Spinal nerves are classified according to their function. Anatomy and structure of spinal nerves in the human body, functions and dysfunctions

Rice. 995. Spinal cord segment (semi-schematic).

Spinal nerves, nn. spinales (Fig. , , ), are paired (31 pairs), metamerically located nerve trunks:

1. Cervical nerves, nn. cervicales(C I–C VII), 8 pairs
2. Thoracic nerves, nn. thoracici(Th I – Th XII), 12 pairs
3. Lumbar nerves, nn. lumbales(L I –L V), 5 pairs
4. Sacral nerves, nn. sacrales(S I –S V), 5 pairs
5. Coccygeal nerve, n. coccygeus(Co I – Co II), 1 pair, less often two.

The spinal nerve is mixed and is formed by the fusion of two roots belonging to it:

1) dorsal root [sensitive], radix dorsalis, And

2) anterior root [motor], radix ventralis.

Each root is connected to the spinal cord radicular threads, fila radicularia. The dorsal root in the region of the posterolateral sulcus is connected to the spinal cord by radicular filaments of the dorsal root, fila radicularia radicis dorsalis, and the anterior root in the area of ​​the anterolateral groove - radicular filaments of the anterior root, fila radicularia radicis ventralis.

The posterior roots are thicker, since each of them belongs spinal ganglion [sensitive], ganglion spinale. The exception is the first cervical nerve, whose anterior root is larger than the posterior one. Sometimes there is no node in the root of the coccygeal nerve.

The anterior roots do not have nodes. At the site of formation of the spinal nerves, the anterior roots are only adjacent to the spinal ganglia and are connected to them using connective tissue.

The connection of the roots into the spinal nerve occurs lateral to the spinal ganglion.

The roots of the spinal nerves first pass through the subarachnoid space and are surrounded directly by the pia mater. The dentate ligament runs between the anterior and posterior roots in the subarachnoid space. Near the intervertebral foramina, the roots are densely covered with all three meninges, which grow together and continue into the connective tissue sheath of the spinal nerve (see Fig. , , ).

The roots of the spinal nerves are directed from the spinal cord to the intervertebral foramen (see Fig.,):

1) the roots of the upper cervical nerves are located almost horizontally;

2) the roots of the lower cervical nerves and two upper thoracic nerves go obliquely downward from the spinal cord, located before entering the intervertebral foramen one vertebra below the point of origin from the spinal cord;

3) the roots of the next 10 thoracic nerves follow even more obliquely downwards and, before entering the intervertebral foramen, are approximately two vertebrae below their origin;

4) the roots of the 5th lumbar, 5th sacral and coccygeal nerves are directed downwards vertically and form with the roots of the same name on the opposite side ponytail, cauda equina, which is located in the cavity of the dura mater.

Separating from the cauda equina, the roots are directed outward and, while still in the spinal canal, unite into spinal nerve trunk, truncus n. spinalis.

Most spinal nodes lie in the intervertebral foramina; the lower lumbar nodes are located partially in the spinal canal; The sacral nodes, except the last one, lie in the spinal canal outside the dura mater. The spinal ganglion of the coccygeal nerve is located inside the cavity of the dura mater. Spinal nerve roots and spinal nodes can be examined after opening the spinal canal and removing the vertebral arches and articular processes.

All trunks of the spinal nerves, with the exception of the first cervical, fifth sacral and coccygeal nerves, lie in the intervertebral foramina, while the lower ones, which take part in the formation of the cauda equina, are also partially located in the spinal canal. The first cervical spinal nerve (C I) passes between the occipital bone and the first cervical vertebra; the eighth cervical spinal nerve (C VIII) is located between the VII cervical vertebra and the I thoracic vertebra; the fifth sacral and coccygeal nerves exit through the sacral fissure.

The spinal nerve trunks are mixed, that is, they carry sensory and motor fibers. Each nerve upon exiting the spinal canal almost immediately divides into anterior branch, r. ventralis, And posterior branch, r. dorsalis, each of which contains both motor and sensory fibers (see Fig. , , , ). The spinal nerve trunk through connecting branches, rr. communicantes, is associated with the corresponding node of the sympathetic trunk.

There are two connecting branches. One of them carries prenodal (myelin) fibers from the cells of the lateral horns of the spinal cord. It is white [these branches are from the eighth cervical (C VIII) to the second or third lumbar (L II – L III) spinal nerve] and is called white connecting branch, r. communications albus. Another connecting branch carries postnodal (mostly unmyelinated) fibers from the nodes of the sympathetic trunk to the spinal nerve. It is darker in color and is called gray connecting branch, r. communications griseus.

A branch extends from the trunk of the spinal nerve to the dura mater of the spinal cord - meningeal branch, r. meningeus, which also contains sympathetic fibers.

The meningeal branch returns to the spinal canal through the intervertebral foramen. Here the nerve is divided into two branches: a larger one, running along the anterior wall of the canal in an ascending direction, and a smaller one, running in a descending direction. Each of the branches connects both with the branches of neighboring branches of the meninges, and with the branches of the opposite side. As a result, a plexus of the meninges is formed, which sends a branch to the periosteum, bones, membranes of the spinal cord, venous vertebral plexuses, as well as to the arteries of the spinal cord. In the neck area, spinal nerves take part in the formation vertebral plexus, plexus vertebralis, around the vertebral artery.

