Human medulla oblongata and its most important functions. Structure and functions of the medulla oblongata: symptoms of damage Medulla oblongata structure and functions anatomy

The medulla oblongata is an important link in the structure of the brain. Together with other components, it forms the brain stem and performs a number of vital functions for a living organism.

The most important function of the medulla oblongata, without which the existence of a living organism is impossible, should include the formation and support of autonomic reflexes.

Irritations coming through the nerve fibers from the medulla oblongata to various parts and organs of the body lead to the occurrence of such processes as heartbeat, respiration, digestion, cutaneous and vascular phenomena, to the beginning or end of the digestion process, to blinking of the eyelids and lacrimation, lacrimation, cough , vomiting and many others.

In addition to autonomic reflexes, the medulla oblongata is also responsible for the somatic unconditioned reactions of the human body. It determines muscle tone, balance support, coordination of movements and the work of the entire human motor apparatus. Under the influence of commands from the medulla oblongata, the newborn child unconsciously begins to suck on the mother's breast.

In addition to independently generating various nerve impulses, the medulla oblongata also provides a strong neural connection between the spinal cord and various parts of the brain and is the physical boundary between these two organs of the central nervous system.

Structure of the medulla oblongata

The medulla oblongata is located directly next to the spinal cord on one side, and on the other side it connects to the hindbrain. It has the shape of an inverted truncated cone. The base of this cone, which is large in area, is located at the top, and narrowing begins in the downward direction. Due to its characteristic expanded shape with a smooth narrowing, in medicine it is sometimes called bulbus, which means bulb.

Despite its small size, only up to 25 mm for an adult, the medulla oblongata has a heterogeneous structure. Inside it is gray matter, surrounded on the periphery by separate clots - nuclei. Outside, a series of surfaces separated from each other by furrows can be clearly distinguished.

Ventral surface

In front, on the outer part of the medulla oblongata directed towards the skull along its entire length, the ventral surface is located. This surface is divided into two parts by a vertical anterior median fissure passing in the middle, connected to the median fissure of the spinal cord.

Two convex rollers located along the gap on both sides are called pyramids. They contain bundles of fibers, which also smoothly pass into the fibers of the spinal cord.

On the opposite side of the slit of the pyramids in the upper part of the medulla oblongata there is another elevation, which, because of their characteristic shape, is called olives. Olives are a link between the spinal cord and the cerebellum, and also connects them with certain parts of the brain responsible for the coordination of movements and muscle work, the so-called reticular formation.

Dorsal surface

The posterior surface of the medulla oblongata, directed inside the cranium, is called the dorsal surface. It is also divided by the median sulcus and has roller-like thickenings of fiber bundles for communication with the spinal cord.

Side surfaces

Between the ventral and dorsal surfaces are two lateral surfaces. Each of them is clearly separated by two lateral furrows. These furrows are a continuation of the same furrows extending from the spinal cord.

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Chapter 3

Axes and planes of the human body - The human body consists of certain topographic parts and areas in which organs, muscles, blood vessels, nerves, etc. are located.

Wall trimming and jamb cutting - When the house lacks windows and doors, a beautiful high porch is still only in the imagination, you have to climb the stairs from the street into the house.

Second Order Differential Equations (Price Forecast Market Model) - In simple market models, supply and demand are usually assumed to depend only on the current price of a commodity.

Medulla- the most caudal part of the brainstem, located between the spinal cord and the bridge. The nuclei of the V-XII pairs of cranial nerves are located in the medulla oblongata, separated by pathways passing through the medulla oblongata, both in the ascending and descending directions.

Reticular formation- an accumulation of neurons with specific properties, the bulk of which occupies the central part of the medulla oblongata. In the lower part of the medulla oblongata on its dorsal side are the nuclei of the tender and sphenoid cords (Goll and Burdakh).

Functions of the medulla oblongata:

Protective reflexes (eg coughing, sneezing); Vital reflexes (eg, breathing); regulation of vascular tone.

Reflex centers of the medulla oblongata: digestion; cardiac activity; protective (coughing, sneezing, etc.); centers for the regulation of skeletal muscle tone to maintain a person's posture .; shortening or lengthening of the spinal reflex time.

reflexes, carried out by its structures, can be divided into vegetative, somatic, reflexes of the implementation of sensory functions (taste, hearing, vestibular reception).

Separately distinguished functions of the medulla oblongata, due to the presence of a reticular formation in it and associated with the regulation of respiration, cardiovascular activity and tonic effects on the spinal cord and cerebral cortex.

pair of VIII cranial nerves - vestibulocochlear nerve consists of cochlear and vestibular parts. The cochlear nucleus lies in the medulla oblongata;

pair IX - glossopharyngeal nerve, its core is formed by 3 parts - motor, sensory and vegetative. The motor part is involved in the innervation of the muscles of the pharynx and oral cavity, the sensitive part receives information from the taste receptors of the posterior third of the tongue; autonomic innervates the salivary glands;

pair X - vagus nerve has 3 nuclei: autonomic innervates the larynx, esophagus, heart, stomach, intestines, digestive glands; sensitive receives information from the receptors of the alveoli of the lungs and other internal organs, and motor (the so-called mutual) provides a sequence of contraction of the muscles of the pharynx, larynx when swallowing;

pair XI - accessory nerve; its nucleus is partially located in the medulla oblongata;

pair XII - hypoglossal nerve is the motor nerve of the tongue, its nucleus is mostly located in the medulla oblongata.

Reflexes:

Vegetative: smooth muscle contraction, secretion - vagus nerve

Somatic: perception, processing, swallowing food, maintaining posture, protection (vomiting, sneezing, coughing, blinking) - glossopharyngeal nerve, accessory nerve, hypoglossal nerve.

Statokinetic: maintaining posture during movement - vestibulocochlear nerve.

12. Integrative functions of the midbrain

midbrain- part of the brain stem, located between the bridge and the diencephalon.

The midbrain contains:

conducting paths,

Nuclei of cranial nerves (pair IV - trochlear nerve; pair III - oculomotor nerve),

reticular formation,

The quadrigemina (superior tubercles - vision; inferior tubercles - hearing),

Midbrain nuclei (substance black and nucleus red)

Superior tubercles of the quadrigemina:

Approximate alertness reflex, pupillary, accommodative, convergence of the eye axes, turn of the eyes, torso to the light source

Inferior tubercles of the quadrigemina:

Ear alertness, turning of the head and body towards the sound source

Red cores:

They receive impulses from the cerebral cortex, subcortical motor nuclei and cerebellum along descending pathways and transmit signals to rubrospinal pathways to spinal cord neurons.

involved in the regulation of muscle tone

Black substance:

coordinates the acts of chewing and swallowing, also participating in the regulation of plastic tone, and in humans - in small movements of the fingers

The midbrain level of the central nervous system provides:

processing of sensory information; motor regulation; modulation of activity and diencephalic-cortical and bulbar-spinal levels

13. Functions and connections of the thalamus

Thalamus - analysis of afferent signals; organization of integrative processes; regulation of the functional state and higher nervous activity.

It consists of specific and non-specific nuclei(morphologically and functionally connected with many systems and participate together with the reticular formation of the brain stem in the implementation of non-specific functions)

Specific nuclei have a local projection to strictly defined areas of the cortex. In them, afferent impulses are switched from peripheral receptors or from the primary perceiving nuclei of the underlying stem structures, as well as from extrasensory sources. Resolution is an irreversible loss of sensation or impaired movement.

These two thalamocortical systems are in constant interaction.

a non-specific system enhances a specific one, and a specific one, on the contrary, suppresses a non-specific one.

