The intermediate substance of the spinal cord. Definition and significance of the formation of nuclei of the spinal cord. What is the danger of damage to white and gray matter

Functions and structure

Shells

Vessels

Development

Question 1

functions spinal cord:

1. reflex center all motor reactions of skeletal muscles (except facial), vascular reflexes, genitourinary system, rectum

2. conduction of impulses to and from the brain. The spinal cord is under the control of the brain

3. closure of reflex arcs, transmitting nerve impulse from sensory to motor

4. endocrine- ependymoglia of the spinal canal (intraspinal organ) at a young age produces biologically active substances that regulate blood pressure, circadian rhythms, sexual function

ü development of the spinal cord is directly proportional to the development of skeletal muscles and skin, due to the large receptor field of the skin and a variety of muscle movements

spinal cord (medulla spinalis)

cylindrical cord, compressed dorsoventrally and lies in the spinal canal (occupies 2/3 of the volume)

ü anterior border- large foramen magnum

ü back border- different:

In cattle - up to 4 lumbar vertebrae, in a pig - 6 lumbar, in a dog - 7 lumbar, in a horse - 2 sacral, in a cat - 3 sacral, in humans - up to 2 lumbar

v segment- part of the spinal cord with a pair of nerves

ü allocate cervical, thoracic, lumbar, sacral And tail segments

ü due to the advanced growth of the spinal column, the boundaries of the segments of the spinal cord do not coincide with the boundaries of the vertebrae, the corresponding departments

spinal cord segment

Spinal cord

has 2 extensions:

1) cervical - contains neurons whose processes form the nerves of the thoracic limbs (brachial plexus)

2) lumbosacral - contains neurons, the processes of which form the nerves of the pelvic limbs (lumbar and sacral plexuses). Behind him, the spinal cord narrows - cerebral cone

the cerebral cone continues into terminal(terminal) a thread reaching the 6th tail vertebra

ü terminal thread and tail nerves form ponytail - cauda equina

Surface view

ventral surface:

1. ventral median fissure - lies the spinal central a. and in.

2. two lateral ventral grooves - the exit point of the ventral (motor) roots of the spinal nerves

dorsal surface:

1. shallow dorsal median sulcus

2. dorsal lateral grooves - the place of entry of the dorsal (sensitive) roots of the spinal nerves

Spinal nerves (nervus spinalis)

ü come out in pairs in each segment through the intervertebral foramen

ü each nerve begins with bundles of radicular filaments that form the dorsal (sensory) and ventral (motor) roots

ü on the dorsal roots of thickening - spinal ganglions (ganglia) - from sensitive neurons evicted from the CNS

ü in the cervical and thoracic parts of the spinal cord, the nerves depart perpendicular to the brain, and in the lumbosacral - obliquely back(associated with faster growth of the spine)

Sectional view

Gray matter(substantia grisea) - lies in the center, has the shape butterflies (letters H):

1. dorsal horns(pillars) - sensitive

2. ventral horns - motor

3. lateral horns- in the thoracolumbar and sacral regions

4. intermediate-between dorsal and ventral horns

5. gray spike- connects halves of gray matter

6. spinal canal- in the center of the commissure, cranially passes into the 4th cerebral ventricle of the medulla oblongata, caudally - ends blindly. Expelled by ependymoglia, filled liquor

The structure of the gray matter

ü represented by the bodies of neurons surrounded by glia

ü nucleus of gray matter- a group of neurons of the same structure and function

ü dorsal horn neurons form:

1. gelatinous and spongy substance- axons form their own bundles (intersegmental connections with the participation of many segments in the response)

2. dorsal horn proper nucleus- axons form pathways for pain and temperature sensitivity (lat. dorsal-thalamic path of the opposite side), touch and pressure (vent. dorsal-thalamic path)

3. thoracic nucleus (Clark)- axons form the dorsus. spinal cerebellar tract on own side (coordination of movements)

nuclei and pathways of the spinal cord

types of neurons by localization of axons:

1. radicular- axons are involved in the formation of the ventral (motor) roots of the spinal nerves

2. beam- axons form bundles of white matter that connect segments of the spinal cord with each other and with the brain

3. internal- numerous processes do not come out of the gray matter, connecting the neurons of the nuclei of the spinal cord within the segment

white medulla (substantia alba)- on the periphery of the gray matter of the brain

