Trigeminal Nerve V Cranial Nerve

The trigeminal nerve is mixed, mainly sensitive, and containing general somatic afferent (GSA) and motor special visceral efferent (SVE) fibers. It derives from the reunion of three branches: ophthalmic (VI), maxillary (V2) and mandibular (V3). The ophthalmic nerve derives from the conjunction of three main branches: lacrimal, frontal and nasociliary. It carries sensitivity from the upper face and the eye, penetrates the skull through the superior orbital fissure and forms the VI nerve. This passes through the cavernous sinus and reaches Meckel's cave, where the trigeminal ganglion (or Gasser's or semilunar ganglion) is located. The sensitivity of the maxillary region and the upper teeth is carried by the maxillary nerve. It passes through the foramen rotun-dum, enters the cavernous sinus and reaches the Gasserian ganglion. The mixed component is represented by the 3rd branch, the mandibular nerve. It carries sensitivity from the mandibular region of the face and the lower teeth and receives the meningeal branch through the foramen spinosum. Moreover, it carries motor fibers mostly directed to masticator muscles (temporal, masseter and pterygoid) and the tensor veli palatini and tensor timpani muscles. The three branches join together in Gasserian ganglion. This is a plex-iform structure, located in a proper cistern inside Meckel's cave. The preponderance of CSF makes the MR signal of the ganglion CSF-like in T2-w sequences. The GSA component of the trigeminal nerve, with a voluminous root, penetrates the pons' lateral part, at the edge toward the middle cerebellar peduncle, crosses the tegmentum, and ends in the sensory nuclei of the pons and bulb: mesecenphalic nucleus, main sensory nucleus and nucleus spinalis, where a definite topographic organization exists: ophthalmic fibers are more ventral; mandibular dorsal and maxillary ones are intermediate.

The nerve's special visceral efferent (SVE) component originates from the motor nucleus at the level of the pons, and exits medially at the access of the sensory root.

The mesencephalic nucleus of the trigeminal nerve is near the lateral edge of the gray matter of the fourth ventricle's andand sylvian aqueduct's upper parts. Here, proprioceptive impulses (of pressure and kinaesthesia) arrive from teeth, periodontium, hard palate, and capsulae articulares.

The main sensory nucleus is placed laterally at the access of the trigeminal nerve's radicular fibers in the upper part of the pons and receives general somatic afferent (GSA) fibers, transporting impulses for touch and pressure.

The spinal tract extends from the level of the trigeminal nerve's root in the pons to upper cervical spinal segments. It receives impulses from the internal structures of nose and mouth, from the cutaneous facial regions, forehead, cheeks and jawbone, and contains small groups of fibers with GSA components coming from the VII, IX and X nerves.

The motor nucleus (masticator nucleus) is placed medially between the motor root and the main sensory nucleus. It receives collaterals from the mesencephalic and main sensory nuclei and from the nucleus of the VIII nerve.

The sensory nuclei of the trigeminal nerve (principal and spinal) show connections to the reticular formation of the bulb, to the cerebellum (through the inferior cerebral peduncle), and to the nucleus ventralis posteromedial thalami of the opposite side (ventral thalamic trigeminal tract) and of the same side (dorsal trigeminal tract).

The mesencephalic nucleus projects to the cerebellum. It is also connected to the nuclei of XII, XI, X, IX, VI! and V nerves for corneal, lacrimal, sneezing, vomiting, salivary and oculocardiac reflexes.

Accessory oculomotor nucleus

Oculomotor nucleus

Trochlear nucleus

Abducent nucleus

III Cranial Nerve: Oculomotor Nerve

III Cranial Nerve: Oculomotor Nerve

Posterior cerebral arteries

III cranial nerve, cavernous portion

VI cranial nerve, cavernous portion

III cranial nerve, cavernous portion

VI cranial nerve, cavernous portion

Cavernous sinus

Lateral wall of the cavernous sinus: dural folder

Posterior cerebral artery

Internal carotid artery

Posterior cerebral artery Dorello's canal - VI cranial nerve

Posterior cerebral artery

Internal carotid artery

Posterior cerebral artery Dorello's canal - VI cranial nerve

Cavernous sinus

Lateral wall of the cavernous sinus: dural folder

VI Cranial Nerve: Abducent Nerve

Emergence at the pontomedullary sulcus

VI Cranial Nerve: Abducent Nerve

Emergence at the pontomedullary sulcus

Cisternal portion at the mid-level of the pons

Entry into the cavernous sinus through Dorello's canal

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