Under the influence of nonspecific impulses, the response of cortical neurons to specific stimulation is noticeably enhanced; nonspecific thalamic impulses facilitate the activity of cortical neurons, increasing their excitability.

Primary processing of visual, auditory, tactile and information and a sense of balance and balance.

14. Hypothalamus. Location and functions

Hypothalamus or hypothalamus - a section of the diencephalon located below the thalamus, or "visual hillocks", for which it got its name - is the highest subcortical center for the integration of autonomic, emotional and motor components of complex reactions.

Includes centers that organize homeostasis (maintaining the constancy of the internal environment) and homeokinesis (adaptation of the internal environment to changes in living conditions)

Centers of the hypothalamus: thermoregulation, hunger and satiety, thirst, regulation of sexual behavior, pleasure, displeasure.

Topic 9. Medulla oblongata.

In the brain, from bottom to top, 5 sections are distinguished: oblong, hind, middle, intermediate and final brain.

Rice. 1. Sagittal section of the brain.

1 - medulla oblongata; 2 - hindbrain (bridge and cerebellum); 3 - midbrain; 4 - diencephalon; 5 - telencephalon.

Medulla(medulla oblongata) is a direct continuation of the spinal cord and has a cone shape. It combines the features of the structure of the spinal cord and brain.

Human medulla oblongata and its most important functions

There are ventral, dorsal and lateral surfaces.

The lower border on the ventral surface is the exit point of the roots of the first pair of cervical nerves of the spinal cord, the upper one is the lower edge of the bridge.

On the ventral surface there is a deep median fissure, which is a continuation of the fissure of the same name in the spinal cord. On the sides of it are two longitudinal rollers - pyramids(pyramides), formed by the nerve fibers of the pyramidal tracts, which in the depths of the gap at the border with the spinal cord form a cross (decussatio pytamidum). On the side of the pyramids is the anterior lateral groove, from which the roots of the hypoglossal nerve emerge. In the upper part of the furrow there are convex oval formations - olives(olivae). Lateral to the olive, the posterior lateral sulcus of the medulla oblongata passes, from which the roots of the accessory, vagus, and glossopharyngeal nerves emerge.

Fig.2. Cross section of the medulla oblongata at the level of the inferior olives (view from the ventral surface).

1 - anterior median fissure; 2 - anterolateral furrow; 3 - pyramids; 4 - olives; 5 - the core of the lower olive; 6 - gates of the core of the lower olive; 7 - diamond-shaped fossa; 8 - lower leg of the cerebellum; 9 - reticular formation; 10 - double core; 11 - glossopharyngeal nerve; 12 - vagus nerve; 13 - accessory nerve; 14 - hypoglossal nerve

The dorsal surface of the medulla oblongata has a different structure in the lower and upper parts. In its lower third, it is divided by the posterior median sulcus into two symmetrical parts and contains the continuation of the gentle and wedge-shaped bundles running in the posterior cords of the spinal cord, which end in two protruding tubercles of the nuclei of the same name. Approximately in the middle of the medulla oblongata, the right and left posterior cords diverge up and to the side and pass into thick rollers - the lower legs of the cerebellum, which are immersed in the cerebellum. The upper part of the dorsal surface of the medulla oblongata is deployed, forming the lower half rhomboid fossa. A median groove runs along the bottom of the rhomboid fossa, on the sides of which there are elevations - triangles of the vagus and hypoglossal nerves. In the lateral sections of the fossa, on the border with the bridge, there is vestibular field, in the depths of which are the auditory and vestibular nuclei.

Fig.3. Dorsal surface of the medulla oblongata.

1 - diamond-shaped fossa; 2 - brain strips; 3 - posterior median sulcus; 4 - posterolateral furrow; 5 - posterior intermediate furrow; 6 - thin beam; 7 - tubercle of a thin bundle; 8 - wedge-shaped bundle; 9 - tubercle of the wedge-shaped bundle; 10 - lateral cord; 11 - the lower leg of the cerebellum.

The lateral surface of the medulla oblongata contains a continuation of the lateral cords of the spinal cord and ends in the upper section with the trigeminal tubercle.

The internal structure of the medulla oblongata. If a transverse section of the medulla oblongata is made at the level of the middle of the olives, a number of structures will be visible on the cut (Fig. 2). Gray and white matter take part in the formation of the medulla oblongata, and as you move up, the nature of their relative position gradually changes. Gray matter gradually loses the shape of a butterfly and is divided by pathways into separate nuclei.

There are four groups of nuclei of the medulla oblongata. The first group is the nuclei of the posterior cords, thin and wedge-shaped located in the thickness of the hillocks of the same name. On the neurons of these nuclei, the fibers of the thin and wedge-shaped bundles end, transmitting information from the proprioreceptors of the body and limbs. The axons of the cells of the thin and wedge-shaped nuclei form two ascending tracts: the larger one is bulbothalamic, which in the form of a medial loop goes to the nuclei of the thalamus and bulbo-cerebellar, which is sent to the cerebellum as part of the lower legs of the cerebellum.

The second group of nuclei - olive kernels. Descending fibers coming from the red nucleus of the midbrain end on the neurons of this nucleus. Functionally, the core is associated with maintaining posture and balance and is part of the extrapyramidal system. From it begins a large olive-cerebellar path, heading to the cerebellum as part of the lower cerebellar peduncles, and a smaller olive-spinal path descending into the spinal cord.

The third group of nuclei is represented by the nuclei of the cranial nerves. In the depths of the medulla oblongata lie the nuclei of the YIII-XII pair of cranial nerves. They are mainly located on the dorsal surface of the medulla oblongata in the region of the rhomboid fossa. Nuclei vestibulocochlear nerve (YIII pair) lie in the lateral parts of the rhomboid fossa in the region of the vestibular field. They are divided into 4 vestibular nuclei and 2 cochlear (auditory). The auditory nuclei (ventral and dorsal) lie in the lateral part of the auditory field. On their cells, the axons of neurons of the spiral ganglion end, through which information is transmitted from the organ of hearing (cochlea). The axons of the neurons of the auditory nuclei are sent to the nuclei of the trapezoid body of the bridge. Three vestibular nuclei (lateral, medial and lower) are also located at the level of the medulla oblongata, the fourth - the upper vestibular nucleus, is considered as part of the nuclei of the bridge. They receive information from the receptors of the semicircular canals, the organ of balance, through the axons of the vestibular ganglion. The vestibular nuclei are distinguished by an abundance of exits. From them begin vestibulo-spinal and vestibulo-cerebellar pathways functionally associated with the coordination of skeletal muscle activity depending on vestibular afferentation. Part of the bundles responsible for visual-motor coordination (image stabilization on the retina) goes to the nuclei III, IY and YI of cranial nerve pairs. There are also pathways to the reticular formation and thalamus. Glossopharyngeal nerve (IX pair)- mixed: has a sensitive, motor and autonomic nuclei located in the medulla oblongata. The sensory nucleus of the glossopharyngeal nerve is single path core(n. solitarius), which stretches along the wall of the IV ventricle in the dorsal part of the medulla oblongata. This nucleus is the common sensory nucleus for the YII, IX and X pairs of cranial nerves. This nucleus collects information from the taste buds of the tongue, as well as from the receptors of the internal organs and the eardrum. Afferents of the nucleus are sent to the thalamus and hypothalamus, as well as to the motor nuclei of the cranial nerves and to the reticular formation. motor core - double core(n. ambiguous), located in the ventrolateral parts of the medulla oblongata. It is a common motor nucleus for the IX and X pairs of cranial nerves. It has inputs from sensory nuclei Y, IX and X pairs of cranial nerves, as well as from the cerebral cortex. The axons of the neurons of this nucleus end on motor neurons that innervate the muscles of the larynx and pharynx. Participates in the implementation of sneezing, swallowing and coughing. The cortical input provides voluntary muscle activity and coordination during speech. The vegetative nucleus is called inferior salivary nucleus(n. salivatorius inferior). It receives axons from neurons of the nucleus of the solitary tract and vestibular nuclei, as well as from neurons of the cerebral cortex. The nucleus regulates the work of the parotid glands. X pair — nervus vagus(n. vagus) - also mixed: motor, sensory, vegetative. The motor nucleus is dual, and the sensory nucleus of the solitary pathway has been discussed above. Vegetative nucleus - posterior nucleus of the vagus nerve, is located on the dorsal surface of the medulla oblongata in the region of the triangle of the vagus nerve.