Posterior branches of the spinal nerves

Posterior branches of the spinal nerves, rr. dorsales nn. spinalium (see Fig. , , ), with the exception of the two upper cervical nerves, are much thinner than the anterior ones. All posterior branches from their origin, at the lateral surface of the articular processes of the vertebrae, are directed back between the transverse processes of the vertebrae, and in the region of the sacrum they pass through the dorsal sacral foramina.

Each posterior branch is divided into medial branch, r. medialis, and on lateral branch, r. lateralis. Both branches contain sensory and motor fibers. The terminal branches of the posterior branches are distributed in the skin of all dorsal regions of the body, from the occipital to the sacral region, in the long and short muscles of the back and in the muscles of the back of the head (see Fig. , , ).

Anterior branches of the spinal nerves

Anterior branches of the spinal nerves, rr. ventrales nn. spinalium , thicker than the posterior ones, with the exception of the first two cervical nerves, where there are inverse relationships.

The anterior branches, in addition to the thoracic nerves, are widely connected to each other near the spinal column and form plexus, plexus. Of the anterior branches of the thoracic nerves, branches from Th I and Th II, sometimes Th III (brachial plexus), and from Th XII (lumbar plexus) take part in the plexuses. However, these branches only partially enter the plexus.

Topographically, the following plexuses are distinguished: cervical; shoulder; lumbosacral, in which the lumbar and sacral are distinguished; coccygeal (see fig.).

All these plexuses are formed by connecting the corresponding branches in the form of loops.

The cervical and brachial plexuses are formed in the neck, the lumbar - in the lumbar region, the sacral and coccygeal - in the pelvic cavity. Branches depart from the plexuses, which go to the periphery of the body and, branching out, innervate its corresponding sections. The anterior branches of the thoracic nerves, which do not form plexuses, continue directly to the periphery of the body, branching in the lateral and anterior sections of the walls of the chest and abdomen.

Lumbar, sacral and coccygeal nerves

Lumbar, sacral and coccygeal nerves, nn. lumbales, sacrales et coccygeus , like all overlying spinal nerves, give off 4 groups of branches: meningeal, connective, anterior and posterior.

The anterior branches of the lumbar, sacral and coccygeal spinal nerves (L I–L V, S I–S V, Co I–Co II) form one common lumbosacral plexus, plexus lumbosacralis.

In this plexus, the lumbar plexus (Th XII, L I -L IV) and the sacral plexus (L IV -L V -Co I) are topographically distinguished. The sacral plexus is divided into the sacral plexus itself and the coccygeal plexus (S IV – Co I, Co II) (see Fig.).

Spinal nerves arise in pairs from segments of the spinal cord (31 pairs in total); are formed from the anterior (motor) and posterior (sensitive) roots, which connect at the intervertebral foramina. The sensitive spinal ganglion is adjacent to the dorsal root. Spinal nerves are structural elements of the reflex arcs of the human nervous system (Fig. 5.11).

Rice. 5.11.

1 - receptor; 2 - sensory neuron; 3 - motor neuron; 4 - interneuron; 5 - synapses; 6* - effector

Here are some patterns of distribution of spinal nerves.

• - according to the “grouping of the body around the nervous system” (F. Engels), the nerves diverge to the sides from the midline on which the nervous system (spinal cord and brain) is located;
• - according to the structure of the body, according to the principle of bilateral symmetry, the nerves are paired and run symmetrically;
• - nerves go to certain segments of the human body;
• - nerves travel the shortest distance from the point of exit from the brain or spinal cord to the organ;
• - superficial nerves (cutaneous) accompany the saphenous veins, deep nerves accompany the arteries and veins;
• - nerves embedded in neurovascular bundles are located on the flexor surfaces of the body, in protected places;
• - each spinal nerve immediately upon exiting the foramen is divided into four branches: anterior, posterior, meningeal, connective;
• - the meningeal branch returns to the membranes of the spinal cord, innervating it;
• - the connecting branch serves to connect the nerve segment with the sympathetic node;
• - the posterior branch extends metamerically to a certain area of ​​the body and innervates the skin and muscles of the back of the head, back, and lower back;
• - the anterior branch retains a metameric structure only in the thoracic region (intercostal nerves), and in the rest it forms plexuses in the form of loops.

Distinguish four main plexuses spinal nerves (Fig. 5.12 and 5.13): cervical; shoulder; lumbar; sacral Peripheral nerves arise from all plexuses.

Rice. 5.12.

I- cervical plexus; 2 - brachial plexus; 3 - intercostal nerves;

4 - sympathetic trunk; 5 - median nerve; 6 - radial nerve; 7 - lumbar plexus; 8 - ulnar nerve; 9 - sacral plexus; 10 - coccygeal nerves;

II - femoral nerve; 12 - sciatic nerve; 13 - obturator nerve;

14 - tibial nerve; 15 - saphenous nerve; 16 - common peroneal nerve

Cervical plexus formed by the anterior branches of the four superior cervical nerves; located on the deep muscles of the neck. Peripheral nerves extending from the plexuses are divided into cutaneous (sensory), muscular (motor), and mixed (see Table 5.5).