ü represented by processes of neurons

The horns of gray matter are divided into paired cords: dorsal, ventral, lateral

the cords of opposite sides are connected white spike

ü in the ropes - pathways between segments of the spinal cord, spinal cord and brain:

1) associative - connect segments of the spinal cord at various levels - own beams all cords

2) ascending (sensitive) - to the centers in the brain

3) descending (motor) - from the brain to the neurons of the ventral horns of the spinal cord

cords of the white medulla:

1. dorsal - ascending way, contains 2 bundles:

1) thin (Goll) - from the back of the body and hind limbs

2) wedge-shaped (Burdaha) - from the front of the body and forelimbs

are formed by the axons of the neurons of the spinal ganglions

ü entering the medulla oblongata unite in the medulla-spinal tract (tractus spinobulbaris)

ü conduct impulses from proprioceptors to the medulla oblongata, and then to the cerebral cortex about the position of the body and its parts in space

2. lateral- ascending and descending paths:

ascending:

1) spinal-cerebellar dorsal /Flexiga/ (from the thoracic nucleus)

2) dorsal-cerebellar ventral /Goversa/ (from the intermediate medical nucleus)

3) dorsal-thalamic (from the own nucleus of the dorsal horn of the opposite side)

descending:

1) cortical-spinal (pyramidal) lateral - ensures the execution of conscious movements

2) red nuclear-spinal - formed by axons of cells of the red nucleus of the midbrain (control of muscle tone)

3. ventral - ascending and descending paths:

ascending:

spinal-thalamic ventral (from the own nucleus of the dorsal horn of the opposite side) - the path of touch and pressure

descending:

1) vestibulo-spinal - formed by axons of neurons of the vestibular nuclei of the medulla oblongata (Deiters, Roller) - balance reflexes

2) cortical-spinal (pyramidal) ventral - the path of voluntary motor reactions

3) tegmental-spinal - from the roof of the midbrain from the cells of the visual and auditory hills

segmental (own) apparatus of the spinal cord:

Place of closure of unconditioned (innate) reflexes from skin receptors to muscles and blood vessels

More ancient in development

relate:

1) gray matter of the spinal cord

2) own bundles (associative pathways)

3) spinal nodes

4) spinal nerve roots

conduction apparatus of the spinal cord:

Associated with different parts of the brain

Conditioned and unconditioned reflexes pass from various analyzers (olfactory, visual, auditory, vestibular)

Later origin, arose as a result of the development of muscles and parts of the brain

relate:

Gray matter of the spinal cord

Ascending and descending tracts connecting the spinal cord with different parts of the brain

Ventral (motor) roots of spinal nerves

Question 2

Meninges of the spinal cord

dura mater spinalis:

ü consists of PST, expelled from the inside by the endothelium

ü external, covers the spinal cord with a sheath and suspends it in the spinal canal

ü between the hard shell and the periosteum of the spinal canal - epidural space filled with fat and vein plexus (shock protection + mobility in the spinal canal)

ü passes to the spinal nerves, forming sheaths on them

arachnoid - arachnoidea spinalis:

ü thin translucent, consists of PCT, covered with endothelium on both sides

ü closely adheres to the hard shell, separating with slit-like subdural space filled with PCT

ü connect with the hard shell: vessels, dentate ligaments of the soft shell and the nerves to which it passes

separated from the soft shell subarachnoid space filled with CSF (cerebrospinal fluid)

soft (vascular) membrane - pia mater spinalis:

ü firmly fuses with the brain, since, accompanying the vessels, it is introduced with them into the medulla

from the side of the subarachnoid space covered with endothelium

ü on the lateral surfaces of the spinal cord forms left and right lateral ligaments . From them between the segments of the brain to the hard shell depart dentate ligaments piercing the arachnoid

ü soft + arachnoid shells - leptomeninx (their inflammation is leptomeningitis)

fixing apparatus of the spinal cord:

1. dura mater- fixed on the ventral arch of the atlas, epistrophy tooth, along the edges of the intervertebral foramina and in the caudal vertebrae

2. dentate ligaments- attach the spinal cord in the soft shell to the arachnoid and hard shells

3. numerous threads, partitions connective tissue that connects the pia mater with the arachnoid

4. spinal nerve roots- leaving through the intervertebral foramen, the brain is suspended "on stretch marks"

