Nerves are the foundation of the nervous system. Most of them are cranial, that is, they leave the brain. one of these nerves is trigeminal. What is the anatomy of the trigeminal nerve?
What is it?
The trigeminal nerve in its structure is a mixed type nerve. Refers to 5 pair of cranial nerves.
It includes sensitive (afferent, centripetal) and motor (centrifugal) fibers, due to which impulses are transmitted along this nerve from both superficial (pain and temperature) and deep (proprioceptive) receptors. The motor innervation is carried out by the motor core, which innervates mainly the masticatory muscles. What is the anatomy of the trigeminal nerve and the localization of its branches?
A nerve exits the brain in the area of the bridge. Coming out of the brain, most of it passes through the pyramid of the temporal bone. At its apex, the nerve is divided into three branches: the orbital (r.ophthalmicus), maxillary (r.maxillaris) and mandibular (r.mandibularis).
This nerve is of interest to neurologists as it innervates the entire area of the face. Quite often, its lesions are observed during hypothermia, facial trauma, and some diseases of the musculoskeletal system.
What is the anatomy of the trigeminal nerve, its branches?
Orbital nerve
The first branch of the trigeminal nerve is the ophthalmic nerve or nervus ophthalmicus.
This is the thinnest branch extending from the trigeminal nerve. It performs primarily the function of reception. Innervates the skin of the forehead, some parts of the temporal and parietal regions, the upper eyelid, the back of the nose, some sinuses of the facial bones and partially the mucous membrane of the nasal cavity.
The composition of the nerve includes about thirty relatively small bundles of nerve fibers. The nerve enters the orbit near the outer wall of the ophthalmic sinus, where it gives branches to the block and abduction nerves. In the upper orbital notch, the nerve is divided into three smaller and thinner bundles - the lacrimal, frontal and ciliary nerves.
Their close localization to the eyeball often leads to their damage as a result of injuries of the orbit or infraorbital region.
The ciliary nerve, in turn, forms the ciliary ganglion, located on the border of the inner and middle third of the optic nerve. It includes parasympathetic nerve endings involved in the innervation of the glands of the eye and the periorbital region.
Maxillary nerve
Another branch of the trigeminal nerve is the maxillary or nervus maxillaris.
He leaves the cranial cavity through an oval window. From it he enters the pterygo-palatine fossa. Passing in it, the nerve continues into the lower orbital, passing through the lower orbital foramen. After passing through it, the nerve passes in the channel of the same name on the lower wall of the orbit. On the face, he goes through the lower orbital foramen, where it splits into smaller branches. They form connections with the branches of the facial nerve and innervate the skin of the lower eyelid, upper lip and lateral surface of the face. In addition, branches extend from the maxillary nerve, such as the zygomatic nerve, the upper alveolar branches that form the plexus near the teeth, and the ganglionic branches connecting the maxillary nerve with the pterygo-palatine ganglion.
The defeat of this nerve is observed with massive facial injuries, neuritis, operations on the teeth and sinuses.
Mandibular nerve
The third and most complex branch of the trigeminal nerve is the mandibular or nervus mandibularis. In its composition, it has, in addition to sensitive branches, almost the entire part of the motor root of the trigeminal nerve, emerging from the motor nucleus, nucleus motorius, to the muscles of the lower jaw. As a result of this arrangement, these muscles innervate, as well as the skin that covers them. The nerve leaves the skull through the foramen ovale (oval window or hole), after which it is divided into 2 groups of branches:
- muscle branches go to the masticatory muscles - pterygoid muscle, temporal muscle; musculus digastricus is also innervated.
- Sensitive branches go to the mucous membrane of the cheek, as well as to the bottom of the oral cavity. Partially, these branches innervate the language as well. The largest and longest branch of the mandibular nerve - the lower alveolar (in other sources - the alveolar) nerve, passes through the chin hole with the same artery and goes into the channel of the lower jaw, where the lower alveolar plexus is formed.
We can assume that the trigeminal nerve continues with this particular branch. The anatomy, the scheme of this nerve (structure) and its properties (mixed nerve fiber) allow us to consider this branch as terminal. Despite the fact that it forms the lower alveolar nerve plexus, the entrance to the mandibular canal can be considered the place of its end.
The course of nerve fibers
What is the anatomy of the trigeminal nerve (structure and course of its branches)?
The structure of the trigeminal nerve is similar to that of any of the spinal nerves. The trigeminal nerve has a special large node - the trigeminal ganglion. This formation is located in the middle cranial fossa. From all sides it is surrounded by sheets of the dura mater. The node has dendrites that form three large main branches of the trigeminal nerve. The sensitive root of the nerve penetrates through the middle legs of the cerebellum, where it closes on the three nuclei of the brain - the upper and middle, each of which contains specific sensitive neurons. The motor part of the nerve begins from the motor nucleus - nucleus motorius.
Due to this arrangement, the nerve can be affected by both the brain and surrounding tissues, which is why it is of particular interest to neurologists.
What are the main types of lesions characteristic of the nerve?
Trigeminal diseases
What processes affect the functional ability of this formation, and how can the trigeminal nerve be affected?
The anatomy of its course predisposes to the development of canalopathies - the infringement of the branches of a nerve that passes through a canal or opening, by surrounding formations. In this case, knowledge of the topography of the nerve and some topical features allows you to establish the level of damage to it and take appropriate measures.
Another, equally important factor is the influence of surrounding tissues. Most often, brain tumors affect nerves. Growing, they contribute to its compression and the appearance of the corresponding clinical picture.
The anatomy of the trigeminal nerve (knowledge of its branches and the places of its projection on the face) allows you to determine the exit sites of the nerve branches and stimulate them by electrophysiological methods of exposure, or, given the location of the branches, conduct appropriate treatment of the underlying disease, which led to the appearance of pathological symptoms.
Trigeminal Examination
A study of trigeminal nerve function is carried out in determining the sensitivity of the skin areas that it innervates, as well as in the patient's ability to strain and relax the masticatory muscles. Examination of the nerve is carried out by palpation of the points of its exit to the face. How to determine how sensitive the trigeminal nerve? Its anatomy allows you to determine the activity of sensitive neurons located under the skin.
The determination of sensitivity is carried out with cotton wool or a swab dipped in a cold or hot solution. Pain sensitivity is checked by touching the needle.
To check the motor function, the patient is asked to perform several chewing movements.
In the presence of pathology, a change in sensitivity is observed in one or more zones of innervation, or the patient's inability to make proper chewing movements. There is a deviation of the jaw to the sore side or excessive muscle spasm. The tension in the chewing muscles is determined by pressing them during the act of chewing.
Why you need to know topography
Topographic anatomy of the trigeminal nerve is necessary to accurately determine the site of damage. Knowing where the branch goes, what clinical signs are characteristic of its lesion and how they may be complicated, you can determine the volume and plan of treatment.
Knowledge of the location and course of the branches of this nerve lies on the shoulders of neurologists and neurosurgeons. It is these specialists who mostly encounter diseases in which the trigeminal nerve is affected. Anatomy (photo obtained by MRI) allows you to determine the tactics of treatment and take appropriate measures.
When the first signs of damage to a particular nerve branch appear, you should immediately seek help from a doctor of the appropriate specialization to determine the diagnosis and draw up a treatment algorithm.