Cranial nerves, 12 pairs: anatomy, table, functions
Nerves entering and leaving the brain in medicine are defined as cranial or cranial nerves( 12 pairs).They innervate the glands, muscles, skin and other organs located in the region of the head and neck, as well as in the abdominal and thoracic cavity.
Let's talk about these pairs and the violations that arise in them today.
Types of cranial nerves
Each of these pairs of nerves is denoted by a Roman numeral from the first to the twelfth, according to their location on the basis of the brain. They are arranged in the following order:
These include vegetative, efferent and afferent fibers, and their nuclei are located in the gray matter of the brain. Depending on the composition of nerve fibers, all cranial nerves( 12 pairs) are divided into sensitive, motor and mixed. Consider them in this aspect.
This group includes the olfactory, visual and auditory nerves.
Olfactory nerves have processes that are located in the nasal mucosa. Starting from the nasal cavity, they cross the trellis plate and approach the olfactory bulb, where the first neuron ends and the central path begins.
The visual pair consists of fibers that depart from the retina, cones and rods. All nerves enter into one trunk in the cavity of the skull. First they form a cross, and then the visual path, enveloping the leg of the brain and giving fiber to the visual centers. One nerve contains about a million fibers( axons of the neurons of the eye retina) and, in addition, it has one vagina from the outside, and the other - inside. The nerve penetrates the skull through the visual canal.
The auditory cranial nerves refer to the eighth pair - 12 pairs of the rest, except these three, are motor or mixed. In the auditory nerves, the fibers are directed from the middle ear to the cores. In each of them enters the vestibule and cochlea root. They move away from the middle ear and enter the bridge-medullar angle.
Another group of 12 pairs of cranial nerves includes oculomotor, block, additional, sublingual and distracting nerves.
The third pair, that is, the oculomotor nerves, contains vegetative, motor and parasympathetic fibers. They are divided into upper and lower branches. Moreover, only the upper branches belong to the motor group. They enter the muscle that lifts the eyelid.
The following group includes the block nerves, which move the eyes into motion. If you compare all the cranial nerves - 12 pairs - then these are the thinnest. They originate from the core on the midbrain, then go around the stem of the brain and go to the orbit, innervating the upper oblique muscle of the apple of the eye.
Absorbing nerves are related to the direct eye muscle. They have a motor nucleus in the pit. When they leave the brain they go to the upper glandular gap, innervating the straight eye muscle there.
Additional nerves originate from the medulla oblongata and cervical spinal cord. Separate roots are connected in one trunk, passing through the hole and dividing into the outer and inner branches. The internal branch, in which there are fibers involved in the innervation of the larynx and pharynx, it is attached to the vagus nerve.
And the last of 12 pairs of cranial nerves( the table of which for convenience is presented at the end of the article), related to motor nerves, are sublingual nerves. The origin of this nerve is spinal. But, eventually, his spine moved to the skull. It is clear that this is the motor nerve of the tongue. The roots come out of the medulla oblongata, then cross the carotid artery and enter the lingual musculature, dividing into branches.
This group includes the trigeminal, facial, glossopharyngeal and vagus nerves. In mixed nerves, there are ganglia similar to those that are found in spinal nerves, but they do not have anterior and posterior roots. They fibers of motor and sensitive types are connected to the common trunk. Also they can just be near.
The output of 12 pairs of cranial nerves is different. Thus, the third, seventh, ninth and tenth pairs have parasympathetic fibers at the output sites, which are directed toward the vegetative ganglia. Many of them are united by branches, where different fibers pass.
The tee nerve has two roots, where the larger one is sensitive, and the smaller one - motor. Innervation of the skin occurs on the parietal, ear and chin areas. Innervation also captures the conjunctiva and the apple of the eye, the hard shell of the brain, the mucous membrane - of the mouth and nose, teeth and gums, and the main part of the tongue.
Ternary nerves come between the cerebellar pedicle, in the middle, and the bridge. Fibers of the sensitive root refer to the ganglion, lying in the temporal pyramid near the apex, which was formed as a result of the cleavage of the solid membrane of the brain. They end in the nucleus of this nerve, which is in the pit, as well as the nucleus of the spinal path, continuing into the medulla oblongata, and then heading into the spinal cord. Fibers of the spine of the motor nerve originate from the trigeminal nucleus, which is located in the bridge.