ü shells, the contents of the intershell spaces, the fixing apparatus hold the spinal cord, protect against compression during movements of the spine

Question 3

spinal vessels:

spinal arteriesare spinal branches:

1) vertebral and deep cervical a. (cervical region)

2) dorsal intercostal aa. (chest)

3) lumbar aa. (lumbosacral)

ü these branches penetrate the spinal canal along the roots of the spinal nerves and form on the spinal cord 3 longitudinal arterial highways

3 arterial highways of the spinal cord:

1. unpaired ventral spinal a.- lies along with the vein of the same name in the ventral median fissure, gives branches to the gray medulla

2. paired spinal dorsal aa.- lie along the dorsal nerve roots, and the corresponding veins - along the ventral roots

ü 3 lines anastomose with each other in each segment, forming vascular crown . Branches depart from it in the white medulla, connecting with a. gray matter

ü blood flows from the veins into the internal vertebral venous plexus and the paired vertebral ventral sinus (in the epidural space and connects to the segmental veins)

Question 4

Spinal cord development

phylogenesis:

Development is related to the evolution of skeletal muscles

First found in chordates

at the lancelet primitive, in the form of a tube. Nerve cells are scattered throughout the brain. Nerve fibers are unmyelinated gray color. Nerves depart from the brain asymmetrically, because. peristaltic movements. Nerve roots are not divided into sensory and motor. From shells - primitive soft

in fish- the concentration of neurons and the formation of the gray medulla. The ventral columns are developed, the dorsal columns are not developed, because weak skin sensitivity. The roots of the spinal nerves are divided into motor and sensory

in amphibians and reptiles dura mater appears

with land access and the appearance of limbs in the spinal cord, 2 thickenings are formed, the gray matter becomes in the form of H, sensitive cells are evicted to the spinal nodes. With the reduction of the tail as an organ of movement, the spinal cord is shortened

in mammals a spider vein appears

ontogenesis:

Developing from ectoderm→1. neural plate→ 2. neural groove, bounded by neural folds → 3. neural tube, when closing the edges of the groove

ü if the neural plate is divided into 2 - 2 spinal cords - diplomacy

if the ectoderm over the neural tube does not close, then the spinal cord remains open - rashis

The cells of the single layered neural tube are divided into glioblasts (neuroglia) and neuroblasts (neurons)

The neural tube becomes three-layered

Nervous system

The nervous system unites parts of the body (integration), ensures the regulation of various processes, coordination of the work of organs and the interaction of the body with the external environment. It takes in a variety of information from external environment And internal organs, processes it and generates signals that determine adequate responses.

Anatomically, the nervous system is divided into central (brain and spinal cord) and peripheral (peripheral nerve nodes, nerve trunks and nerve endings). From a physiological point of view, a distinction is made between the autonomic (vegetative) nervous system, which innervates the internal organs, glands, blood vessels, and the somatic (cerebrospinal), which regulates the activity of the rest of the body (skeletal muscle tissue).

Development nervous system

The development of the nervous system comes from the neuroectoderm (neural plate), which forms the neural tube, neural crest, and neurogenic placodes. The spinal cord and brain develop from the neural tube, in which the following layers differentiate:

Inner limiting membrane;

ependymal layer;

Raincoat layer;

edge veil;

Outer boundary membrane.

source of all cells The CNS are the matrix (ventricular) cells of the inner layer. They are concentrated near the inner boundary membrane, actively multiply and move. Cells that have completed proliferation - neuroblasts, as well as glioblasts capable of proliferation, are evicted into the mantle layer. Part of the ventricular cells remains in situ, in the future it is the future ependyma.

Neuroblasts give rise to all CNS neurons; after migration, they lose their ability to proliferate. Glioblasts become precursors of macroglia, they are capable of proliferation.

The rigidity of the organization of the brain is determined by two factors: targeted migration of cells and directed growth of processes. The mechanism of directed movements is due to chemotropism, which is carried out along a pre-marked path. At certain stages of ontogeny, programmed cell death occurs. The volume of the subpopulation of dying neurons is estimated in the range of 25-75%. At the same time, the cellular elements of the ganglionic plate form spinal and autonomic nodes.

Spinal cord

The spinal cord is a section of the central nervous system, which is located in the spinal canal and has the form of a rounded cord, slightly flattened in the dorsal-abdominal direction. In the center of the spinal cord runs the central spinal canal, lined with ependymal glia.

