Cranial nerves

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CRANIAL NERVES

CRANIAL NERVES - Bottom ViewCranial nerves are those that make connection with the brain. The 12 pairs of cranial nerves are given a specific nomenclature and are numbered in Roman numerals according to their apparent origin in the rostrocaudal sense.
They are linked with the cortex of the brain by the corticonuclear fibers that originate from the neurons of the motor areas of the cortex, descending mainly in the genicular part of the inner capsule to the brainstem.
Sensory or afferent cranial nerves originate from neurons located outside the brain, grouped to form ganglia, or located in peripheral sense organs.

The nuclei that give rise to ten of the twelve pairs of cranial nerves lie in vertical columns in the brainstem and correspond to the gray matter of the spinal cord.

According to Component Works1, the cranial nerves can be classified into Motors, Sensitive and Mixed.

The Motors (pure) they are the ones that move the eye, the tongue and the accessory posterior muscles of the neck.

Are they:

III & #8211; Oculomotor Nerve

IR & #8211; Trochlear Nerve

VI & #8211; Abducent Nerve

XI & #8211; Accessory Nerve

XII & #8211; Hypoglossal Nerve

The Sensitives (pure) They are intended for the sense organs and are therefore called sensory rather than sensory, which do not refer to general sensitivity (pain, temperature and touch).

The sensory ones are:

I & #8211; Olfactory nerve

II & #8211; Optical Nerve

VIII & #8211; Vestibulocochlear Nerve

The Mixed (motors and sensitives) are four in number:

V & #8211; Triplet

VII & #8211; Facial nerve

IX & #8211; Glossopharyngeal Nerve

X & #8211; Vacant Nerve

Five of them still have vegetative fibers, constituting the peripheral chronic part of the autonomous system.

They are as follows:

III & #8211; Oculomotor Nerve

VII & #8211; Facial nerve

IX & #8211; Glossopharyngeal Nerve

X & #8211; Vacant Nerve

XI & #8211; Accessory Nerve

CRANIAL NERVE SUMMARY
CRANIAL NERVES

 

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

The craniocaudal sequence of the cranial nerves is as follows:

I
II
III
IV
V
SAW
  Olfactory
Optical
Oculomotor
Trochlear
Triplet
Abducent
  VII
VIII
IX
X
XI
XII
  Facial
Vestibulocochlear
Glossopharyngeal
Vague
Accessory
Halibut

I. Olfactory Nerve

The olfactory nerve fibers are distributed over a special area of the nasal mucosa that is called the olfactory mucosa. Because of the large amount of individualized fascicles that traverse the ethmoidal sieve separately, it is commonly referred to as the olfactory nerves, not simply the olfactory nerve (right and left).

It is an exclusively sensitive nerve whose fibers conduct olfactory impulses and are classified as special visceral afferents. More information about the olfactory nerve can be found in Telencephalon (Rhinocephalus).

NERVE OLFATORY
Olfactory nerve

 

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
NERVE OLFATORY
 
Olfactory nerve
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location   Passage
Olfactory Nerve - Location Olfactory Nerve - Passage

II. Optical Nerve

It consists of a thick bundle of nerve fibers that originate in the retina, emerge near the posterior pole of each eye bulb, and penetrate the skull through the optic canal. Each optic nerve joins with the opposite nerve, forming the optic chiasm, where there is partial crossing of its fibers, which continue in the optic tract to the lateral geniculate body. The optic nerve is an exclusively sensitive nerve, whose fibers conduct visual impulses and are classified as special somatic afferents.

OPTIC NERVE
 
Optical Nerve
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location   Passage
Optical Nerve - Location Optical Nerve - Passage

III. Oculomotor Nerve

IV. Trochlear Nerve

SAW. Abducent Nerve

These are motor nerves that penetrate the orbit through the superior orbital fissure and are distributed to the extrinsic muscles of the ocular bulb, as follows: upper eyelid elevator, superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, inferior oblique. All these muscles are innervated by the oculomotor, except for the lateral rectus and superior oblique, innervated by the abducens and trochlear nerves, respectively. The fibers that innervate the extrinsic muscles of the eye are classified as somatic efferents.

The oculomotor nerve is born in the medial sulcus of the cerebral peduncle; the trochlear nerve just below the inferior colliculus; and the abducent nerve in the inferior pontine sulcus near the midline.

The three nerves in question approach, still inside the skull, to cross the superior orbital fissure and reach the orbital cavity, distributing it to the extrinsic muscles of the eye.

The oculomotor nerve also conducts vegetative fibers, which go to the intrinsic musculature of the eye, which moves the iris and lens.