On the neurons of this nucleus, the axons of the neurons of the nucleus of the solitary pathway and the sensory nuclei of the trigeminal nerve end. The axons of the vagus neurons end on the neurons of the parasympathetic ganglia of the internal organs of the abdominal and thoracic cavities. The nucleus is involved in the regulation of the work of internal organs, carries out the gag reflex. XI pair - accessory nerve(n. accessorius) - motor. The nucleus is located medially in the lower corner of the rhomboid fossa, connected with the anterior horns of the spinal cord and close to them in structure. Regulates the work of the muscles of the shoulder girdle. XII pair - hypoglossal nerve(n. hypoglossus) - motor. The nucleus is located in the sublingual triangle of the rhomboid fossa. On its neurons ends part of the fibers of the cortical-nuclear tract, as well as the axons of the neurons of the sensory nuclei of the trigeminal and vagus nerves. Functionally, the core is associated with the coordination of tongue movements during chewing. The presence of cortical inputs ensures the voluntary movement of the tongue during speech.

The last group of nuclei is nuclei of the reticular formation. Large nuclei located within the medulla oblongata act as centers of such complex reflex acts as breathing, heartbeat, vascular tone, etc. Distinctive features of the reticular centers are weak differentiation, the absence of clear boundaries, a large number of inputs and projections to various brain structures. They are located in the central parts of the medulla oblongata. Within the medulla oblongata are located vital centers of respiration and circulation. Therefore, if the medulla oblongata is damaged, death can occur.

Fig.5. Projection of the nuclei of the cranial nerves on the rhomboid fossa.

1 - the nucleus of the oculomotor nerve; 2 - the nucleus of the trochlear nerve; 3 - the motor nucleus of the trigeminal nerve; 4 - sensitive nucleus of the trigeminal nerve; 5 - the motor nucleus of the glossopharyngeal nerve; 6 - the motor nucleus of the vagus nerve; 7 - the nucleus of the efferent nerve; 8 - the motor nucleus of the facial nerve; 9 - the core of the accessory nerve; 10, 11 - nuclei of the vestibulo-cochlear nerve; 12 - sensitive nucleus of the vagus nerve; 13 - sensitive nucleus of the glossopharyngeal nerve; 14 - the nucleus of the hypoglossal nerve; 15,16,17 - cerebellar peduncles; 18 - facial mound; 19 - brain strips

white matter the medulla oblongata is represented mainly by longitudinally running nerve fibers. Many of them are transit, i.e. pass without switching. Ascending fibers follow from the spinal cord. This is - thin and wedge-shaped bundles, which, having switched in the nuclei of the same name, form bulbothalamic and bulbocerebellar tracts. On the lateral surface of the medulla oblongata pass anterior and posterior dorsal tracts. The first continues into the bridge, the second, as part of the lower cerebellar peduncle, enters the cerebellum. Medial transit passes dorsal thalamic tract, formed by the fibers of the anterior and lateral tracts of the same name of the spinal cord. Descending fibers are represented by bundles coming from various motor nuclei of the brain. The largest is pyramidal tract, running along the ventral surface of the medulla oblongata, its fibers will form lateral and anterior corticospinal tracts. Dorsal of the pyramids passes reticulospinal tract, and laterally vestibulospinal. Near the dorsal surface of the medulla oblongata pass posterior and medial longitudinal bundles. Ahead of them is tectospinal tract. Passes mediolaterally red nuclear-spinal tract. In addition, paths are formed in the medulla oblongata connecting its sensitive nuclei with the overlying centers of the brain - nuclear-thalamic and nuclear-cerebellar pathways. The first one transmits general information from the receptors of the head and receptors of internal organs. According to the second - unconscious proprioceptive impulses from the head region. On the neurons of the motor nuclei of the cranial nerves of the medulla oblongata end fibers of the corticonuclear tract.

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human medulla oblongata

Medulla is located in the lower half of the brain stem and connects to the spinal cord, being, as it were, its continuation. It is the posterior part of the brain. The shape of the medulla oblongata resembles an onion or cone. At the same time, its thick part is directed upward to the hindbrain, and the narrow part is directed downward to the spinal cord. The longitudinal length of the medulla oblongata is approximately 30-32 mm, its transverse size is about 15 mm, and the anteroposterior size is about 10 mm.

The place where the first pair of cervical nerve roots exits is considered the border of the spinal cord and medulla oblongata. The bulbar-pontine groove on the ventral side is the upper border of the medulla oblongata.

Medulla oblongata: fundamentals of structure and functioning

The striae (auditory grooves of the medulla oblongata) represent the upper border of the medulla oblongata from the dorsal side. The medulla oblongata is limited from the spinal cord on the ventral side by the crosshairs of the pyramids. There is no clear border of the medulla oblongata on the dorsal side, and the place where the spinal roots exit is considered to be the border. At the border of the medulla oblongata and the pons, there is a transverse groove that delimits these two structures together with the medullary stripes.

On the outer ventral side of the medulla oblongata there are pyramids in which the corticospinal tract passes and olives containing the nuclei of the lower olive, which are responsible for balance.

On the dorsal side of the medulla oblongata there are wedge-shaped and thin bundles that end in tubercles of the wedge-shaped and thin nuclei. Also on the dorsal side is the lower part of the rhomboid fossa, which is the bottom of the fourth ventricle and the lower cerebellar peduncles. The posterior choroid plexus is located there.

Contains many nuclei that are involved in a variety of motor and sensory functions. In the medulla there are centers responsible for the work of the heart (heart center), respiratory center. Through this part of the brain, vomiting and vasomotor reflexes are controlled, as well as autonomic functions of the body, such as breathing, coughing, blood pressure, and the frequency of contractions of the heart muscle.

The formation of Rh8-Rh4 rhombomeres occurs in the medulla oblongata.

Ascending as well as descending paths in the medulla oblongata go from the left to the right side and inherit from the right.

The medulla oblongata includes:

glossopharyngeal nerve
part of the fourth ventricle
accessory nerve
nervus vagus
hypoglossal nerve
part of vestibulocochlear nerve

Lesions and injuries of the medulla oblongata are usually always fatal due to its location.

Functions performed

The medulla oblongata is responsible for certain functions of the autonomic nervous system, such as:

Breathing by controlling the level of oxygen in the blood by sending signals to the intercostal muscles, increasing the speed of their contraction to saturate the blood with oxygen.
reflex functions. These include sneezing, coughing, swallowing, chewing, vomiting.
Heart activity. Through sympathetic excitation, cardiac activity increases, and parasympathetic inhibition of cardiac activity also occurs. In addition, blood pressure is controlled by vasodilation and vasoconstriction.

Features of the functional organization. The human medulla oblongata is about 25 mm long. It is a continuation of the spinal cord. Structurally, in terms of the variety and structure of the nuclei, the medulla oblongata is more complex than the spinal cord. Unlike the spinal cord, it does not have a metameric, repeatable structure; the gray matter in it is located not in the center, but with nuclei to the periphery.