The spinal cord, like the brain, is covered by three meninges:

Inner - pia mater with vessels and nerves in its loose connective tissue. It is directly adjacent to the spinal cord.

This is followed by a thin layer of loose connective tissue - the arachnoid. Between these membranes there is a subarachnoid (subarachnoid) space with thin connective tissue fibers connecting the two membranes. This space with cerebrospinal fluid communicates with the ventricles of the brain.

The outer shell is a dura mater, consisting of dense connective tissue, fused with the periosteum in the cranial cavity. In the spinal cord there is an epidural space between the periosteum of the vertebrae and the dura mater, filled with loose fibrous connective tissue, which gives some mobility to the membrane. Between the dura mater and the arachnoid there is a subdural space with a small amount of fluid. The subdural and subarachnoid spaces are internally covered with a layer of squamous glial cells.

The spinal cord consists of two symmetrical halves, delimited from each other in front - by the median fissure, from behind - by the median sulcus.

On a transverse section, gray and white matter are easily distinguished.

Gray matter located in the central part, surrounded by white matter.

The gray matter in cross section has the shape of butterfly wings. The protrusions of the gray matter are called horns: there are anterior, posterior and lateral horns. There is an intermediate zone between the anterior and posterior horns. The horns are actually pillars that run along the spinal cord.

The gray matter of both symmetrical halves is connected to each other in the region of the spinal canal by a central gray commissure (formed by commissures).

Gray matter is formed by the bodies of nerve cells, their dendrites and partially axons, as well as glial cells.

Nerve cells are located in the gray matter in the form of not always sharply demarcated clusters - nuclei. Based on the location of neurons, the nature of their connections and the function of B. Rexedom, 10 plates were isolated in the gray matter of the spinal cord. The topography of the nuclei corresponds to the topography of the plates, although they do not always coincide.

depending from axon topography spinal cord neurons are divided as follows:

♦ Internal - neurons whose axons terminate within the gray matter of a given segment of the spinal cord.

♦ Beam - their axons form bundles of fibers in the white matter of the spinal cord.

♦ Radicular - their axons exit from the spinal cord as part of the anterior roots.

In the posterior horns there are: spongy layer, gelatinous substance, posterior horn proper nucleus and thoracic nucleus.

spongy layer stretches continuously along the spinal cord, forming the dorsal lobe of the posterior horn, which corresponds to plate I, is characterized by a glial skeleton, which contains a large number of small intercalary neurons. These neurons respond to pain and temperature stimuli and give off fibers to the spinothalamic tract on the opposite side. Among these neurons there are cells containing substance P and enkephalin.

In gelatinous substance, or Roland gelatinous substance(plate II, III), glial elements predominate. Nerve cells here are small, there are few of them. They are approached by axons coming from the posterior funiculus, and fibers of pain and tactile sensitivity. The axons of the neurons of this layer either end within this segment of the spinal cord (they enter the marginal Lissauer belt, which forms transverse and longitudinal connections on the surface of the gelatinous substance), or go into their own bundles or to the thalamus, cerebellum, and lower olives. The neurons of this layer produce enkephalin, an opioid-type peptide that inhibits pain effects.

The main significance of the gelatinous substance is the implementation of an inhibitory effect on the functions of the spinal cord by controlling the sensory information entering it: skin, partially visceral and proprioceptive.

Own core consists of intercalary neurons that receive afferent impulses from the spinal nodes and descending brain fibers. Their axons pass through the anterior white commissure to the opposite side and ascend to the thalamus, just as the gelatinous substance is responsible for exteroceptive sensitivity.

The thoracic nucleus of the posterior horn (Clark's nucleus) is located in the VII plates. It is formed by neurons to which thick myelinated collaterals of sensory neurons approach, delivering proprioceptive sensory input from the joints, tendons, and muscles. The axons of Clark's nucleus cells form the posterior spinal cerebellar tract.

In the intermediate zone of the VI and partially VII plates, the outer and inner basilar nuclei are located. They process the bulk of the information coming from the brain and transmit it to motor neurons. On the cells of the outer nucleus, thick, fast-conducting axons are interrupted, originating from the largest and giant pyramids of the motor zone of the cerebral cortex. Thin slowly conducting fibers are projected onto the neurons of the inner nucleus. In humans, about 90% of the fibers of the cortico-spinal tract end on the neurons of the basilar nuclei.