OCULOMOTOR, TROCLEAR AND ABDUCENT NERVE
 
OCULOMOTOR, TROCLEAR AND ABDUCENT NERVE
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location
Oculomotor Nerve
  Passage
Oculomotor Nerve
Oculomotor Nerve - Location Oculomotor Nerve - Passage
 

Location
Trochlear Nerve

   

Passage
Trochlear Nerve

Troclear Nerve - Location Trochlear Nerve - Passage
 

Location
Abducent Nerve

   

Passage
Abducent Nerve

Abducente Nerve - Location Abducent Nerve - Passage

V. Trigeminal Nerve

The trigeminal nerve is a mixed nerve and the sensory component is considerably larger. It has a sensitive root and a motor. The sensory root is formed by the central extensions of the sensory neurons, located in the trigeminal ganglion, which is located in the trigeminal cavus, over the petrous part of the temporal bone.

Peripheral extensions of the trigeminal ganglion sensory neurons form, distally to the ganglion, the three branches of the trigeminal nerve: ophthalmic nerve, maxillary nerve and mandibular nerve, responsible for the general somatic sensitivity of most of the head, through fibers that are classified as afferent. somatic general.

The motor root of the trigeminal consists of fibers that accompany the mandibular nerve, distributed to the masticatory muscles. The most frequently observed medical problem in relation to the triplet is neuralgia, which is manifested by very intense painful crises in the territory of one branch of the nerve.

Trigemius Nerve - Ophthalmic and Maxillary Branch

1. Ophthalmic NerveIt crosses the superior orbital fissure (along with the III, IV, VI cranial pairs and the ophthalmic vein) and upon reaching the orbit provides three terminal branches, which are the nasociliary, frontal and lacrimal nerves.

The ophthalmic nerve is responsible for the sensitivity of the orbital cavity and its contents, while the optic nerve is sensory (vision).

2. Maxillary Nerve: is the second branch of the trigeminal nerve. It crosses the pterygopalatine fossa as if it were an airway to enter the inferior orbital fissure and penetrate the orbital cavity, at which point it is called infraorbital nerve.

The infraorbital nerve continues in the same forward direction, passing through the floor of the orbit, successively passing through the infraorbital groove, canal and foramen, and through the latter externalizes to innervate the soft tissues located between the lower eyelid (n. Lower eyelid). , nose (n.nasal) and upper lip (n. upper lip).

The infraorbital nerve (terminal branch of the maxillary nerve) provides as collateral branches the medial superior alveolar nerve and the anterior superior alveolar nerve, which run downwards.

In the vicinity of the apexes of the roots of the upper teeth, the three upper alveolar nerves emit branches that are abundantly anastomosed to form the upper dental plexus.

3. Mandibular Nerve: is the third branch of the trigeminal nerve. It crosses the skull through the foramen ovale and just below it branches into a true bouquet, the two main branches being the lingual and inferior alveolar nerve.

The lingual nerve goes to the tongue, giving general sensitivity to its anterior two thirds.

The inferior alveolar nerve enters the mandible foramen and runs through the bone through the mandible canal to the central incisor tooth.

At about the time of the second premolar, the inferior alveolar nerve emits a collateral branch, which is the mental nerve (mental nerve), which emerges from the foramen of the same name to provide general sensitivity to the soft parts of the chin.

Within the mandible canal, the inferior alveolar nerve branches, but its branches anastomously clump to form the lower dental plexus, from which the lower dental branches to the lower teeth depart.

The motor part of the mandibular nerve innervates the masticatory muscles (temporal, masseter, and medial and lateral pterygoid), with nerves having the same name as the muscles.

TRENKEY NERVE & #8211; Ophthalmic and Maxillary RAMS
 
Trigemius Nerve - Ophthalmic and Maxillary Branch
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
TRENKEY NERVE & #8211; Jawbone
 
Trigemius Nerve - Mandibular Branch
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location   Passage
Trigemius Nerve - Mandibular Branch - Location Trigemius Nerve - Mandibular Branch - Passage

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VII. Facial nerve

It is also a mixed nerve, with a motor root and a taste sensory root. It emerges from the bulbous pontine sulcus through a motor root, the facial nerve itself, and a sensitive and visceral root, the intermediate nerve. Together with the vestibulo-cochlear nerve, the two components of the facial nerve penetrate the internal acoustic meatus, within which the intermediate nerve loses its individuality, forming a single nerve trunk that penetrates the facial canal.

The motor root is represented by the facial nerve itself, while the sensory root is called the intermediate nerve.

Both have apparent origin in the inferior pontine sulcus and run parallel to the internal acoustic meatus where they penetrate along with the vestibulocochlear nerve.

Within the internal acoustic meatus, the two nerves (facial and intermediate) penetrate a proper canal dug into the petrous part of the temporal bone, which is the facial canal.

The motor fibers cross the parotid gland reaching the face, where they give two initial branches: the facial and the cervical facial, which fan out to innervate all the cutaneous muscles of the head and neck.

Some motor fibers go to the hyoid-style muscle and the posterior belly of the digastric.

The sensory (gustatory) fibers follow a branch of the facial nerve that is the tympanic cord, which will join the lingual nerve (mandibular branch, third branch of the trigeminal), taking as a vector to distribute in the anterior two thirds of the language.