TO sensory nerves include:

• - great auricular nerve, innervating the external ear;
• - lesser occipital nerve (skin of the occipital region);
• - transverse cervical nerve (skin of the anterior neck);
• - supraclavicular nerves (skin of the lateral neck above the collarbone). Motor nerves are represented by muscle branches, which

innervate the neck muscles located in the middle and deep layer.

TO mixed nerves The phrenic nerve innervates the diaphragm, pleura, pericardium, and part of the peritoneum.

Brachial plexus formed by the anterior branches of the four lower cervical nerves and partly the first thoracic nerve. It passes through three trunks into the axillary region between the first rib and the clavicle along with the vessels. The plexus is divided into: the supraclavicular part (mainly short branches); subclavian part (long branches) (see Table 5.6).

Among short branches highlight:

Dorsal scapular nerve - to the levator scapulae muscle; rhomboid major and minor muscles;

long thoracic nerve - to the serratus anterior muscle;

• - suprascapular nerve - to the supraspinatus and infraspinatus muscles;
• - lateral and medial pectoral nerves - to the pectoralis major and minor muscles;
• - subscapularis - to the teres major and subscapularis muscles;
• - axillary nerve - innervates the deltoid and teres minor muscles and the skin of the deltoid region.

Long branches brachial plexus include:

The medial cutaneous nerve of the shoulder and the medial cutaneous nerve of the forearm - innervate the corresponding areas of the skin;

ulnar nerve - the skin in the area of ​​the dorsal surface of the hand, IV, V, partially III finger and the palmar surface of the V finger, as well as the flexor muscles of the hand and fingers;

• - median nerve - the skin of the wrist joint, the palmar surface of the I-III and partly the IV finger and the anterior group of muscles of the forearm;
• - musculocutaneous nerve - the skin of the radial side of the forearm and the anterior muscle group of the shoulder;
• - radial nerve - skin in the area of ​​the posterior surface of the shoulder, forearm, dorsum of the hand, I-III fingers and muscles of the posterior group of the shoulder and posterior group of the forearm.

Thoracic nerves they do not give plexuses, they pass in the groove of the corresponding rib, are called intercostal, and the XII - subcostal nerve. The nerves are mixed and innervate the ventral muscles of the chest and abdomen, the skin of the anterior and lateral walls of the abdomen and the mammary gland.

Lumbar plexus formed by the anterior branches of the three upper lumbar nerves, partly the XII subcostal and IV lumbar; located in the thickness of the psoas major muscle. The cutaneous nerves of this plexus innervate the skin of the lower abdomen, partially the thigh, lower leg and foot, and the external genitalia; muscle nerves innervate the muscles of the abdominal walls, the anterior and medial group of thigh muscles (see Fig. 5.13).

The main nerves of the plexus are:

• - muscle branches (short, before the formation of a plexus) - innervate the lumbar major and minor, quadratus lumborum muscle;
• - iliohypogastric nerve - the skin of the anterior abdominal wall and lateral thigh, as well as the anterior and lateral abdominal muscles;
• - ilioinguinal nerve - skin of the groin area, scrotum (in men), labia majora (in women), oblique and transverse abdominal muscles;
• - femoral-genital nerve - the skin of the thigh (anterior surface), scrotum and labia majora, as well as the levator testis muscle, round ligament of the uterus (in men and women, respectively);
• - lateral cutaneous nerve of the thigh - skin of the posterolateral surface of the thigh;
• - obturator nerve - the skin of the lower medial surface of the thigh and the adductor muscles of the thigh;
• - femoral nerve - the skin of the anteromedial surface of the thigh, lower leg, dorsum and medial edge of the foot, as well as the anterior group of thigh muscles.

Rice. 5.13.

• 1 - brain; 2 - cerebellum; 3 - cervical plexus; 4 - brachial plexus;
• 5 - spinal cord; V- sympathetic trunk; 7 - median nerve; 8 - solar plexus; 9 - radial nerve; 10 - ulnar nerve; 11 - lumbar plexus;
• 12 - sacral plexus; 13 - coccygeal plexus; 14 - femoral nerve;
• 15 - sciatic nerve; 16 - tibial nerve; 17 - cutaneous branch of the femoral

nerve; 18 - peroneal nerve

Sacral plexus formed by the anterior branches of the V lumbar, I-IV sacral and partially IV lumbar spinal nerves: located on the anterior surface of the sacrum. The nerves of the plexus innervate the skin of the gluteal region and external genitalia, the skin and muscles of the posterior thigh, lower leg and foot (with the exception of areas innervated by the nerves of the lumbar plexus) (see Table 5.8).

The peripheral branches of this plexus are short and long branches.

Among short branches highlight:

• - obturator internus, piriformis, quadratus femoris nerve, superior and inferior gluteal nerves - innervate the muscles of the pelvic region (piriformis, superior and inferior twins, quadratus femoris, obturator internus and gluteal muscles);
• - pudendal nerve - innervates the skin of the perineum in the anus, cavernous bodies, clitoris and perineal muscles.

Long branches include:

• - posterior cutaneous nerve of the thigh - innervates the skin of the gluteal region, perineum, posterior surface of the thigh and calf region;
• - sciatic nerve - innervates the posterior group of thigh muscles. Its branches are the tibial and common fibular.