Lateral horns contain: medial and lateral nuclei.

The lateral nucleus (Th I - L II) contains the neurons of the autonomic reflex arc - the center of the sympathetic department. The axons of the pseudounipolar spinal ganglion enter the sympathetic nucleus, carrying visceral sensitivity. The second group of axons comes from the medial nucleus of the lateral horn. The axons of the neurons of the lateral nucleus give rise to preganglionic fibers emerging from the spinal cord through the anterior roots.

The medial nucleus (S II - Co III) is located in the intermediate zone, where there are no lateral horns - it receives impulses from sensitive neurons of the autonomic reflex arc.

In addition, the Onufrovich nucleus is located in the lateral horns of the sacral segments (S2 - S4) of the spinal cord. It contains neurons of the parasympathetic division of the autonomic nervous system, which are involved in the innervation of the pelvic organs.

Plate VII contains the Renshaw interoneurons necessary for the implementation of the motor function. They receive an excitatory impulse from the axon collagens of motor neurons and inhibit their function. It has importance for the coordinated work of motor neurons and the muscles innervated by them for alternate flexion and extension of the limbs.

The interstitial nucleus of Cajal is localized in the VIII plate. Its interoneurons switch information from afferent neurons to motor neurons. The axons of the neurons of this nucleus are part of their own bundles and form collateral connections on several segments.

The periependymal gray matter corresponds to plate X, is located throughout the spinal cord and is formed by intercalary neurons of the autonomic nervous system.

The anterior horns contain multipolar motor neurons (lamina IX), which are the only executive cells in the spinal cord that send information to the skeletal muscles. They are combined into nuclei, each of which usually stretches for several segments. Ends on motor neurons:

♦ Collaterals of axons of pseudo-unipolar cells, forming two-neuronal reflex arcs with them.

♦ Axons of intercalary neurons, whose bodies lie in the posterior horns of the spinal cord.

♦ Axons of Renshaw cells forming inhibitory axosomatic synapses. The bodies of these small cells are located in the middle of the anterior horn and are innervated by the collaterals of the axons of motor neurons.

♦ Fibers of the descending pathways of the pyramidal and extrapyramidal systems, carrying impulses from the cerebral cortex and nuclei of the brain stem.

According to classical concepts, motor neurons in the spinal cord are distributed over 5 motor nuclei.

Medial - anterior and posterior - are present throughout the spinal cord, innervate the muscles of the body.

Lateral - anterior and posterior - are localized in the cervical and lumbar thickenings, innervate the flexors and extensors of the limbs.

The central nucleus - is located in the lumbar and cervical regions, innervates the muscles of the limb belts.

white matter- is divided by the anterior and posterior roots into symmetrical ventral, lateral and dorsal cords. It consists of longitudinally running nerve fibers (mainly myelinated), forming descending and ascending pathways (tracts), and astrocytes. Each tract is characterized by the predominance of fibers formed by neurons of the same type.

The pathways include 2 groups: propriospinal and supraspinal.

propriospinal pathways- own apparatus of the spinal cord, formed by axons of intercalary neurons, which communicate between the segments of the spinal cord. These paths pass mainly on the border of white and gray matter as part of the lateral and ventral cords.

supraspinal pathways- provide a connection between the spinal cord and the brain and include ascending and descending spinal-cerebral pathways.

Pain, temperature, deep and tactile sensitivity are carried out along the ascending paths. These are the dorsal and thalamic pathway, the dorsal and ventral spinal cerebellar pathways, the tender and sphenoid bundles.

The cerebrospinal tracts provide the transmission of impulses to the brain. Some of them (there are 20 in total) are formed by the axons of the cells of the spinal nodes, while the majority are represented by the axons of various intercalary neurons, the bodies of which are located on the same or on the opposite side of the spinal cord.

Cerebrospinal tracts include pyramidal and extra-rapyramidal systems.

The pyramidal system is formed by long axons of the pyramidal cells of the cerebral cortex, which at the level of the medulla oblongata mostly pass to the opposite side and form the lateral and ventral corticospinal tracts. The pyramidal system controls the precise voluntary movements of the skeletal muscles, especially the limbs.