From the ganglion, the upper, lower jaw and ocular nerves. The latter is sensitive, divided into a nosoreschnic, frontal and lacrimal. The innervation of 12 pairs of cranial nerves differs not only in the pairs themselves, but also in the derived branches. Thus, the lacrimal nerve innervates the lateral eye angle, transmitting the secretory branches of the lacrimal gland. The frontal nerve, respectively, branched out on the forehead and supplies it with a mucous membrane. The nosoresnichny innervates the eyeball, and from it depart the latticed nerves, innervating the mucous membrane of the nose.
The maxillary nerve is also sensitive, passing into the pterygopalatine fossa and reaching the front face. From it originate the upper alveolar nerves, which pass to the teeth of the upper jaw and gums. The nerve on the cheekbones runs from the ganglion along the back nerves of the nose to its mucous and nasopharynx. Nerve fibers are sympathetic and parasympathetic.
Mixed type refers to the mandibular nerve. It consists of the motor spine. Its sensitive branches include the buccal nerve, which supplies the corresponding mucous membrane, ear-temporal, innervating the skin on the temples and ears and lingual, which supplies the tip and back of the tongue. The lower alveolar nerve is mixed. Passing in the lower jaw, it ends on the chin, branched here in the skin and mucous of the lower lip. The branches in it are associated with autonomic ganglia:
- an ear-temporal nerve - with the ear, innervating the parotid gland;
- lingual nerve - with a ganglion giving innervation to the sublingual and submandibular glands.
To the facial include motor and sensitive cranial nerves. Mixed fibers create a sense of taste. Some fibers here innervate tear and salivary glands, and others - the front two-thirds of the tongue.
The facial nerve consists of motor fibers starting in the upper fossa. It includes an intermediate nerve with taste and parasympathetic fibers. Some are the processes of the ganglion, ending with the taste fibers of the vagus and glossopharyngeal nerves. And others begin in the salivary and lacrimal nuclei, located next to the motor nucleus.
The facial nerve begins in the cerebro-cerebral corner of the brain, and then passes into the facial canal through the auditory canal. Here is the drum string and, passing through the cavity, connects to the lingual nerve. It includes taste and parasympathetic fibers that reach the submaxillary ganglion.
The facial nerve emerges from the bone of the temples and passes into the parotid gland, weaving there. Hence the branches diverge in a fan-like fashion. At this time, all muscles belonging to mimic nerves are innervated, and some others. The branch on the neck from the facial nerve branches into it in the subcutaneous muscle.
The glomeropharyngeal pair realizes the innervation of the lacrimal glands, the posterior portion of the tongue, the inner ear and the pharynx. The motor fibers are directed toward the shihlogochnoy muscle and the compressors of the pharynx, and the sensitive fibers are directed to the parotid gland to the ear ganglion. The nuclei of these nerves, in contrast to where the other nuclei of 12 pairs of cranial nerves are located, are located in the pit - the triangle of the vagus nerve.
Parasympathetic fibers begin in the salivary nucleus. The glossopharyngeal nerve, moving away from the medulla oblongata, stretches to the base of the tongue. From the ganglion begins the tympanic nerve, which has parasympathetic fibers, extending to the ear ganglion. Further, lingual, amygdala and pharyngeal nerves begin. The lingual nerves innervate the root of the tongue.
The wandering couple realizes parasympathetic innervation in the abdominal cavity, as well as in the chest and neck area. This nerve includes motor and sensitive fibers. Here the greatest innervation. The wandering nerve has a double core:
- single path.
Leaving behind the olive on the neck, it moves with a neuromuscular bundle, and then branches.
Functional dysfunctions can have all cranial nerves - 12 pairs. Anatomy of lesions is manifested at different levels of nuclei or trunks. To diagnose, an in-depth analysis of intracranial pathological processes is conducted. If the lesion affects one side of the nuclei and fibers, then most likely, it is a violation of the functions of any of the affected 12 pairs of cranial nerves.
Neurology studies, however, the symptoms on the opposite side. Then the lesion of the conducting paths is diagnosed. It also happens that the disturbances in the functions of the nerves are connected also with a tumor, an arachnoid cyst, an abscess, vascular malformations and other similar processes.