In the medulla oblongata there are olives associated with the spinal cord, the extrapyramidal system and the cerebellum - this is a thin and wedge-shaped nucleus of proprioceptive sensitivity (the nucleus of Gaulle and Burdach). Here are the intersections of the descending pyramidal pathways and ascending pathways formed by thin and wedge-shaped bundles (Gaulle and Burdach), the reticular formation.

The medulla oblongata, due to its nuclear formations and the reticular formation, is involved in the implementation of autonomic, somatic, gustatory, auditory, and vestibular reflexes. A feature of the medulla oblongata is that its nuclei, being excited sequentially, ensure the implementation of complex reflexes that require the sequential inclusion of different muscle groups, which is observed, for example, when swallowing.

The nuclei of the following cranial nerves are located in the medulla oblongata:

a pair of VIII cranial nerves - the vestibulocochlear nerve consists of the cochlear and vestibular parts. The cochlear nucleus lies in the medulla oblongata;

pair IX - glossopharyngeal nerve (p.

Medulla oblongata: anatomy, structure of nuclei and functions

glossopharyngeus); its core is formed by 3 parts - motor, sensory and vegetative. The motor part is involved in the innervation of the muscles of the pharynx and oral cavity, the sensitive part receives information from the taste receptors of the posterior third of the tongue; autonomic innervates the salivary glands;

pair X - the vagus nerve (n.vagus) has 3 nuclei: the autonomic innervates the larynx, esophagus, heart, stomach, intestines, digestive glands; sensitive receives information from the receptors of the alveoli of the lungs and other internal organs, and motor (the so-called mutual) provides a sequence of contraction of the muscles of the pharynx, larynx when swallowing;

pair XI - accessory nerve (n.accessorius); its nucleus is partially located in the medulla oblongata;

pair XII - hypoglossal nerve (n.hypoglossus) is the motor nerve of the tongue, its core is mostly located in the medulla oblongata.

Touch functions. The medulla oblongata regulates a number of sensory functions: the reception of skin sensitivity of the face - in the sensory nucleus of the trigeminal nerve; primary analysis of taste reception - in the nucleus of the glossopharyngeal nerve; reception of auditory stimuli - in the nucleus of the cochlear nerve; reception of vestibular stimuli - in the upper vestibular nucleus. In the posterior superior sections of the medulla oblongata, there are paths of skin, deep, visceral sensitivity, some of which switch here to the second neuron (thin and sphenoid nuclei). At the level of the medulla oblongata, the enumerated sensory functions implement the primary analysis of the strength and quality of stimulation, then the processed information is transmitted to the subcortical structures to determine the biological significance of this stimulation.

reflex functions. Numerous reflexes of the medulla oblongata are divided into vital and non-vital, but such a representation is rather arbitrary. The respiratory and vasomotor centers of the medulla oblongata can be attributed to vital centers, since a number of cardiac and respiratory reflexes are closed in them.

The medulla oblongata organizes and implements a number of protective reflexes: vomiting, sneezing, coughing, tearing, closing of the eyelids. These reflexes are realized due to the fact that information about irritation of the receptors of the mucous membrane of the eye, oral cavity, larynx, nasopharynx through the sensitive branches of the trigeminal and glossopharyngeal nerves enters the nuclei of the medulla oblongata, from here comes the command to the motor nuclei of the trigeminal, vagus, facial, glossopharyngeal, accessory or hypoglossal nerves, as a result, one or another protective reflex is realized. In the same way, due to the sequential inclusion of muscle groups of the head, neck, chest and diaphragm, reflexes of eating behavior are organized: sucking, chewing, swallowing.

Static reflexes Statokinetic reflexes

Most of the autonomic reflexes of the medulla oblongata are realized through the nucleus of the vagus nerve which receive information about the state of activity of the heart, blood vessels, digestive tract, lungs, digestive glands, etc. In response to this information, the nuclei organize the motor and secretory reactions of these organs.

The activity of the nuclei of the vagus nerve is also manifested in increased secretion of the bronchial, gastric, intestinal glands, in the excitation of the pancreas, secretory cells of the liver.

Located in the medulla oblongata salivation center, the parasympathetic part of which provides an increase in general secretion, and the sympathetic part - protein secretion of the salivary glands.

The respiratory and vasomotor centers are located in the structure of the reticular formation of the medulla oblongata. The peculiarity of these centers is that their neurons are able to be excited reflexively and under the influence of chemical stimuli.

respiratory center localized in the medial part of the reticular formation of each symmetrical half of the medulla oblongata and is divided into two parts, inhalation and exhalation.

In the reticular formation of the medulla oblongata, another vital center is represented - vasomotor center(regulation of vascular tone). It functions in conjunction with the overlying structures of the brain and, above all, with the hypothalamus. Excitation of the vasomotor center always changes the rhythm of breathing, the tone of the bronchi, intestinal muscles, bladder, ciliary muscle, etc. This is due to the fact that the reticular formation of the medulla oblongata has synaptic connections with the hypothalamus and other centers.

In the middle sections of the reticular formation there are neurons that form the reticulospinal pathway, which has an inhibitory effect on the motor neurons of the spinal cord. At the bottom of the IV ventricle, the neurons of the "blue spot" are located. Their mediator is norepinephrine. These neurons cause activation of the reticulospinal pathway during REM sleep, which leads to inhibition of spinal reflexes and a decrease in muscle tone.

Damage symptoms. Damage to the left or right half of the medulla oblongata above the intersection of the ascending pathways of proprioceptive sensitivity causes disturbances in the sensitivity and work of the muscles of the face and head on the side of the injury. At the same time, on the opposite side relative to the side of the injury, there are violations of skin sensitivity and motor paralysis of the trunk and limbs. This is explained by the fact that the ascending and descending pathways from the spinal cord and into the spinal cord intersect, and the nuclei of the cranial nerves innervate their half of the head, i.e., the cranial nerves do not intersect.

21. Static (reflexes of position, straightening) and statokinetic reflexes, the mechanism of formation, their significance.

In addition, the medulla oblongata organizes postural reflexes. These reflexes are formed by afferentation from the receptors of the vestibule of the cochlea and the semicircular canals to the superior vestibular nucleus; from here, the processed information for assessing the need for a change in posture is sent to the lateral and medial vestibular nuclei. These nuclei are involved in determining which muscle systems, segments of the spinal cord should take part in a change in posture, therefore, from the neurons of the medial and lateral nuclei, along the vestibulospinal pathway, the signal arrives at the anterior horns of the corresponding segments of the spinal cord, innervating the muscles, whose participation in changing the posture in necessary at the moment.

Posture change is carried out due to static and statokinetic reflexes. Static reflexes regulate the tone of skeletal muscles in order to maintain a certain position of the body. Statokinetic reflexes medulla oblongata provide a redistribution of the tone of the muscles of the body to organize a posture corresponding to the moment of rectilinear or rotational movement.

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Blood supply to the brain

Malformations of the brain

brain tumors

The brain is the anterior part of the central nervous system, located in the cranial cavity. It consists of the hemispheres and the brain stem with the cerebellum.

Anatomy
The brain is divided into five sections: 1) medulla oblongata (myelencephalon, or medulla oblongata); 2) the hindbrain (metencephalon), consisting of the bridge (varoli) and the cerebellum; 3) the midbrain (mesencephalon), in which the legs of the brain and the quadrigemina are located; 4) the diencephalon (diencephalon), consisting of the visual hillock (thalamus), epithelium, hypothalamus and foreign tuberosity; 5) telencephalon (telencephalon), or large hemispheres.