The extrapyramidal system is formed by neurons, the bodies of which lie in the nuclei of the midbrain and medulla oblongata and the bridge, and the axons end on motor neurons and intercalary neurons. This system controls mainly the contraction of the tonic muscles responsible for maintaining the posture and balance of the body.

Extrapyramidal descending pathways are represented by the rubrospinal pathway, originating from the red nucleus and conducting an impulse from the nuclei of the cerebellum, as well as the tecto-spinal pathway, starting from the tire and conducting impulses from the visual and auditory pathways, as well as the vestibulo-spinal pathway, originating from the nuclei of the vestibular nerve and carrying impulses of a static nature.

Spinal cord- an organ of the central nervous system of vertebrates located in the spinal canal.

The spinal cord looks like a strand white color, somewhat flattened from front to back in the area of ​​thickenings and almost round in other departments. In the spinal canal, it extends from the level of the lower edge of the foramen magnum to the intervertebral disc between the 1st and 2nd lumbar vertebrae. At the top, the spinal cord passes into the brainstem, and at the bottom, gradually decreasing in diameter, it ends with a cerebral cone. In adults, the spinal cord is much shorter than the spinal canal, its length varies from 40 to 45 cm, weight is about 34-38 g, which is approximately 2% of the mass of the brain. The cervical thickening of the spinal cord is located at the level of the III cervical and I thoracic vertebrae; the lumbosacral thickening is located at the level of the X-XII thoracic vertebra. The anterior median fissure and posterior median sulcus divide the spinal cord into symmetrical halves. On the surface of the spinal cord, at the exit points of the ventral (anterior) and dorsal (posterior) roots, two less deep furrows are revealed: the anterior lateral and the posterior lateral. The segment of the spinal cord corresponding to two pairs of roots (two anterior and two posterior) is called segment. The anterior and posterior roots emerging from the segments of the spinal cord unite into 31 pairs of spinal nerves. The anterior root is formed by the processes of motor neurons of the nuclei of the anterior columns of gray matter. The composition of the anterior roots of the VIII cervical, XII thoracic, two upper lumbar segments, along with the axons of motor somatic neurons, includes neurites of the cells of the sympathetic nuclei of the lateral columns, and the anterior roots of the II-IV sacral segments include the processes of neurons of the parasympathetic nuclei of the lateral intermediate substance of the spinal cord. The posterior root is represented by the central processes of pseudo-unipolar (sensitive) cells located in the spinal ganglion. The central canal passes through the gray matter of the S. along its entire length, which, expanding cranially, passes into the IV ventricle of the brain, and in the caudal part of the cerebral cone forms the terminal ventricle.

The spinal cord carries 31 pairs of spinal nerves symmetrically located on both sides: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and one coccygeal.

White and gray matter of the spinal cord

On the cross sections of the spinal cord, the ratio of the location of white and gray matter is visible. The gray matter occupies the central part and has the shape of a butterfly with spread wings, or the letter "H". The white matter is located around the gray, occupying the periphery of the spinal cord. The white matter of the spinal cord is mainly a complex system of varying lengths and thicknesses of the fleshy and partly non-fleshy nerve fibers and the supporting nervous tissue- neuroglia, as well as blood vessels surrounded by a small amount of connective tissue. The white matter of one half of the spinal cord is connected with the white matter of the second half by a thin white commissure running transversely in front of the central canal. Nerve fibers in the white matter are collected in bundles. The indicated three grooves running along the fissure on each half of the spinal cord delimit the white matter of each half into three so-called cords of the spinal cord. There are anterior, lateral and posterior cords. In the upper sections of the thoracic and entire cervical parts of the spinal cord, the posterior cord is divided into two bundles - thin and wedge-shaped. These cords continue into the initial part of the brain - the medulla oblongata. In the lower parts of the spinal cord, the listed cords merge and become indistinguishable.

The spinal cord has a segmental, bilateral structure. Its inner nucleus is formed by gray matter, consisting of neuronal cells, unmyelinated axons, glial cells, and blood vessels. The outer white matter consists of bundles of myelinated axons that transmit impulses to and from the spinal cord.

The gray matter is the pillars, and on the cut, the horns ( cornu anterius, posterius). The anterior and posterior horns are connected by an intermediate zone of gray matter (Fig. 1), which forms the lateral horns - cornu laterale(from Ⅰ of the thoracic to Ⅱ - Ⅲ of the lumbar vertebrae).