Simultaneous defeat of 12 pairs of cranial nerves, that is, sublingual, as well as vagal and glossopharyngeal, has received the name of bulbar paralysis. This is a very dangerous disease, since there is a possibility of pathology of the most important centers of the brain stem.
Knowledge of the topographic location of the cranial nerves allows to correctly identify a narrow area of destruction of each of them. To conduct research, use special techniques. With appropriate equipment, it is now possible to reveal all the details of the status of the fundus, optic nerve, diagnose the field of vision and foci of prolapse. Computerized research allows highly accurate localization of the lesion site.
Ophthalmic examination of
This technique allows to reveal abnormalities in the work of oculomotor, block and withdrawing pairs of nerves, to reveal limited motor activity of eyeballs, the degree of exophthalmos and others. The pathology of the visual and auditory nerves can be caused by the narrowing of the canal in the bone or, conversely, its expansion. Diagnosis of the upper slot of the orbit, as well as various holes in the skull, is performed.
Vertebal and carotid angiography
This method is important in the recognition of vascular malformations and intracranial processes. Nevertheless, more detailed information on these issues will provide a computed tomography. It visualizes the trunks of the cranial nerves, diagnoses the tumor of the visual and auditory couple and other pathologies.
The deepening of the study of cranial nerves became possible due to the development of this method. It determines the state of spontaneous muscular masticatory and facial activity, the muscles of the tongue, the soft palate and other muscles. Electromyography also makes it possible to calculate the speed of impulse conduction along the trunks of facial, accessory and sublingual nerves. For this, a reflex blinking response is investigated, which is provided by trigeminal and facial nerves.
Neurological examination and symptoms of the disorder of individual cranial nerves
This procedure is carried out in a certain order. The examination begins with the olfactory nerve. The cotton wool soaked in the irritant is brought to the nostrils alternately. The optic nerve is examined on an ophthalmologic examination, on the basis of which, in addition to direct lesion, it is possible to detect even secondary changes. Pathology can be stagnant, dystrophic, inflammatory or the nerve can be destroyed completely.
The lesions of the next three of the 12 pairs of cranial nerves( oculomotor, outflow and block) cause diplopia and strabismus. There may also be a descent of the upper eyelid, a dilated pupil, double vision.
Violations in the fifth pair, that is, in trigeminal nerves, lead to a worsening of sensitivity on that part of the face where they are present. This can be observed both in the region of the temples, forehead, and cheekbones, eyes, chin and lips. It happens that there is a lot of pain, there are rashes and other reactions. In view of the fact that the facial nerves have many connections, this pair is characterized by a wide variety of pathological reactions.
If the auditory nerve is impaired hearing deteriorates, glossopharyngeal - the sensitivity in the inner ear, sublingual - the movement of the tongue is limited. In the case of the vagus nerve, paralysis of the soft palate or vocal cords develops. In addition, the rhythm of the heart, respiration, and other visceral-vegetative functions may be disturbed.
Complex disorders and cranial nerves( 12 pairs): anatomy, table
Functions of nerve fibers can be broken both in isolation and in a complex, together with different pathologies of the lower skull. So, if all nerves are affected on one half of the cranial base, then talk about the syndrome of Garcena. At a tumor of orbital bones and soft tissues there is a syndrome of the top orbital crack. With defeat and the embrace, and the optic nerves, Kennedy's syndrome arises.
These and other diseases occur both in adulthood and in childhood. For children, lesions of nerves are especially common, which are associated with developmental malformations.
Below is a structure on which you can better understand how the cranial nerves( 12 pairs) operate. Anatomy( the table is based on her knowledge) will help you navigate the intricacies of the functioning of their different groups.
We examined all the cranial nerves - 12 pairs. The anatomy, the table, the functions given in the article demonstrate that all the brain-nerve nerves have a complex structure closely related to each other. And if any function is implemented with a restriction or not performed at all, then there are violations.
Well helps to master all cranial nerves( 12 pairs) table. Neurology, using these data, and also thanks to special modern equipment, has made significant progress in the possibilities of timely diagnosis and effective treatment of patients.