylopharyngeus and pharyngeal constrictors (SVE); parotid gland (GVE)
Sensory: posterior one-third of the tongue (SVA); middle ear,
pharynx, epiglottis, carotid body, carotid sinus (GVA); posterior one-third of the tongue, soft palate (GSA)
Fortify your knowledge about the
glossopharyngeal nerve with these Kenhub resources.
Glossopharyngeal nerve (CN IX) Explore study unit Custom quiz: Glossopharyngeal nerve Start quiz Vagus nerve (CN X)
Cranial nerve 10 is also a multimodal nerve, It originates from multiple nuclei in the brainstem, and exits the skull through the jugular foramen. It is the longest cranial nerve and the only one to leave the
head and neck region. The
vagus nerve travels into the thoracic and abdominal cavities, providing parasympathetic supply to visceral organs.
Key facts about the vagus nerve (CN X)
Table quiz
Type GVE (parasympathetic), SVE, SVA, GVA, GSA
Nuclei Posterior nucleus of vagus nerve (dorsal motor nucleus) (GVE)
Nucleus ambiguus (SVE)
Nuclei of solitary tract (SVA, GVA)
Spinal nucleus of trigeminal nerve (GSA)
Field of innervation Motor: thoracic and abdominal viscera (GVE); laryngeal and pharyngeal muscles (SVE)
Sensory: epiglottis (SVA); thoracic and abdominal viscera, carotid body (GVA); external acoustic meatus, retroauricular skin, posterior part of
meninges (GSA)
CN 10 has two ganglia, called the superior ganglion of the vagus nerve and the inferior ganglion of the vagus nerve (nodose ganglion). The former provides fibers for general sensory function, while the latter gives special sensory and visceral output.
The vagus nerve controls a large number of functions, including gland secretion, peristalsis, phonation, taste, visceral and general sensation of the head,
thorax and
abdomen. This cranial nerve is frequently tested in anatomy exams.
Use our content to swot up on the vagus nerve and ace your cranial nerve exams!
Vagus nerve (CN X) Explore study unit Custom quiz: Vagus nerve Start quiz Accessory nerve (CN XI)
Cranial nerve 11 is an efferent nerve originating from the brainstem and spinal cord. It exits the skull through the jugular foramen, acting to enable phonation and movements of the head and
shoulders.
Sensory fibers of the
cervical plexus join the accessory nerve enabling general sensation for its target muscles. So when you feel comfortable while getting a shoulder massage, thank your cervical plexus for that.
Key facts about the accessory nerve (CN XI)
Table quiz
Type GSE/SVE*
Nuclei Ambiguus
Nucleus of the accessory nerve (C1-C5)
Field of innervation Motor: Laryngeal muscles, sternocleidomastoid, trapezius
The (spinal) accessory nerve is interesting in that anatomists still don’t agree on exactly where its nerve fibers originate from. *Some debate that it is a SVE nerve, believing the spinal accessory nucleus to be continuous with the nucleus ambiguus (which is SVE). Yet others describe it as a GSE nerve, providing motor innervation to the three muscles without nucleus ambiguus involvement. There are also anatomists who believe that the CN XI contains both SVE and GSE nerves, receiving fibers from both nuclei sources.
Learn everything about the
accessory nerve with our Kenhub study materials.
Accessory nerve (CN XI) Explore study unit Custom quiz: Accessory nerve Start quiz Hypoglossal nerve (CN XII)
Cranial nerve 12 is a general somatic efferent nerve originating from the brainstem. It leaves the skull through the hypoglossal foramen. It’s function is to enable
tongue movements.
Key facts about the hypoglossal nerve (CN XII)
Table quiz
Type GSE
Nucleus Nucleus of hypoglossal nerve
Field of innervation Motor: Intrinsic tongue muscles, extrinsic tongue muscles (except for the palatoglossus)
The hypoglossal nerve is extremely important for smooth daily functioning of every person, as it plays a significant role in important mouth functions such as speech and swallowing. Similar to CN XI, the hypoglossal nerve also interacts with the cervical plexus. It receives GSE fibers from C1 and C2 spinal nerves, and GSA fibers from the spinal ganglion of C2 spinal nerve.
Master the
hypoglossal nerve anatomy with our study material:
Hypoglossal nerve (CN XII) Explore study unit Custom quiz: Hypoglossal nerve Start quiz Sources
All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our
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References:
Blumenfeld, H. (2018). Neuroanatomy through clinical cases (2nd ed.). Sunderland, MA: Sinauer.
Haines, D. E. (2012). Neuroanatomy: an atlas of structures, sections, and systems (8th ed.). Philadelphia, PA: Wolters Kluwer/ Lippincott Williams & Wilkins Health.
Jacobson, S., & Marcus, E. M. (2008). Neuroanatomy for the neuroscientist. New York: Springer.
Kahle, W., Frotscher, M., & Spitzer, G. (2003). Nervous system and sensory organs. New York: Thieme.
Waxman, S. G. (2010). Clinical neuroanatomy (26th ed.). New York: McGraw-Hill Medical.
Illustrations:
Facial nerve (lateral right view) - Paul Kim
Cranial nerves (diagram) - Paul Kim
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