The tibial nerve innervates the skin of the posteromedial surface of the leg, the heel and the muscles of the posterior group of the leg. Branches of the tibial nerve: the medial plantar nerve, which innervates the muscles of the eminence of the first toe and the skin of the medial edge of the foot, I-IV fingers, the lateral plantar nerve - the skin of the sole, the fifth toe, the muscles of the little toe group and the middle group of the sole.

The common peroneal nerve (from the sciatic nerve) innervates the skin of the lateral surface of the leg and foot, the biceps femoris muscle, and is divided into superficial and deep peroneal nerves. The superficial peroneal goes to the muscles of the lateral group of the lower leg and the skin of the II-V fingers, the deep peroneal goes to the muscles of the anterior group of the lower leg and the skin of the fingers (the surfaces of the fingers facing each other).

In order to control and consolidate the acquired knowledge in Table. 5.5-5.8 presents systematic data on the anatomy of the spinal nerves.

Table 5.5

Nerves of the cervical plexus

	Innervated area
Lesser occipital nerve	Skin of the occipital region
Greater auricular nerve	Auricle, external auditory canal
Transverse cervical nerve	Skin of the anterior neck, sensory innervation of the subcutaneous muscle of the neck
Supraclavicular	The skin of the lateral area of ​​the neck above the collarbone and the chest wall below the collarbone
Muscular branches	Muscles: long capitis and neck, scalene, rectus capitis, levator scapulae
Diaphragmatic	Diaphragm, pleura, pericardium, peritoneum covering the diaphragm, liver ligaments
Neck loop	Muscles: sternothyroid, thoracnohyoid, scapular-1juglossus, thyroglossus

Brachial plexus nerves

	Innervated area
Dorsal nerve of the scapula	Muscles: levator scapulae, rhomboid major and rhomboid minor
Long thoracic nerve	Serratus anterior muscle
Subclavian nerve	Subclavius ​​muscle
Suprascapular nerve	Muscles: supraspinatus, infraspinatus; shoulder capsule
Subscapular nerve	Subscapularis and teres major muscles
Thoracodorsal	Latissimus dorsi muscle
Lateral and medial thoracic nerves	Pectoralis major and minor muscles
Axillary	Skin of the deltoid region and the upper part of the posterolateral region of the shoulder; deltoid, minor, round muscles; shoulder capsule
Medial cutaneous nerve of the shoulder	Skin of the medial surface of the shoulder to the elbow joint
Medial cutaneous nerve of the forearm	Skin of the ulnar (medial) side of the forearm of the anterior surface to the wrist joint
Ulnar nerve	Joints: elbow, wrist, hand joints; the skin of the eminence of the small finger, the ulnar side of the palm, the radial and ulnar side of the V and ulnar side of the IV fingers, on the dorsum of the hand the skin of the V, IV and ulnar side of the III finger
	Muscles: flexor carpi ulnaris, medial part of the deep flexor digitorum, palmar brevis, eminence of the small finger muscles, palmar and dorsal interosseous, III and IV lumbricals, adductor pollicis, flexor pollicis brevis
Median	Joints: elbow, wrist, hand joints; skin in the area of ​​the wrist joint (front surface), the radial side of the palm of the I-IV fingers, the dorsal surface of the middle and distal phalanges of the I-III fingers. Muscles: pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis and lateral portion of flexor digitorum profundus, flexor pollicis longus, flexor pollicis brevis (superficial head), opposable thumb, I-II lumbricals

	Innervated area
Musculocutaneous nerve	Muscles: biceps brachii, coracobrachialis, brachialis; capsule of the elbow joint; skin of the radial side of the forearm to the eminence of the thumb
Radial nerve	Skin of the posterior and posterolateral surface of the shoulder; skin of the back of the forearm; shoulder joint capsule. Muscles: triceps brachii, ulnaris, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, supinator, extensor digitorum, extensor digitorum, extensor pollicis ulnaris, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis , extensor of the index finger. Skin of the dorsal and lateral sides of the base of the 1st finger, the dorsum of the 1st, 2nd and radial side of the 3rd fingers

Table 5.7

Lumbar plexus nerves

	Innervated area
Muscular branches	Muscles: psoas major and minor, quadratus lumborum
11 iliohypogastric nerve	Muscles: transverse, internal and external obliques, rectus abdominis; skin of the anterior abdominal wall above the pubis and superolateral thigh
Ilioinguinal	Skin of the groin area of ​​the pubis, scrotum (in men), labia majora (in women), superomedial thigh, transverse, external and internal oblique muscles of the abdomen
Femoro-genital	Skin of the thigh below the inguinal ligament; round ligament of the uterus, skin of the labia majora (in women); scrotal skin; testicular membranes; levator testis muscle (in men)
Lateral cutaneous nerve of the thigh	Skin of the posterolateral thigh, lateral thigh to the knee joint
Obturator nerve	Hip capsule, skin of the lower half of the medial thigh, obturator externus, adductors of the thigh, gracilis and pectineus muscles
Femoral nerve	Muscles: quadriceps femoris, sartorius, pectineus. Skin of the anteromedial surface of the thigh, skin in the area of ​​the knee joint, anteromedial surface of the leg, dorsum and medial edge of the foot to the big toe