Just as in the spinal cord (see), gray and white matter are distinguished in the brain. From the gray matter - accumulations of nerve cells - in the brain, the nuclei and the cortex of the cerebral hemispheres and the cerebellum are formed. White matter is bundles of long and short nerve fibers that connect various formations of the brain with the spinal cord. In the brain stem there are clusters of nerve cells with numerous short fibers - a mesh formation (formatio reticularis).

Medulla is a direct continuation of the spinal cord. Important cranial nerves (glossopharyngeal, vagus, accessory, and hypoglossal) originate in the nuclei of the medulla oblongata. Through it pass the paths that conduct impulses from the spinal cord to the brain (centripetal) and from the brain to the spinal cord (centrifugal). One important pathway is the pyramidal pathway, which connects the motor cortex with the motor cells of the anterior horns of the spinal cord. At the border of the medulla oblongata and spinal cord, the pyramidal pathways cross, which causes functional disorders in case of damage to one or another area of the brain. At defeat of a pyramidal beam above a crossover the hemiplegia develops (see) on the opposite side of a body; if the cranial nerves are simultaneously affected, then their function is impaired on the side of the body that is the same name as the lesion (see Alternating syndromes).

The pons of the brain also contains the nuclei of the cranial nerves - trigeminal, abducens, facial and stato-acoustic (vestibulocochlear).

Through the medulla oblongata and the bridge, the regulation of blood pressure and respiration and such reflexes as chewing, swallowing, vomiting, coughing, sneezing, blinking are carried out.

The junction of the pons, medulla oblongata and cerebellum is called the pontocerebellar angle. It is located at the base of the brain in the posterior cranial fossa. In this area, the facial and stato-acoustic nerves exit to the surface of the brain. With tumors in the region of the cerebellopontine angle, the nearest sections of the medulla oblongata, pons and cerebellum are compressed and the corresponding clinical symptoms develop.

Part midbrain includes the quadrigemina and the legs of the brain. The quadrigemina is located on the dorsal surface of the midbrain. The anterior tubercles of the quadrigemina are the primary visual centers, and the posterior tubercles are auditory. In the legs of the brain there are a red nucleus and a black substance, which take part in the regulation of the plastic tone of the muscles of the body, and at the bottom of the cerebral (Sylvian) aqueduct - the nuclei of the oculomotor and trochlear cranial nerves. Through the legs of the brain, ascending paths pass, carrying impulses to the thalamus and large hemispheres, and descending paths, conducting impulses to the medulla oblongata and spinal cord. The midbrain also contains the reticular substance (see above).

Main formations diencephalon- visual hillocks, which are the collector of all sensory pathways (except olfactory), passing to the large brain, hypothalamus (see. Hypothalamus), geniculate bodies with subcortical visual and auditory centers and the pineal body with adjacent formations.

In each part of the brain there are cavities - the ventricles of the brain.

Ascending upward, the central canal of the spinal cord, expanding, passes into the IV ventricle, the bottom of which is a rhomboid fossa formed by the medulla oblongata and the bridge. In the thickness of the bottom of the IV ventricle are the nuclei of the cranial nerves (from V to XII pairs). Above the IV ventricle is the cerebellum (see). Outside, the IV ventricle is limited by the legs of the cerebellum, from above - by the vascular plate, the upper and lower medullary velum. Above, the IV ventricle narrows and in the region of the midbrain passes into the cerebral (Sylvian) aqueduct, surrounded by gray matter. The cerebral aqueduct at the top passes into the third ventricle - the cavity of the diencephalon. The lateral walls of the third ventricle are visual tubercles; the upper one is the epithelial plate (roof of the third ventricle), above which lies the fornix and corpus callosum of the cerebral hemispheres; anterior - anterior commissure and arch columns. Between the columns of the fornix and the anterior corpus callosum is a transparent septum. The bottom of the third ventricle is the hypothalamus: the end plate, the optic chiasm, the infundibulum, the pituitary gland, the gray tubercle, and the mammillary bodies.

The cavity of the third ventricle is connected through the interventricular openings with the lateral ventricles of the cerebral hemispheres. In the lateral ventricles, the anterior, posterior, and inferior horns of the lateral ventricles are distinguished. Just like in the IV and III ventricles, they contain choroid plexuses.

The choroid plexuses produce cerebrospinal fluid (see), which fills the ventricles of the brain and the cavity of the central spinal canal. Through the holes of the lower cerebral sail, cerebrospinal fluid enters the cavity of the IV ventricle into the subarachnoid space (see Meninges) and also washes the outer surface of the brain and spinal cord. If the patency of these holes is disturbed, as well as when the cerebral aqueduct is compressed by a tumor, occlusive hydrocephalus may develop (see).

telencephalon is divided by a longitudinal groove into two hemispheres, interconnected by the corpus callosum, fornix and anterior commissure. The corpus callosum is a powerful bundle of fibers connecting the hemispheres of the brain. The arch is divided anteriorly into columns, and posteriorly into legs. Between the legs of the vault lies the commissure of the vault. The columns of the fornix are sent to the mammillary bodies, from the inner core of which a bundle originates, going to the thalamus. The cerebral hemispheres are divided into the frontal, parietal, temporal, occipital lobes and the insula. The surface of the cerebral hemisphere - the cloak (pallium) - is indented with furrows, between which lie convolutions. The deepest lateral (Sylvian) groove separates the temporal lobe from the frontal and parietal. An island is located in the depth of the lateral groove. The part of the frontal and parietal lobes above the lateral sulcus is called the central tegmentum. The frontal and parietal lobes are separated from each other by the central (Roland) groove. Surrounding the central sulcus are the precentral and postcentral gyrus. In the frontal lobe there are two or three frontal grooves, its lower surface is cut through by the orbital and olfactory grooves. On the latter lies the olfactory tract.

The parietal lobe is divided into lower and upper lobules, it is cut through by the interparietal sulcus. On the inner surface of the occipital lobe are spur and parietal-occipital grooves. Between them is the so-called wedge. The sulcus of the corpus callosum and the cingulate sulcus run along the inner surface of the hemisphere; between them lies the cingulate gyrus, which is part of the limbic region.

Under the gray matter of the hemispheres - the cerebral cortex - lie the white matter and the basal ganglia. The white matter, consisting of fibers, forms the outer and inner bags.

In the cortex of the telencephalon there is a representation of various functions (cortical centers). According to the teachings of I.P.

Medulla oblongata, structure, functions and development

Pavlov, the cortex is the cortical end of the analyzers. The visual analyzer is represented in the occipital region, the auditory analyzer in the temporal region, general sensitivity in the postcentral region, and the motor analyzer in the precentral region.

The limbic area is related to autonomic functions. Areas such as the frontal, lower parietal, temporal-parietal-occipital subregion belong to the interanalyzer zones that perform higher mental, speech functions, as well as subtle purposeful hand movements.

Rice. 1. Sagittal section of the brain: 1 - frontal lobe of the hemisphere; 2- cingulate gyrus; 3 - corpus callosum; 4 - transparent partition; 5 - vault; 6 - anterior commissure; 7 - optic chiasm; 8 - pituitary gland; 9 - temporal lobe of the hemisphere; 10 - bridge; 11 - medulla oblongata; 12 - cerebellum; 13 - fourth ventricle; 14 - occipital lobe of the hemisphere; 15 - parietal lobe of the hemisphere; 16 - quadrigemina; 17 - pineal body; 18 - cerebral water supply; 19 - visual tubercle; 20 - hypotuberous region.

Rice. 2. Brain. Side view: 1- frontal lobe; 2 - temporal lobe; 3 - medulla oblongata; 4 - cerebellum; 5 - occipital lobe; b - parietal lobe; 7 - lateral furrow; 8 - central furrow.

