Cranial Nerve:

Origin, Nuclei, Passing through the Foramen and All 12 Nerves and its Functions

Cranial Nerves

Origin, Nuclei, Passing through the Foramen, All 12 Nerves and its Functions

There are 12 cranial nerve pairs. Each nerve pair serve the two sides of your brain and body. These 12 pairs of the cranial nerve of the peripheral nervous system emerge from the foramina and fissures of the skull and run across various parts of our body’s head, neck, and trunk.

The Cranial Nerves are named and numbered in Roman numerals according to their location on the brainstem and the order of their exit from the skull. All cranial nerves arise 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 originates from the brainstem.

They can be sensory or motor, or Mixed (both). Some nerves are involved in special senses, like vision, hearing, and taste, and others are involved in muscle control of the face.

Number	Mnemonic	Name	Type	Mnemonic
Cranial Nerve 1	ohh	Olfactory Nerve (CN I)	Sensory	Some
Cranial Nerve 2	ohh	Optic Nerve (CN II)	Sensory	Say
Cranial Nerve 3	ohh	Oculomotor Nerve (CN III)	Motor	Marry
Cranial Nerve 4	to	Trochlear Nerve (CN IV)	Motor	Money
Cranial Nerve 5	touch	Trigeminal Nerve (CN V)	Mixed or Both	But
Cranial Nerve 6	and	Abducens Nerve (CN VI)	Motor	My
Cranial Nerve 7	feel	Facial Nerve (CN VII)	Mixed or Both	Brother
Cranial Nerve 8	very	Vestibulocochlear Nerve (CN VIII)	Sensory	Says
Cranial Nerve 9	good	Glossopharyngeal Nerve (CN IX)	Mixed or Both	Big
Cranial Nerve 10	velvet	Vagus Nerve (CN X)	Mixed or Both	Brain
Cranial Nerve 11	such	(Spinal) Accessory Nerve (CN XI)	Motor	Matters
Cranial Nerve 12	heaven	Hypoglossal Nerve (CN XII)	Motor	More

Cranial Nerve Origin

The cranial nerve I and II arise from the cerebrum. The cranial nerve from III to XII originates from the brainstem. They emerge from a specific part of the brainstem (midbrain, pons, or medulla) or from the junction between two parts.

Midbrain - the trochlear nerve (IV) comes from the posterior side of the midbrain.
Midbrain-pontine junction - oculomotor (III)
Pons - trigeminal (V)
Pontine-medulla junction – abducens, facial, vestibulocochlear (VI-VIII)
Medulla oblongata - Posterior to the olive: glossopharyngeal, vagus, accessory (IX-XI). Anterior to the olive: hypoglossal (XII).

Cranial Nerve Nuclei

The cranial nerve nuclei are an aggregation of cells. Cranial nerves are fibers that are attached to these cell bodies. These nuclei are either sensory or motor or mixed (when they have sensory and motor functions).

The cranial nerve nuclei with motor functions can be grouped according to the following functional components to which their fibers belong:

General Somatic Efferents (GSE)
Special Visceral Efferents (SVE)
General Visceral Efferents (GVE)

The cranial nerve sensory nuclei are also grouped according to the information they receive. These functional components are:

General Somatic Afferents (GSA)
Special Somatic Afferents (SSA)
General Visceral Afferents (GVA)
Special Visceral Afferents (SVA)

Cranial Nerve Passing Through Foramen

Number	Name	Foramen
Cranial Nerve I	Olfactory	Cribriform Plate
Cranial Nerve II	Optic	Optic Canal
Cranial Nerve III	Oculomotor	Superior Orbital Fissure
Cranial Nerve IV	Trochlear	Superior Orbital Fissure
Cranial Nerve V	Trigeminal
	Ophthalmic	Superior Orbital Fissure
	Maxillary	Foramen Rotundum
	Mandibular	Foramen Ovale
Cranial Nerve VI	Abducens	Superior Orbital Fissure
Cranial Nerve VII	Facial	Internal Acoustic Meatus > Stylomastoid Foramen
Cranial Nerve VIII	Vestibulocochlear	Internal Acoustic Meatus
Cranial Nerve IX	Glossopharyngeal	Jugular Foramen
Cranial Nerve X	Vagus	Jugular Foramen
Cranial Nerve XI	Spinal Accessory	Jugular Foramen
Cranial Nerve XII	Hypoglossal	Hypoglossal Canal

Olfactory Nerve (CN I)

The Olfactory nerve is a special somatic afferent nerve that supplies the nerve to olfactory mucosa within the nasal cavity. It carries information about the smell to the brain.
It connects to the brain (not the brainstem) and passes through the cribriform plate of the skull.
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.

Optic Nerve (CN II)

The optic nerve is a particular somatic afferent nerve that supplies the nerve to the eye’s retina and brings visual information to the brain.
It connects to the brain (not the brainstem) and passes through the optic canal of the skull.
It also doesn’t have nuclei; its cell bodies are found in the retina. The optic nerve synapses with the visual relay centers of the brain.

Oculomotor Nerve (CN III)

The oculomotor nerve is both a somatic and visceral efferent motor nerve. It has two nuclei and carries two types of efferent fibers.
It is the chief motor nerve supplying the eye.
It provides fibers to the extraocular muscles and pupillary constrictor muscles. The muscles are the levator palpebrae superioris, inferior oblique, and superior, medial and inferior recti.
It connects to the midbrain and passes through the superior orbital fissure of the skull.