Nerves of the sacral plexus

	Innervated area
Obturator internal nerve	Muscles: obturator internus, gemellus superior and inferior, piriformis, quadratus femoris
Pear-shaped
Nerve of the quadratus femoris muscle
Superior gluteal nerve	Muscles: gluteus medius and minimus, tensor fascia lata
Inferior gluteal nerve	Gluteus maximus muscle; hip capsule
Pudendal nerve	Muscles: external anal sphincter, levator ani, ischiocavernosus, bulbospongiosus, superficial and deep transverse perineal muscles, urethral sphincter; Skin of the perineum around the anus; the posterior surface of the scrotum in men (labia majora in women), the back and head of the penis (clitoris in women), cavernous bodies, glans penis (clitoris in women)
Posterior cutaneous nerve of the thigh	Skin of the gluteal region, perineum, posterior thigh, including the popliteal fossa
Sciatic nerve	Muscles: semimembranosus and tendon, biceps femoris (long head), posterior adductor magnus
tibial	Knee and ankle joints; skin of the posteromedial surface of the leg, heel. Muscles: gastrocnemius, soleus, plantaris, popliteus, flexor toe longus, tibialis posterior, flexor hallucis longus
Medial plantar	The skin of the medial edge of the foot, the big toe and the sides of the I-IV toes facing each other, the joints of the foot.
	Muscles: flexor digitorum brevis, medial head of flexor hallucis brevis, abductor hallucis, I-II lumbricals
Lateral plantar	Skin of the sole, plantar surface and lateral side of the fifth toe, sides of the IV-V toes facing each other, joints of the foot. Muscles: quadratus plantae, lateral head of the flexor hallucis brevis, abductor of the little toe, flexor of the little toe brevis, adductor of the big toe, III-IV lumbrical, plantar and dorsal interosseous
Common peroneal nerve	Knee joint capsule, short head of the biceps femoris muscle; skin of the lateral surface of the leg and groans

Spinal nerves (nervus spinalis).

Spinal nerves are paired, metamerically located nerve trunks. A person has 31 pairs of spinal nerves, corresponding to 31 pairs of spinal cord segments: 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and a pair of coccygeal nerves. Each spinal nerve corresponds in origin to a specific segment of the body, i.e. innervates the area of ​​skin, muscle and bone that developed from this somite. The spinal cord segments are combined into 5 sections.

Cervical - 7 vertebrae, 8 nerves. The first cervical nerve exits between the brain and the first cervical vertebra, so there are 8 nerves and 7 vertebrae.

Thoracic - 12 vertebrae, 12 nerves.

Lumbar - 5 vertebrae, 5 nerves.

Sacral - 5 vertebrae, 5 nerves.

Coccygeal - 1 segment, 1 pair of nerves.

Cauda equina - horse tail. It is formed by the roots of the lower spinal nerves, which elongate in length to reach their corresponding intervertebral foramina.

Each spinal nerve is formed by the union of the anterior and dorsal roots immediately lateral to the spinal ganglion at the intervertebral foramen through which the nerve exits the spine.

The nerve immediately divides into 4 branches:

1) spinal or dorsal (Ramus dorsalis) - consists of sensory and motor fibers and innervates the skin and muscles of the dorsal part of the corresponding segment

2) ventral or anterior (Ramus ventralis) - consists of sensory and motor fibers and innervates the skin and muscles of the abdominal part of the body

3) connective (Ramus communicance) - consists of autonomic fibers that are separated from all the others and go to the autonomic ganglia.

4) meningeal (Ramus meningius) - consists of autonomic and sensory fibers that return to the spinal canal and innervate the membranes of the corresponding segment of the brain.

Each spinal nerve begins from the spinal cord with two roots: anterior and posterior. The anterior root is formed by the axons of motor neurons, the bodies of which are located in the anterior horns of the spinal cord. The dorsal root (sensitive), is formed by the central processes of pseudounipolar (sensitive) cells ending on the cells of the dorsal horns of the spinal cord or heading to the sensory nuclei of the medulla oblongata. Peripheral processes of pseudounipolar cells as part of spinal nerves are directed to the periphery, where their end sensory devices - receptors - are located in organs and tissues. The bodies of pseudounipolar sensory cells are located in the spinal (sensitive) ganglion adjacent to the dorsal root and forming its extension.

Formed by the fusion of the posterior and anterior roots, the spinal nerve emerges from the intervertebral foramen and contains both sensory and motor nerve fibers. The anterior roots emerging from the 8th cervical, all thoracic and upper two lumbar segments also contain autonomic (sympathetic) nerve fibers coming from the cells of the lateral horns of the spinal cord. The spinal nerves, emerging from the intervertebral foramen, are divided into three or four branches: the anterior branch, the posterior branch, the meningeal branch, the white communicating branch, which arises only from the 8th cervical, all thoracic and the upper two lumbar spinal nerves.

The anterior and posterior branches of the spinal nerves, except for the posterior branch of the 1st cervical nerve, are mixed branches (have motor and sensory fibers), innervate both the skin (sensory innervation) and skeletal muscles (motor innervation). The posterior branch of the 1st cervical spinal nerve contains only motor fibers. The meningeal branches innervate the membranes of the spinal cord, and the white communicating branches contain preganglionic sympathetic fibers going to the nodes of the sympathetic trunk. All spinal nerves are approached by connecting branches (gray), consisting of postganglionic nerve fibers coming from all nodes of the sympathetic trunk. As part of spinal nerves, postganglionic sympathetic nerve fibers are directed to the vessels, glands, muscles that raise the hair, striated muscle and other tissues to ensure their functions, including metabolism (trophic innervation).