Rice. 3. Brain. Top view: 1 - frontal lobes of the hemispheres; 2 - parietal lobes of the hemispheres; 3 - occipital lobes of the hemispheres; 4 - longitudinal fissure of the brain.

Rice. 4. The brain stem. Top view: 1-visual tubercle; 2 - pineal body; 3 - quadrigemina; 4 - block nerve; 5 - trigeminal nerve; 6 - upper brain sail; 7-superior cerebellar peduncle; 8 - middle cerebellar peduncle; 9 - facial nerve; 10 - diamond-shaped fossa; 11 - glossopharyngeal nerve; 12 - vagus nerve; 13 - accessory nerve; 14 - medulla oblongata; 15 - lower leg of the cerebellum; 16 - leg of the brain.

Rice. 5. Base of the brain: 1 - frontal lobes of the hemisphere; 2 - olfactory tract; 3 - optic nerve; 4 - temporal lobe of the hemisphere; 5 - oculomotor nerve; 6 - block nerve; 7 - bridge; 8 - trigeminal nerve; 9 - abducens nerve; 10 - facial and vestibulocochlear nerves; 11 - glossopharyngeal nerve; 12 - vagus nerve; 13 - accessory nerve; 14 - cerebellum; 15 - occipital lobes of the hemisphere; 16 - pyramids of the medulla oblongata; 17 - hypoglossal nerve; 18 - mastoid body; 19 - gray mound and funnel; 20 - optic chiasm.

Lecture Search

Lecture No. 18-20 “Functional anatomy of the brain. CHMN."

1. Structural organization of the brain, its physiological role.

2. Medulla oblongata - structural features, physiological role.

3. Hind brain - structural features, physiological role.

4. Midbrain - structural features, physiological role.

5. Diencephalon - structural features, physiological role.

6. FMN-area and the nature of innervation.

7. Anatomical and physiological features of the cerebral cortex.

8. Liquor formation, composition, functions.

Structural organization of the brain, its physiological role.

The brain is the main regulator of all the functions of a living organism. It is one of the elements of the central nervous system. The human brain consists of 25 billion neurons. These cells are the gray matter. Inside the brain there are cavities called ventricles. Paired cranial nerves (12 pairs) depart from it in different parts of the body.

In the course of evolution, a strong cranium has formed around the human brain, protecting this organ. The brain occupies more than 90% of the space of the skull. It consists of three main parts:

large hemispheres;

the brain stem

cerebellum.

It is also customary to distinguish five parts of the brain:

forebrain (large hemispheres);

hindbrain (cerebellum, pons Varolii);

·medulla;

the midbrain;

diencephalon.

The first section located above the spinal cord is medulla, it is actually its continuation.

The medulla oblongata: its structure, nuclei and functions

The medulla oblongata is composed of gray and white matter.
Next comes Pons- This is a roller of nerve transverse fibers and gray matter. The main artery that feeds the brain passes through it. It starts above the medulla oblongata and passes into the cerebellum.
Cerebellum consists of two hemispheres and a worm, as well as white matter and gray matter covering it. This department is connected by pairs of "legs" to the medulla oblongata and midbrain.
midbrain consists of two visual hillocks, and two auditory (quadrigemina). Nerve fibers that connect the brain with the spinal cord depart from these tubercles.
Large hemispheres of the brain separated by a deep fissure with the corpus callosum inside, which connects these two sections of the brain. Each hemisphere has the following areas:

temporal,

Parietal and

Occipital.

The hemispheres are covered by the cerebral cortex.
In addition, there are three layers of the brain:

hard, which is the periosteum of the inner surface of the skull; a large number of pain receptors are concentrated in this shell;

arachnoid, which is closely adjacent to the cerebral cortex, but does not line the gyrus; the space between it and the hard shell is filled with a serous fluid, and the space between it and the cerebral cortex is filled with cerebrospinal fluid;

soft, consisting of a system of blood vessels and connective tissue, in contact with the entire surface of the substance of the brain, and nourishing it.

Medulla oblongata - structural features, physiological role.

The medulla oblongata is a direct continuation of the spinal cord. Its lower border is considered to be the exit point of the roots of the I cervical spinal nerve, the upper one is the posterior edge of the bridge. The length of the medulla oblongata is about 25 mm, the shape approaches a truncated cone, the base facing up. The anterior surface is divided by the anterior median fissure, on the sides of which are elevations - pyramids formed by bundles of nerve fibers of the pyramidal pathways. These fibers partially cross (cross pyramids) in the depth of the described fissure on the border with the spinal cord. To the side of the pyramid on each side is an olive about 1.5 cm long, containing the nuclei of gray matter. The medulla oblongata is built of white and gray matter, the latter is represented by the nuclei of the IX-XII pairs of cranial nerves, olives, the reticular formation, centers of respiration and blood circulation. White matter should be distinguished from gray matter, which is formed by long and short fibers that make up the corresponding pathways.

The medulla oblongata regulates the sensory functions: skin sensitivity of the face - in the sensory nucleus of the trigeminal nerve; primary analysis of taste - in the nucleus of the glossopharyngeal nerve; auditory irritations - in the nucleus of the cochlear nerve; vestibular irritations - in the upper vestibular nucleus. At the level of the medulla oblongata, the listed sensory functions undergo a primary analysis of the strength and quality of stimulation, then the processed information is transmitted to subcortical structures to determine the biological significance of this stimulation.

It should be noted that the medulla oblongata organizes and implements a number of protective reflexes: vomiting, sneezing, coughing, tearing, closing of the eyelids. These reflexes are realized due to the fact that information about irritation of the receptors of the mucous membrane of the eye, oral cavity, larynx, nasopharynx through the sensitive branches of the trigeminal and glossopharyngeal nerves enters the nuclei of the medulla oblongata, from here comes the command to the motor nuclei of the trigeminal, vagus, facial, glossopharyngeal, accessory or hypoglossal nerves, as a result, one or another protective reflex is realized. In the same way, due to the sequential inclusion of muscle groups of the head, neck, chest and diaphragm, reflexes of eating behavior are organized: sucking, chewing, swallowing.

Excitation of the nuclei of the vagus nerve causes an increase in the contraction of the smooth muscles of the stomach, intestines, gallbladder and, at the same time, relaxation of the sphincters of these organs. At the same time, the work of the heart slows down and weakens, the lumen of the bronchi narrows. The activity of the nuclei of the vagus nerve is also manifested in increased secretion of the bronchial, gastric, intestinal glands, in the excitation of the pancreas, secretory cells of the liver.

The main centers of the medulla oblongata:

- salivation center, the parasympathetic part of which provides an increase in general secretion, and the sympathetic part - protein secretion of the salivary glands;

- respiratory center is localized in the medial part of the reticular formation of each symmetrical half of the medulla oblongata and is divided into two parts - inhalation and exhalation.

- vasomotor center(regulation of vascular tone) - this vital center is also localized in the reticular formation of the medulla oblongata; it functions in conjunction with the overlying structures of the brain and, above all, with the hypothalamus. Excitation of the vasomotor center always changes the rhythm of breathing, the tone of the bronchi, the muscles of the intestines, the bladder, etc. This is due to the fact that the reticular formation of the medulla oblongata has synaptic connections with the hypothalamus and other centers.

The brain is the most important organ that regulates absolutely all aspects of human life. It has a rather complex anatomical structure. One of its significant departments is the medulla oblongata, the structure and functions of which will be discussed in detail in our article.

In contact with

Classmates

They are divided into several groups:

Protective - hiccups, sneezing, coughing, vomiting, etc.
Cardiac and vascular reflexes.
Regulating the vestibular apparatus.
Digestive.
Reflexes of ventilation of the lungs.
Adjusting reflexes responsible for maintaining posture and muscle tone.