The facial nerve also has vegetative (parasympathetic) fibers that utilize the intermediate nerve and then follow the greater petrous nerve or tympanic cord (both branches of the facial nerve) to innervate the lacrimal, nasal, and salivary glands (sublingual and submandibular glands). .

In summary, the facial nerve gives motor innervation to all cutaneous muscles of the head and neck (hyoid-style muscle and posterior digastric belly).

FACIAL NERVE
 Facial nerve
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location Passage
Facial Nerve - Location   Facial Nerve - Passage

VIII. Vestibulocochlear Nerve

Consisting of two groups of perfectly individualized fibers that form, respectively, the vestibular and cochlear nerves. It is an exclusively sensitive nerve, which penetrates the bridge in the lateral portion of the bulbous-pontine sulcus, between the emergence of the VII pair and the cerebellum floccule. Together with the facial and intermediate nerves, it occupies the internal acoustic meatus in the petrous portion of the temporal bone.

The vestibular part is made up of fibers that originate from the sensory neurons of the vestibular ganglion, which conduct balance-related nerve impulses.

The cochlear part consists of fibers that originate from the sensory neurons of the spiral ganglion and conduct hearing-related nerve impulses.

The vestibulo-cochlear nerve fibers are classified as special somatic afferents.

VESTIBULOCOCLEAR NERVE
 
Vestibulocochlear Nerve
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location   Passage
Vestibulocochlear Nerve - Location   Vestibulocochlear Nerve - Passage

IX. Glossopharyngeal Nerve

It is a mixed nerve that emerges from the posterior lateral sulcus of the bulb, in the form of root filaments, which are arranged in a vertical line. These filaments come together to form the trunk of the glossopharyngeal nerve, which exits the skull through the jugular foramen. In its path, through the jugular foramen, the nerve has two upper and lower ganglions formed by sensory neurons. On leaving the skull, the glossopharyngeal nerve is descending, branching at the root of the tongue and pharynx.

Of these, the most important is represented by the general visceral afferent fibers, responsible for the general sensitivity of the posterior third of the tongue, pharynx, uvula, tonsil, auditory tube, besides the carotid sinus and body. Also noteworthy are the general visceral efferent fibers belonging to the parasympathetic division of the autonomic nervous system and ending in the optic ganglion. From this ganglion, nerve fibers exit from the aurio-temporal nerve that will innervate the parotid gland.

GLOSSOSPHARINE NERVE
 
Glossopharyngeal Nerve
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location   Passage
Glossopharyngeal Nerve- Location   Glossopharyngeal Nerve- Passage

X. Vacant Nerve

The vagus nerve is mixed and essentially visceral. It emerges from the posterior lateral sulcus of the bulb in the form of root filaments that come together to form the vagus nerve. It emerges from the skull through the jugular foramen, runs through the neck and chest, ending in the abdomen. In this path, the vagus nerve gives rise to several branches that innervate the pharynx and larynx, entering the formation of visceral plexuses that promote autonomic innervation of the thoracic and abdominal viscera.

The vagus has two sensory ganglia: the upper ganglion, located at the level of the jugular foramen; and the lower ganglion, located just below this foramen. Between the two ganglia, the internal branch of the accessory nerve joins the vagus.

General visceral afferent fibers: Conduct afferent impulses originating in the pharynx, larynx, trachea, esophagus, chest viscera, and abdomen.

General visceral efferent fibers: are responsible for the parasympathetic innervation of the thoracic and abdominal viscera.

Special visceral efferent fibers: innervate the pharynx and larynx muscles.

The efferent fibers of the vagus originate in nuclei located in the bulb, and the sensory fibers in the upper and lower ganglia.

NERVO VAGO
 
Vacant Nerve
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location   Passage
Vacant Nerve - Location   Vacant Nerve - Passage

XI. Accessory Nerve

Formed by a cranial root and a spinal. The spinal root is formed by filaments that emerge from the lateral face of the first five or six cervical segments of the spinal cord, forming a trunk that penetrates the skull through the foramen magnum. To this trunk are attached filaments of the cranial root that emerge from the posterior lateral sulcus of the bulb.

The trunk is divided into an internal and an external branch. The internal joins and is distributed with the vagus, and the external innervates the trapezius and sternocleidomastoid muscles.

The fibers from the cranial root that attach to the vagus are:

 Special visceral efferent fibers, which innervate the larynx muscles;

 General visceral efferent fibers, which innervate thoracic viscera.

NERVE ACCESSORY
 
Accessory Nerve
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location   Passage
Accessory Nerve - Location   Accessory Nerve - Passage

XII. Hypoglossal Nerve

Essentially motor nerve. Emerges from the anterior lateral sulcus of the bulb in the form of root filaments that join to form the nerve trunk. It emerges from the skull through the hypoglossal canal, and addresses the intrinsic and extrinsic muscles of the tongue (it is related to its motricity). Its fibers are considered somatic efferent.

Hypogastric Nerve
Hypogastric Nerve

 

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Location   Passage
Hipoglosso Nerve - Location   Hypoglossal Nerve - Passage

 

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