Innervation of the limbs.

The limbs are formed in ontogenesis as derivatives of the ventral part of the body => they are innervated only by the ventral branches of the spinal nerves. During ontogenesis, the limbs lose traces of their segmental origin, therefore the ventral branches running from them form plexuses. Plexuses are nerve networks in which the ventral branches of the spinal nerves exchange their fibers and, as a result, nerves emerge from the plexuses, each of which contains fibers from different segments of the spinal cord. There are 3 plexuses:

1) cervical - formed by the ventral branches of 1-4 pairs of cervical nerves, lies next to the cervical vertebra and innervates the neck

2) brachial - formed by the ventral branches of nerves 5 cervical - 1 thoracic, lies in the region of the clavicle and axilla, innervates the arms

3) lumbosacral - formed by 12 thoracic - 1 coccygeal, lies next to the lumbar and sacral vertebrae, innervates the legs.

Each nerve is made up of nerve fibers. Sensory nerves are formed by processes of neurons of the sensory ganglia of cranial nerves or spinal nerves. Motor nerves consist of processes of nerve cells lying in the motor nuclei of the cranial nerves or in the nuclei of the anterior trunks of the spinal cord. Autonomic nerves are formed by processes of cells of the autonomic nuclei of the cranial nerves or the lateral trunks of the spinal cord. All dorsal roots of the spinal nerves are afferent, while the anterior roots are efferent.

Reflex arc

The spinal cord performs two important functions: reflex And conductor.

Reflex arc- this is a chain of neurons that ensure the transmission of excitation from receptors to working organs. It starts with receptors.

Receptor- this is the final branching of the nerve fiber, which serves to perceive irritation. Receptors are always formed by processes of neurons lying outside the brain, in sensory ganglia. Typically, auxiliary structures take part in the formation of receptors: epithelial and connective tissue elements and structures.

There are three types of receptors:

Extrareceptors– perceive irritation from the outside. These are the sense organs.

Introreceptors– perceive irritation from the internal environment. These are receptors of internal organs.

Proprioceptors– receptors of muscles, tendons, joints. They signal the position of the body in space.

There are simple receptors (pain receptors, for example, are simply nerve endings) and very complex ones (the organ of vision, hearing, and so on), and there are also many auxiliary structures.

The first neuron of the reflex arc is a sensory neuron spinal ganglion.

The spinal ganglion is a collection of nerve cells in the dorsal roots of the spinal nerves in the intervertebral foramen.

Cells of the dorsal ganglion - pseudounipolar. Each such cell has one process, which very quickly divides in a T-shape into two - peripheral and central processes.

Peripheral processes go to the periphery of the body and form receptors there with their terminal branches. The central processes lead to the spinal cord.

In the simplest case, the central process of the dorsal ganglion cell, having entered the spinal cord, forms a synapse directly with motor and vegetative cells, either with the motor neuron of the anterior horn of the gray part of the spinal cord, or with the autonomic neuron of the lateral horn. The axons of these neurons leave the spinal cord as part of the ventral root (radis ventralis) of the spinal nerves and go to the effectors. The motor axon goes to the striated muscles, and the autonomic axon goes to the autonomic ganglion. From the autonomic ganglion, fibers are sent to the glands and smooth muscles of the internal organs.

Thus, glands, smooth muscles and striated muscles are the effectors that are responsible for irritation.

A response to the same irritation is possible from both motor and autonomic centers. For example, the tendon knee reflex. But even in the simplest reactions, not one segment of the spinal cord is involved, but several, and, most often, the brain, so it is necessary that the impulse propagate throughout the spinal cord and reach the brain. This is done with the help of intercalary cells (interneurons) of the dorsal horns of the gray matter of the spinal cord.

Typically, a dorsal horn switch neuron is inserted between the sensory neuron of the spinal ganglion and the motor neuron of the anterior horn of the gray matter of the spinal cord. The central process of the dorsal ganglion cell synapses with the intercalary cell. The axon of this cell emerges and divides in a T-shape into ascending and descending processes. From these processes, lateral processes (collaterals) extend to different segments of the spinal cord and form synapses with motor and autonomic nerves. This is how the impulse spreads along the spinal cord.

The axons of switching neurons go to other segments of the spinal cord, where they synapse with motor neurons, as well as the switching nuclei of the brain. The axons of switching neurons form their own bundles of the spinal cord and most of the ascending pathways. Therefore it is customary to talk about reflex ring, since effectors contain receptors that constantly send impulses to the central nervous system.

There are also intercalary cells in the anterior horns. They distribute the impulse to various motor neurons. Thus, the entire variety of connections in the brain is provided by intercalary cells, or, in other words, switching neurons of the gray matter of the spinal cord.

Nervous tissue

Macrostructure of nervous tissue

Nervous tissue

glia neuron

body, dendrites axon

(to perceive a nerve impulse) (to transmit a nerve impulse to others

neurons or working organs)

The basic structural and functional unit of nervous tissue is the neuron (from the Greek Neiron - nerve), i.e. a nerve cell with a high level of differentiation.

The first mention of a nerve cell dates back to 1838 and is associated with the name of Remarque. Later, the German anatomist Otto Deiters in 1865, in his studies of the human brain and spinal cord, using the isolation method, found that of the numerous processes extending from the body of the nerve cell, one always proceeds without dividing, while others divide repeatedly.