Anatomy

This part of the central nervous system directly involved in information processing, which comes to him from all the receptors of the human body.

The nuclei of five pairs of cranial nerves are located in this part of the nervous system. They are grouped in the caudal region below the floor of the 4th ventricle:

Conducting paths

Pass through the medulla oblongata several conductive sensory pathways from the spinal region to the overlying parts of the central nervous system:

Thin.
wedge-shaped.
Spinothalamic.
Spinocerebellar.

The localization of these pathways in the medulla oblongata and spinal cord is identical.

In the lateral white matter are located efferent pathways:

Rubrospinal.
Olivospinal.
Tectospinal.
Reticulospinal.
Vestibulospinal.

In the ventral part are the fibers of the corticospinal motor pathway. Its fibers in the medulla oblongata are formed into special formations, which are called pyramids. At the level of the pyramids, 80% of the fibers of the descending pathways form a cross between them. The remaining 20% of the fibers form a decussation and pass to the opposite side below - at the level of the spinal cord.

Main functions

There are a large number of tasks that the medulla oblongata is designed to solve. Functions of this part of the nervous system are divided into the following groups:

Touch.
Reflex.
Integrative.
Conductor.

Below they will be considered in more detail.

Touch

This kind of function is in the acceptance by neurons of signals from sensory receptors in response to environmental influences or changes in the internal environment of the body. These receptors are formed from sensory epithelial cells or from the nerve endings of sensory neurons. The bodies of sensory neurons are located in the peripheral nodes or in the brainstem itself.

In the neurons of the brain stem, the analysis of signals sent by the respiratory system takes place. This may be a change in the gas composition of the blood or stretching of the pulmonary alveoli. According to these indicators, not only hemodynamics is analyzed, but also the state of metabolic processes. In addition, the activity of the respiratory system is analyzed in the nuclei. Based on the results of such an assessment, there is a reflex regulation of the functions of respiration, blood circulation, and the digestive system.

In addition to internal signals, the centers of the medulla oblongata regulate and process signals about changes in the external environment- from temperature receptors, taste, auditory, tactile or pain.

From the centers, the signals are sent along the conductive fibers to the brain regions located above. There, a more subtle analysis and identification of these signals is carried out. As a result of processing these data, certain emotional-volitional and behavioral reactions are formed in the cerebral cortex. Some of them are carried out in the same way with the help of the structures of the medulla oblongata. In particular, a decrease in the content of oxygen in the blood and the accumulation of carbon dioxide can lead to the development of unpleasant sensations and a negative emotional state in a person. As a behavioral therapy, a person begins to seek access to fresh air.

Conductor

Conduction functions consist in the fact that nerve impulses are conducted from sensory components through this area to other parts of the nervous system.

Nerve impulses of an afferent nature come to the centers from sensory receptors located:

All these impulses are carried along the fibers of the cranial nerves to the corresponding nuclei, where they are analyzed and, in response to stimuli, an appropriate reflex reaction is formed. From the centers of this department, efferent nerve impulses can be sent to other parts of the trunk or cortex in order to carry out more complex behavioral reactions in response to stimuli.

Integrative

This type of function may appear in the formation of complex reactions, which cannot be limited to the framework of the simplest reflex actions. Neurons carry information about some regulatory processes, the implementation of which requires joint participation with other parts of the nervous system, including the cerebral cortex. The algorithm of such complex actions is programmed in the neurons of this part of the brain.

An example of such an effect can be a compensatory change in the position of the eyeballs during a change in the position of the head - nodding, rocking, etc. In this case, there is a well-coordinated interaction of the nuclei of the oculomotor nerves and the vestibular apparatus with the participation of the components of the medial longitudinal bundle.

Some of the neurons of the mesh structure have autonomy and automatism of functions. Its task is to coordinate the nerve centers in various parts of the central nervous system and their toning.

reflex

The most important reflex functions are - this is the regulation of skeletal muscle tone and the preservation of posture in space. In addition, the reflex functions include the protective actions of the body, as well as the organization and maintenance of the balance of the respiratory system and blood circulation.

Medulla, medulla oblongdta ( myelencephalon ), located between the hindbrain and spinal cord.

Anatomy and topography of the medulla oblongata.

The upper border on the ventral surface of the brain runs along the lower edge of the pons, on the dorsal surface it corresponds to the cerebral stripes of the fourth ventricle. The boundary between the medulla oblongata and the spinal cord corresponds to the level of the foramen magnum.

In the medulla oblongata, ventral, dorsal and two lateral surfaces are distinguished which are separated by furrows.

Furrows of the medulla oblongata

are a continuation of the furrows of the spinal cord and have the same names: anterior median fissure,fissura mediana ventrdlls; posterior median sulcus,sulcus medidnus dorsalis; anterolateral furrow,sulcus ventrolaterlis; posterolateral furrow,sulcus dorsolaterdlis.

On the ventral surface medulla oblongata are located pyramids,pyramides.

In the lower part of the medulla oblongata, the bundles of fibers that make up the pyramids enter the lateral cords of the spinal cord. This transition of fibers is called cross pyramids,decussatioRUramidum. The place of decussation also serves as an anatomical boundary between the medulla oblongata and the spinal cord. To the side of each pyramid of the medulla oblongata is olive,olive. In this groove, the roots of the hypoglossal nerve (XII pair) emerge from the medulla oblongata.

On the dorsal surface ends with a thin and wedge-shaped bundles of the posterior cords of the spinal cord.

thin beam

, fasciculus grdcilis, forms tubercle of the thin nucleus,tuberculum grdcile.

wedge-shaped bundle

, fasciculus cuneatus, forms tubercle of the sphenoid nucleus,tuber culum cunetum.

Dorsal to the olive from the posterolateral sulcus of the medulla oblongata - retro-olive furrow,sulcus retro— olivdris, out the roots of the glossopharyngeal, vagus and accessory nerves (IX, X and XI pairs).

Fibers extending from the sphenoid and tender nuclei join the dorsal part of the lateral funiculus. Together they form the inferior cerebellar peduncle. The surface of the medulla oblongata, bounded from below and laterally by the inferior cerebellar peduncles, is involved in the formation of the rhomboid fossa, which is the bottom of the IV ventricle.

In the lower regions are right and left lower olive kernels,nuclei olivares cauddles.

Slightly above the lower olive cores is located reticular formation,formdtio reticuldris. Between the lower olive cores there is an inter-olive layer, represented by internal arcuate fibersfibrae arcuatae internae, - offshoots. These fibers form medial loop,lemniscus medialis. The fibers of the medial loop belong to the proprioceptive pathway of the cortical direction and form in the medulla oblongata decussation of medial loops,decussdtio lem— niscorum medidlum. Somewhat ventrally, the fibers of the anterior spinal-cerebellar and red-nuclear-spinal tracts pass. Above the intersection of the medial loops is the posterior longitudinal bundle, fasciculus longitudinalis dorsdlis.

The position of the nuclei and pathways in the medulla oblongata.

Nuclei are located in the medulla oblongata IX, X, XI and XII pairs of cranial nerves.

The ventral parts of the medulla oblongata are represented by descending motor pyramidal fibers. Dorso-laterally, ascending pathways pass through the medulla oblongata, connecting the spinal cord with the cerebral hemispheres, the brain stem, and the cerebellum.

Medulla oblongata (myelencephalon, bulbus) , - a derivative of the rhomboid brain, which at the stage of five bubbles is divided into the hindbrain, metencephalon , and the medulla oblongata, myelencephalon.

Topography of the medulla oblongata.

Being part of the brain stem, it is a continuation of the spinal cord in the form of its thickening.