Trochlear Nerve (CN IV)

The Trochlear nerve is a general somatic motor nerve.
It originates from the midbrain and enters the orbit through the superior orbital fissure, supplying one extraocular muscle.
It assists in depressing and abducting the eye.
It connects to the midbrain and passes through the superior orbital fissure of the skull.

Trigeminal Nerve (CN V)

The trigeminal nerve is a mixed nerve containing both special visceral and general somatic fibers.
It 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 (click here to read more about mandibular nerve branches) exits via the foramen ovale.
All three branches of the trigeminal nerve supply sensation to the facial skin.
It has three sensory nuclei:

Mesencephalic – proprioception
Principal – light touch and discrimination
Spinal – pain, temperature, crude touch

Abducens Nerve (CN VI)

The Abducens nerve is a general somatic efferent nerve that supplies the nerve to the lateral rectus muscle (extraocular) for eye abduction.
It originates from the pontomedullary region and exits the skull via the superior orbital fissure.

Facial Nerve (CN VII)

The facial nerve 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.
It originates in the pontomedullary region, passes through the internal auditory meatus, and exits through the stylomastoid Foramen.
It enables many functions, such as facial expression, secretion of glands, and taste sensation.

Vestibulocochlear Nerve (CN VIII)

The vestibulocochlear nerve is a special somatic afferent nerve.
It comprises two parts: the vestibular nerve (which mediates balance and motion) and the cochlear nerve (which enables hearing). At the fundus of the internal acoustic meatus, both parts unite to form the vestibulocochlear nerve and enter the cranium through the internal acoustic meatus.
It originates in the pontomedullary region, passes through the internal auditory meatus, and does not leave the skull.

Glossopharyngeal Nerve (CN IX)

The glossopharyngeal nerve originates in the medulla oblongata and passes through the jugular foramen.
It draws fibers from the solitary nucleus (taste) and nucleus ambiguous (motor).
It draws more fibers from the inferior salivatory nucleus (parotid gland) and dorsal motor nucleus (DMX; pharyngeal sensation).
It enables swallowing, salivation, taste sensations, and visceral and general sensations in the oral cavity.

Vagus Nerve (CN X)

The Vagus nerve 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 a parasympathetic supply to visceral organs.
It has two ganglia, called the superior ganglion (which provides fibers for general sensory function) and the inferior ganglion (gives special sensory and visceral output), also known as nodose ganglion.
The vagus nerve controls a large number of functions, including gland secretion, peristalsis, phonation, taste, and a visceral and general sensation of the head, thorax, and abdomen.

Accessory Nerve (CN XI)

The accessory nerve is a general somatic efferent nerve.
It originates from the brainstem and spinal cord and exits the skull through the jugular foramen.
It enables 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.

Hypoglossal Nerve (CN XII)

The Hypoglossal nerve is a general somatic efferent nerve.
It originates from the brainstem and leaves the skull through the hypoglossal foramen.
Its function is to enable tongue movements.
It plays a significant role in important mouth functions such as speech and swallowing.

Function of Cranial Nerve

Olafactory Nerve

Sensory Function - Smell (olfaction)

Optic Nerve

Sensory Function - Vision

Oculomotor Nerve

Somatic Motor Function - Innervates the inferior oblique muscle and medial, inferior, and superior rectus muscles of the eye (move the eye); levator palpebrae superioris muscle (elevate eyelid)
Parasympathetic Motor Function - Innervates the sphincter pupillae muscle (constricts the pupil), and the ciliary muscle (accomodate the eye for near vision)

Trochlear Nerve

Somatic Motor Function - Innervate the superior oblique eye muscle (moves the eye inferiorly and laterally)

Trigeminal Nerve

Sensory Function - Conducts touch, temperature and pain sensation from the face, nose, mouth, nasal and oral mucosa, anterior two-thirds of tongue, and anterior scalp; part of auricle of the ear
Somatic Motor Function - Innervate the muscles of mastication, mylohyoid, digastric (anterior belly), tensor veli palatini, and tensor tympani

Abducens Nerve

Somatic Motor Function - Innervate the lateral rectus muscle of eye (abducts the eye)

Facial Nerve

Sensory Function - Taste from anterior two-thirds of tongue
Somatic Motor Function - Innervate muscles of facial expression, digastric (posterior belly), stylohyoid and stapedius muscle
Parasympathetic Motor Function - Increase secretion from the lacrimal (tear glands) and nasal mucosal glands; submandibular and sublingual salivary glands

Vestibulocochlear Nerve

Sensory Function - Hearing (cochlear branch); linear and angular acceleration, or head position in space/equilibrium (vestibular branch)

Glossopharyngeal Nerve

Sensory Function - Touch and taste from the posterior 1/3 of the tongue; visceral sensory from the carotid sinus and bodies.
Somatic Motor Function - Innervate the pharyngeal muscle Stylopharyngeus.
Parasympathetic Motor Function - Increase secretion from the parotid salivary gland.

Vagus Nerve

Sensory Function - Visceral sensation (excluding pain) from heart, lungs, abdominal organs, bronchi, trachea, larynx, pharynx, gastrointestinal tract to level of descending colon. General sensation from the external acoustic meatus, eardrum, and pharynx.
Somatic Motor Function - Innervates pharyngeal and laryngeal muscles and muscles at base of tongue.
Parasympathetic Motor Function - Innervates smooth muscles and glands of the heart, lungs larynx, trachea, and most abdominal organs.

Accessory Nerve

Somatic Motor Function - Innervates the trapezius and sternocleidomastoid muscle.

Hypoglossal Nerve

Somatic Motor Function - Innervates intrinsic and extrinsic tongue muscles

References

1. Human Anatomy By B D Chaurasia's 7th Edition

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