Deiters called the non-dividing process “nervous” or “axial-cylindrical”, and the dividing ones – “protoplasmic”. This is how Deiters was able to distinguish between what we now call axons and dendrites.

At the end of the 19th century, extremely effective histological methods were developed, thanks to which it became possible to see the entire nerve cell, as if it had been isolated from the central nervous system. Studying preparations prepared using the Golgi method, the Spanish scientist Santiago Ramon y Cajal in 1909-1911. laid the foundations for the modern understanding of the structure of the nervous system. He proved that nerve cells are structurally separate trophic and functional units, and the entire nervous system is built on similar nerve units. To designate these cellular units, the German anatomist Baron Wilhelm von Waldeyer introduced the term “neuron” into scientific use in 1891, and the doctrine of the cellular structure of the nervous system was called the “neuron theory”.

Nerve cells are the main material of the brain. So elementary units in anatomical, genetic and functional terms, neurons have the same genes, general structure and the same biochemical apparatus as other cells, but at the same time they have functions completely different from the functions of other cells.

The most important features of neurons are:

Their characteristic shape

The ability of the outer membrane to generate nerve impulses

The presence of a special unique structure of synapses that serve to transmit information from one neuron to another or to a working organ

There are more than 10 to 12 neurons in the human brain, but no two neurons are identical in appearance. The smallest neurons are found in the cerebellar cortex. Their diameter is 4-6 microns. The largest neurons are Betz's giant pyramidal cells, reaching 110-150 microns in diameter. The second largest cells are Purkinje cells, which are also found in the cerebellar cortex.

There are 31 pairs of spinal nerves: 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and 1 pair of coccygeal. All of them are mixed in function. Each nerve is formed by connecting two roots: anterior - motor and posterior - sensitive. The roots unite at the intervertebral foramen. The spinal nerve divides as it exits the intervertebral foramen into two branches: front And rear(Fig. 139), both of them are mixed in function. In addition, from each spinal nerve there is a branch to the meninges of the spinal cord (meningeal branch), and from the thoracic and two to three upper lumbar nerves there is also a connecting branch to the sympathetic trunk (see Autonomic nervous system).

Posterior branches spinal nerves innervate the deep back muscles and skin in the spinal region.

Anterior branches Spinal nerves intertwine with each other to form nerve plexuses. There are plexuses: cervical, brachial, lumbar and sacral. From each plexus several branches emerge - nerves that go to certain muscles and areas of the skin. The anterior branches of the thoracic nerves do not form a plexus.

Cervical plexus(plexus cervicales) is formed by the anterior branches of the four upper cervical nerves, located in the neck behind the sternocleidomastoid muscle. The following branches extend from this plexus (Fig. 140).

Transverse cervical nerve, innervating the skin of the neck.

Greater auricular nerve, innervating the skin near the auricle.

Lesser occipital nerve, innervating the skin of the occipital region (partially).

Supraclavicular nerves, innervating the skin of the supraclavicular and subclavian region.

Phrenic nerve(n. phrenicus) 1 descends from the neck into the chest cavity, innervates the diaphragm and partially the pleura and pericardium. Branches also extend from the cervical plexus to the deep muscles of the neck.

1 (Abbreviated as nervus (nerve) - n., nervi (nerves) - nn.)

Brachial plexus(plexus brachialis) is formed by the anterior branches of the four lower cervical nerves and partly by the anterior branch of the first thoracic nerve. On the neck, this plexus passes through the interscalene space, from where it passes into the axillary cavity.

In the neck area (above the collarbone), the brachial plexus gives off so-called short branches. They innervate the muscles: pectoralis major and minor; serratus anterior, vastus dorsi, subscapularis, supraspinatus and infraspinatus, rhomboids and levator scapulae.

In other words, the short branches of the brachial plexus innervate the muscles that move the shoulder girdle.

In the axillary cavity (below the clavicle), long branches depart from the brachial plexus, innervating the upper limb (Fig. 141). These include:

1. Cutaneous medial nerve of the shoulder innervates the skin of the shoulder from the inside.

2. Cutaneous medial nerve of the forearm innervates the skin of the anterior inner side of the forearm.

3. Musculocutaneous nerve innervates the anterior muscles of the shoulder and the skin of the anterior side of the forearm.

4. Median nerve(n. medianus) does not give off branches on the shoulder; on the forearm it innervates all the anterior muscles, with the exception of the flexor carpi ulnaris and part of the deep flexor digitorum. From the forearm, the median nerve passes to the palmar side of the hand, where it innervates the muscles of the eminence of the thumb, two lumbrical muscles and the skin of 3 1/2 fingers, starting with the thumb.

5. Radial nerve(n. radialis) innervates the triceps muscle and skin of the posterior surface on the shoulder, the posterior muscles and skin of the posterior surface on the forearm, and the skin of the dorsal surface of 2 1/2 fingers, starting with the thumb, on the hand.