The medulla oblongata has cone shape , somewhat compressed in the posterior sections and rounded in the anterior. Its narrow end is directed downwards to the spinal cord, the upper, expanded, to the bridge and the cerebellum.

The boundary between the medulla oblongata and the spinal cord is considered to be the exit point of the superior radicular thread of the first cervical nerve or the lower level of the pyramidal decussation. The medulla oblongata is separated from the pons by a transverse bulbar pontine groove, well expressed on the anterior surface, from which the abducens nerve emerges on the surface of the brain.

The longitudinal size of the medulla oblongata is 3.0–3.2 cm, the transverse size is up to 1.5 cm on average, and the anteroposterior size is up to 1 cm.

medulla oblongata, bridge, pons, and peduncles of the brain, pedunculi cerebri;

front view.

The anterior (ventral) surface of the medulla oblongata is located on the clivus and occupies its lower section up to the foramen magnum. It runs through the anterior median fissure, fissura mediana ventralis (anterior), which is a continuation of the eponymous fissure of the spinal cord.

At the level of the exit of the radicular filaments of the I pair of cervical nerves, the anterior median fissure is somewhat interrupted, becomes less deep due to the pyramidal decussation formed here (motor decussation), decussatio pyramidum(decussatio motoria).

In the upper sections of the anterior surface of the medulla oblongata, on each side of the anterior median fissure, there is a cone-shaped roller - a pyramid (medulla oblongata), pyramis (medullae oblongatae).

On transverse sections of the medulla oblongata, it can be determined that each pyramid is a complex of bundles (they are visible if the edges of the anterior median fissure are stretched to the sides), which partially intersect each other. Next, the fibers pass into the system of the lateral funiculus of the spinal cord, where they follow as lateral corticospinal (pyramidal) tract. The remaining, smaller, part of the bundles, without entering the decussation, follows in the system of the anterior funiculus of the spinal cord as anterior corticospinal (pyramidal) tract. These paths are combined into a single pyramidal path.

Outside of the pyramid is an oblong-rounded elevation - olive, olive. It protrudes on the anterior surface of the lateral funiculus; behind it is limited by a retro-olive furrow, sulcus retroolivaris.

medulla oblongata
oblongata; top view and some
front.

The olive is separated from the pyramid by the anterolateral groove, sulcus ventrolateralis (anterolateralis), which is a continuation of the sulcus of the same name of the spinal cord.

The transition of this groove from the spinal cord to the oblongata is smoothed out by transversely running external arcuate fibers, fibrae arcuatae externae, which, located at the lower edge of the olive, are directed to the pyramid.

Distinguish between anterior and posterior external arcuate fibers, fibrae arcuatae externae ventrales (anteriores) et dorsales (posteriores).

Anterior external arcuate fibers are processes of cells of arcuate nuclei, nuclei arcuati, - accumulations of gray matter adjacent to the anterior and medial surfaces of the pyramid. These fibers come to the surface of the medulla oblongata in the region of the anterior median fissure, go around the pyramid and olive, follow as part of the lower cerebellar peduncle to the cerebellar nuclei.

Posterior outer arcuate fibers formed by processes of cells of the additional sphenoid nucleus, nucleus cuneatus accessorius, and are sent to the cerebellum as part of the lower cerebellar peduncle of its side. The accessory sphenoid nucleus is located dorsolateral to the sphenoid nucleus, nucleus cuneatus. From the depth of the anterolateral groove, 6 to 10 roots of the hypoglossal nerve come to the surface of the medulla oblongata.

On transverse sections through the olives, in addition to nerve fibers, accumulations of gray matter can also be distinguished. The largest of the accumulations is horseshoe-shaped, with a folded surface - this is olive mantle, amiculum olivare, and the core itself is the lower olive core, nucleus olivaria caudalis, in which there is a gate of the lower olive core, hilum nuclei olivaris caudalis (inferioris), for the olivocerebellar tract.

Other nuclei are smaller: one lies inwards - the medial additional olive nucleus, nucleus olivaris accessorius medialis, the other posteriorly is the posterior additional olive core, nucleus olivaris accessorius dorsalis (posterior).

On the dorsal (posterior) surface of the medulla oblongata is the posterior median sulcus, sulcus medianus dorsalis (posterior). Heading up, it reaches a thin cerebral plate - gate valves, obex. The latter, stretched between the tubercles of the thin nucleus, is part of the roof of the IV ventricle in the region of the posterior angle of the rhomboid fossa. Under the valve, the cavity of the central canal of the spinal cord passes into the cavity of the IV ventricle.

Rhomboid fossa, fossa rhomboidea; top and back view.

Two furrows pass outward from the posterior median sulcus: one is closer to the median sulcus - intermediate furrow, another more laterally - posterolateral groove, sulcus dorsolateralis (posterolateralis). From the depths of the latter, 4-5 roots of the glossopharyngeal nerve, 12-16 roots of the vagus nerve and 3-6 cranial roots of the accessory nerve come to the surface of the medulla oblongata.

The posterior median and posterolateral grooves limit the posterior funiculus, funiculus posterior, which is a continuation of the cord of the same name of the spinal cord. The intermediate groove divides the posterior funiculus into two bundles. One bundle lies between it and the posterior median sulcus - this is a thin bundle , fasciculus gracilis, passing at the top into a thickening - a tubercle of a thin nucleus, tuberculum gracile. The second bundle is located between the intermediate and posterolateral grooves - this is a wedge-shaped bundle, fasciculus cuneatus, passing at the top into a less pronounced tubercle of the sphenoid nucleus, tuberculum cuneatum. Each tubercle without sharp boundaries passes into the lower cerebellar peduncle.

In both hillocks there are accumulations of gray matter: in the tubercle of a thin nucleus - a thin nucleus, nucleus gracilis, in the tubercle of the sphenoid nucleus - the sphenoid nucleus, nucleus cuneatus. On the cells of these nuclei, the fibers of the corresponding bundles of the posterior cord end.

On the dorsal surface of the medulla oblongata, between the sphenoid cord and the roots of the accessory nerve, there is an unstable elevation - the trigeminal tubercle, tuberculum trigeminale. It is formed by the caudal division of the nucleus of the spinal tract of the trigeminal nerve.

Immediately at the upper end of the posterolateral groove, above the roots of the glossopharyngeal nerve, in the form of a continuation of the posterior and lateral cords, there is a semicircular thickening - the lower cerebellar peduncle. The structure of each lower cerebellar peduncle, right and left, includes fibers of the conducting systems, which form in it the lateral, large, and medial, smaller, parts.

On transverse sections of the medulla oblongata dorsal to the pyramids, between the olive nuclei, there are fibers that make up the ascending pathways connecting the spinal cord with the brain. reticular formation, formatio reticularis, The medulla oblongata is represented by numerous clusters of neurons and intricately intertwined fibers. It is located mainly in the dorsomedial part of the medulla oblongata and, without a distinct border, passes into the reticular formation of the bridge. In the same zone, the nuclei of the VIII-XII pairs of cranial nerves are located.

The reticular formation of the medulla oblongata also includes a number of cell clusters localized near the nucleus of the hypoglossal nerve and the nucleus of the solitary tract: the posterior paramedian nucleus, nucleus paramedianus dorsalis (posterior); insertion core, nucleus intercalatus, the core of the near-single path, nucleus parasolitarius; commissural core, nucleus comissuralis.

The central core of the substance of the medulla oblongata, formed by clusters of reticular cells and their processes, is referred to as the suture of the medulla oblongata, raphe medullae oblongatae.

Paramedianly located groups of cells of the reticular formation are designated as seam nuclei, nuclei raphae.