Rice. 1.: 1 - posterior horn; 2 - lateral horn; 3 - front horn; 4 - rear funiculus; 5 - lateral cord; 6 - anterior cord.

In the posterior horns, nerve cells receive information from the body's sensory nerve cells about parameters such as touch, temperature, muscle activity, and body balance. Located only in the central part of the spinal cord, the nerve cells of the lateral horns monitor and regulate the functioning of the internal organs. The anterior horns contain nerve cells that transmit impulses along nerve fibers to the muscles of the skeleton, causing them to contract and move.

In the posterior horn are the spongy zone and the gelatinous substance (their processes form their own bundles of the spinal cord, providing a connection between the segments), the proper and thoracic nuclei, and between the posterior and lateral horn is the reticular formation of the spinal cord.

The lateral horn contains the medial intermediate nucleus (sensory) and the lateral intermediate nucleus (vegetative, sympathetic) (Fig. 2). Between the anterior and posterior horns in the sacral segments (S II - S IV) are the parasympathetic nuclei.

Rice. 2. Pathways of the white matter (1-12) and the location of the nuclei of the gray matter (13-17) in the spinal cord; cross section (scheme): 1 - a thin beam; 2 - wedge-shaped bundle; 3 - lateral cortical-spinal path; 4 — krasnoyaderno-spinal path; 5 - lateral spinal-thalamic path; 6 - roof-spinal path; 7 - anterior spinothalamic path; 8 - posterior spinal tract; 9 - anterior spinal tract; 10 - reticulospinal fibers; 11 - pre-door-spinal path; 12 - anterior cortical-spinal path; 13 - own core; 14 - thoracic nucleus; 15 - medial intermediate nucleus; 16 - lateral intermediate nucleus; 17 - motor nuclei of the anterior horn.

The anterior horn contains 5 motor nuclei (anteromedial, anterolateral, posteromedial, posterolateral, central), as well as motor nuclei of the accessory and phrenic nerves. In one segment, there are about 3 thousand motor neurons.

In the motor nuclei there are: large motor neurons for the pyramidal pathways, small ones for the extrapyramidal and gamma motor neurons for the reticular pathways.

Thanks to the connections between the motor nuclei, the following are established:

• center of gravity;
• coordination of movements of the trunk and limbs;
• coordination of movements of the right and left limbs when walking and running.

The bulk of the gray matter is scattered cells ( cellulae disseminatae) related to the intrinsic apparatus of the spinal cord.

Gray matter of the spinal cord, substantia grisea (see fig.,), consists mainly of the bodies of nerve cells with their processes that do not have a myelin sheath. In addition to them, in the gray matter there are processes of those nerve cells that are located in other parts of the spinal cord and brain, neuroglia, as well as blood vessels and their accompanying connective tissue.

In the gray matter, there are two lateral parts located in both halves of the spinal cord, and a transverse part connecting them in the form of a narrow bridge - . It continues into the lateral parts, occupying their middle, as lateral intermediate (gray) substance, substantia (grisea) intermedia lateralis.

In the middle sections of the central intermediate gray matter there is a very narrow cavity - central canal, canalis centralis. At different levels of the spinal cord, its lumen in a horizontal section has a different size and shape: in the region of the cervical and lumbar thickenings - oval, and in the chest - rounded with a diameter of up to 0.1 mm. In adults, the canal cavity in a number of areas may overgrow. The central canal stretches throughout the entire spinal cord, passing at the top into the cavity of the IV ventricle. Below, in the region of the cerebral cone, the central canal is expanded and its diameter reaches an average of 1 mm; this section of the central canal is called terminal ventricle, ventriculus terminalis.

The tissue surrounding the central canal of the spinal cord and consisting mainly of neuroglia and a small number of neurons with their fibers is called central gelatinous substance, substantia gelatinosa centralis.

The central intermediate (gray) matter surrounding the central canal is divided into two parts. One part is located in front of the canal and is adjacent to the white commissure that connects the anterior cords of both halves of the spinal cord. The other part lies behind the canal. Behind the central intermediate (gray) substance, directly adjacent to the posterior median septum, is located .

Each of the lateral parts of the gray matter forms three protrusions: a thicker anterior one, a narrower posterior one, and between them a small lateral protrusion, which is not expressed at all levels of the spinal cord. The lateral protrusion is especially clearly visible in the lower segments of the cervical part and in the upper segments of the thoracic part of the spinal cord.

