Nerves are the backbone of the nervous system. Most of them are cranial, that is, they come from the brain. one of these nerves is the trigeminal. What is the anatomy of the trigeminal nerve?
What is this?
The trigeminal nerve in its structure is a nerve of a mixed type. Refers to the 5th 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. Motor innervation is carried out by the motor nucleus, which innervates mainly the masticatory muscles. What is the anatomy of the trigeminal nerve and the localization of its branches?
The nerve exits the brain at the pons. Leaving the brain, most of it passes through the pyramid of the temporal bone. At its top, the nerve divides into three branches: ophthalmic (r.ophthalmicus), maxillary (r.maxillaris) and mandibular (r.mandibularis).
This nerve is of interest to neurologists becauseinnervates the entire area of the face. Quite often, its lesions are observed during hypothermia, injuries of the facial region, and some diseases of the musculoskeletal system.
What is the anatomy of the trigeminal nerve, its branches?
Ocular nerve
The first branch of the trigeminal nerve is the ophthalmic nerve or nervus ophthalmicus.
This is the thinnest branch from the trigeminal nerve. It performs mainly the function of reception. Innervates the skin of the forehead, some parts of the temporal and parietal region, 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 at the outer wall of the ophthalmic sinus, where it gives off branches to the trochlear and abducens nerves. In the region of the superior orbital notch, the nerve divides into three smaller and thinner bundles - the lacrimal, frontal and ciliary nerves.
Their close localization to the eyeball often leads to their defeat as a result of injuries of the orbit or supraorbital region.
The ciliary nerve, in turn, forms the ciliary ganglion, located on the border of the inner and middle thirds of the optic nerve. It consists of parasympathetic nerve endings involved in the innervation of the glands of the eye and the periorbital region.
Maxillary nerve
The other branch of the trigeminal nerve is the maxillary or nervus maxillaris.
He comes out of the cavityskull through the oval window. From it, he enters the pterygo-palatine fossa. Passing in it, the nerve continues into the infraorbital, passing through the lower orbital foramen. After passing through it, the nerve passes in the canal of the same name on the lower wall of the orbit. It enters the face through the lower orbital opening, where it breaks up into smaller branches. They form connections with branches of the facial nerve and innervate the skin of the lower eyelid, upper lip, and lateral surface of the face. In addition, branches from the maxillary nerve include the zygomatic nerve, the superior alveolar branches that form a plexus near the teeth, and the ganglionic branches that connect the maxillary nerve to the pterygopalatine ganglion.
The defeat of this nerve is observed in 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 sensory branches, almost the entire part of the motor root of the trigeminal nerve, coming out of the motor nucleus, nucleus motorius, to the muscles of the lower jaw. As a result of this arrangement, it innervates these muscles, as well as the skin that covers them. The nerve exits the skull through the foramen ovale (oval window or hole), after which it divides into 2 groups of branches:
- muscular branches go to chewing muscles - pterygoid muscle, temporalis; also innervated by musculus digastricus.
- Sensitive branches go to the mucosathe shell of the cheek, as well as to the bottom of the oral cavity. Partially, these branches also innervate the tongue. The largest and longest branch of the mandibular nerve - the inferior alveolar (in other sources - alveolar) nerve, passes through the mental foramen with the artery of the same name and goes into the canal of the mandible, where the inferior alveolar plexus is formed.
It can be considered that this branch continues the trigeminal nerve. 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 inferior alveolar plexus, the entrance to the mandibular canal can be considered the place of its termination.
The course of nerve fibers
What is the anatomy of the trigeminal nerve (the 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 the three major main branches of the trigeminal nerve. The sensitive nerve root penetrates through the middle legs of the cerebellum, where it closes on three nuclei of the brain - the upper and middle, each of which contains specific sensory neurons. The motor part of the nerve starts from the motor nucleus - nucleus motorius.
Due to this arrangement, the nerve can be exposed to bothof 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?
Disorders of the trigeminal nerve
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 channelopathies - infringement of the branches of the nerve passing through the canal or opening by the surrounding formations. In this case, knowledge of the topography of the nerve and some topical signs allows you to determine 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 the nerves. Growing, they contribute to its compression and the appearance of an appropriate clinical picture.
Anatomy of the trigeminal nerve (knowledge of its branches and places of its projection on the face) allows you to determine the exit points of the nerve branches and stimulate them using electrophysiological methods of influence, or, given the location of the branches, to conduct appropriate treatment of the underlying disease that led to the appearance of pathological symptoms.
Trigeminal examination
The study of the function of the trigeminal nerve is carried out in determining the sensitivity of the skin areas that it innervates, as well as the patient's ability to strain and relax the masticatory muscles. The study of the nerve is carried out by palpation of the points of its exit to the face. How to determinehow sensitive is the trigeminal nerve? Its anatomy allows you to determine the activity of sensitive neurons located under the skin.
Determination of sensitivity is carried out with cotton wool or a swab soaked in a cold or hot solution. Pain sensitivity is tested by touching a needle.
To check the motor function, the patient is asked to perform several chewing movements.
In the presence of pathology, there is a change in sensitivity in one or more zones of innervation, or the patient's inability to perform correct chewing movements. There is a deviation of the jaw to the affected side or excessive muscle spasm. The tension in the masticatory 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 the lesion. Knowing where which branch passes, what clinical signs are characteristic of its defeat and how they can be complicated, you can decide on the volume and treatment plan.
Knowing the location and course of the branches of this nerve rests on the shoulders of neurologists and neurosurgeons. It is these specialists who, for the most part, are faced with diseases in which the trigeminal nerve is affected. Anatomy (photo obtained using MRI) allows you to determine the tactics of treatment and take appropriate measures.
When the first signs of defeat of one oranother branch of the nerve, you must immediately seek help from a doctor of the appropriate specialization to determine the diagnosis and draw up a treatment algorithm.