Protrusions throughout the spinal cord form gray pillars, columnae griseae. Each of them on the transverse section of the spinal cord receives the name horns, cornu(see fig. , ). Distinguish anterior column, columna ventralis, on the cross section - anterior horn, cornu ventrale, rear column, columna dorsalis (posterior horn, сornu dorsale), And lateral column, columna lateralis (lateral horn, cornu laterale).

The anterior horn is much wider, but shorter than the posterior one, and does not reach the periphery of the spinal cord, while the posterior horn, narrower and longer, reaches the outer surface of the brain.

In the posterior horn can be seen apex of the posterior horn, apex cornus dorsalis, - the narrowest part of the dorsal posterior horn, surrounding head of the posterior horn, caputcornus dorsalis, which goes into neck of the posterior horn, cervix cornus dorsalis, and that in turn - in the widest part of the posterior horn - base of the posterior horn, basiscornusdorsalis(see fig.).

The apex of the posterior horn is bordered by an area rich in neuroglia, with a large number of nerve cells, which is called gelatinous substance, substantia gelatinosa.

Nerve cells in the gray matter form clusters - the nuclei, or centers, of the spinal cord, which have their own constant topography (Fig. 883).

1. In front pillar motor nuclei lie, the cells of which send their axons to the composition of the anterior roots of the spinal cord:

1. anterolateral nucleus, nucleus ventrolateralis, which has two parts: the upper one, lying in the segments C IV -C VIII, and the lower one, located in the segments L II -S I;
2. anterior medial nucleus, nucleus ventromedialis, often also represented by two parts: the upper one in C II -L IV and the lower one in S II -Co I; less often these parts do not have a break in the segments (L V –S I);
3. posterolateral nucleus, nucleus dorsolateralis, divided into two parts: the larger upper one in C V–C VIII and the lower one in L III–S II;
4. posterolateral nucleus, nucleus retrodorsolateralis, lies posterior to the previous one. It is represented by two small clusters of cells in C VIII -Th I and in S I -S III;
5. posteromedial nucleus, nucleusdorsomedialis, is represented by a small upper part lying in the upper cervical segment C I, and lower - in the segments Th I -S II ;
6. central nucleus, nucleus centralis, more often located in segments Th I–L III, but may also have an additional part in S I–S V;
7. accessory nerve nucleus, nucleusn. accessorii, usually limited to C I–C VI segments;
8. phrenic nerve nucleusnucleus n. phrenici, occurs in segments C IV–C VII;
9. lumbar dorsal nucleus,nucleus lumbodorsalis, lies in segments L III - S I .

2. In rear pillar sensitive nuclei lie:

1. gelatinous substance, substantia gelatinosa, has the appearance of a crescent on a transverse section, bordering the top of the posterior horn;
2. own nucleus of the posterior horn, nucleus proprius cornus posterioris(BNA), located in its central part, occupies almost its entire area and extends along the entire posterior column (C I –Co I);
3. secondary visceral substance, substantia visceralis secundaria, lies somewhat dorsal to the central intermediate (gray) substance.

3. side post contains the following kernels:

1. thoracic column [thoracic nucleus], ​​columna thoracica, is limited by segments Th I -L II and is located on the medial side of the base of the posterior horn, so some authors attribute it to the nuclei of the latter;
2. central intermediate (gray) substance, substantia (grisea) intermedia centralis, is localized in segments Th I –L III, in central department lateral horn, almost reaching the central canal;
3. lateral intermediate (gray) substance, substantia (grisea) intermedialateralis, lies lateral to the previous nucleus, occupying the protrusion of the lateral horn and spreading to segments Th I–L III;
4. sacral parasympathetic nuclei,nuclei parasympathetic sacrales, occupy segments S II –S IV, located somewhat ahead of the previous one.

In the lower cervical and upper thoracic segments of the spinal cord, in the angle between the lateral horn and the lateral edge of the posterior horn, gray matter in the form of processes penetrates into the white matter, forming a reticular structure - reticular formation, formatio reticularis, spinal cord, in the loops of which the white matter is located.

The location of the anterior and posterior horns corresponds to the anterior and posterolateral grooves of the spinal cord. This correspondence between the horns and the sulci determines the topography of the white matter in transverse sections: its division into anterior, posterior, and lateral cords of the white matter.