6. Ulnar nerve(n. ulnaris) does not give branches on the shoulder; on the forearm it innervates the flexor carpi ulnaris and part of the deep flexor digitorum. In the lower part of the forearm, the nerve is divided into two branches, which pass to the hand, where they innervate: one branch - the skin of the dorsal surface of 2 1/2 fingers, starting with the little finger, the other - the muscles of the eminence of the fifth finger, all interosseous and two lumbrical muscles, as well as skin of the palmar surface of 1 1/2 fingers, starting with the little finger. It should be borne in mind that the ulnar nerve, when passing from the shoulder to the forearm, is located superficially in the groove between the medial epicondyle of the humerus and the olecranon process of the ulna and can be easily injured in this place.

Axillary nerve(n. axillaris) is a relatively short branch that innervates the deltoid muscle, the skin over it and the shoulder joint bursa.

Anterior branches of the thoracic nerves, as noted, do not form plexuses. They are called intercostal nerves (nn. intercostales), pass between the ribs and innervate the intercostal muscles, chest skin and pleura. The lower intercostal nerves are also involved in the innervation of the muscles and skin of the anterior abdominal wall.

Lumbar plexus(plexus lumbalis) is formed by the anterior branches of the upper three lumbar and partially by the anterior branch of the XII thoracic and IV lumbar nerves, located behind and in the thickness of the psoas major muscle.

The branches of this plexus innervate the skin and muscles of the lower abdominal wall, the psoas and iliacus muscles, the anterior and medial muscle groups of the thigh and the skin above them, as well as the skin of the medial surface of the leg.

The largest branches of the lumbar plexus are the following (Fig. 142).

Femoral nerve(n. femoralis). It passes under the inguinal ligament to the anterior surface of the thigh, where it innervates the quadriceps and sartorius muscles and the skin above them. In addition, the internal cutaneous nerve of the lower limb (n. saphenus), which innervates the skin of the medial surface of the leg, departs from the femoral nerve.

Obturator nerve(n. obturatorius) passes to the thigh through the canal of the same name. On the thigh, it innervates the medial (adductor) muscles and the skin over them.

Iliohypogastric nerve goes to the muscles and skin of the lower abdominal wall.

Sacral plexus(plexus sacralis) is formed by the anterior branches of the IV (partial) and V lumbar nerves, all sacral and coccygeal nerves. It is located in the pelvic cavity on the piriformis muscle.

The branches of this plexus innervate all the muscles of the pelvis, with the exception of the iliopsoas, the muscles and skin of the perineum, the posterior muscles of the thigh and the skin above them, all the muscles and skin of the lower leg and foot, with the exception of the skin of the medial surface of the lower leg. The largest branch of the sacral plexus (and in general the largest nerve in the human body) is sciatic nerve(n. ischiadicus). This nerve exits the pelvic cavity to the posterior surface of the thigh (Fig. 143), where it innervates the semitendinosus, semimembranosus and biceps muscles. Usually in the upper corner of the popliteal there are two branches - tibial nerve and common peroneal nerve.

The tibial nerve with its branches innervates the posterior muscles of the leg and the skin above them, the muscles and skin of the plantar side of the foot.

The common peroneal nerve is in turn divided into the deep and superficial peroneal nerves. The first of them innervates the anterior muscles of the leg and the muscles of the dorsum of the foot, the second - the external muscles of the leg and the skin of the dorsum of the foot.

Spinal nerves arise from the spinal cord in 31 pairs. Each spinal nerve is formed from the fusion of the posterior, or dorsal, sensory root and the anterior, or ventral, motor root. The mixed nerve thus formed exits the spinal canal through the intervertebral foramen. According to the segments of the spinal cord, the spinal nerves are divided into 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and 1 pair of coccygeal. Each of them, emerging from the intervertebral foramen, is divided into four branches: 1) the meningeal branch, which goes into the spinal canal and innervates the membranes of the spinal cord; 2) connective, which connects the spinal nerve with the nodes of the sympathetic trunk located along the spinal column (see section “Autonomic nervous system”); 3) back and 4) front. The posterior branches of the spinal nerves go backward and innervate the skin of the neck, back and part of the gluteal region, as well as the proper back muscles. The anterior branches, moving forward, innervate the skin and muscles of the chest and abdomen, as well as the skin and muscles of the limbs. The anterior branches, with the exception of the thoracic ones, connect with each other and form the following plexuses: cervical, brachial, lumbosacral, divided into lumbar and sacral. The anterior branches of the thoracic nerves do not connect with each other, do not form plexuses and are called intercostal nerves.

The study of spinal nerves is of particular interest to athletes. During massage, one should take into account not only the course of blood vessels, but also the location of nerve trunks. Nerve injuries are usually accompanied by changes in the function of certain muscle groups. Knowledge of their innervation can help in selecting sets of therapeutic gymnastic exercises necessary to restore function.

Cervical plexus formed by the connection of the anterior branches of the four upper cervical spinal nerves and is located under the sternocleidomastoid muscle. Sensitive branches of the plexus emerge from under the middle of the posterior edge of the sternocleidomastoid muscle and innervate the skin in the back of the head, auricle and neck. The motor branches go to the muscles of the neck. The largest branch of the cervical plexus is the mixed phrenic nerve. It gives sensory branches to the pleura and pericardial sac, and motor branches to the diaphragm.

Brachial plexus formed mainly by the connection of the anterior branches of the four lower cervical spinal nerves. It is located between the anterior and middle scalene muscles and has supra- and subclavian parts. The branches extending from the plexus are divided into short and long. The short ones innervate the muscles attached to the scapula and surrounding the shoulder joint, and the long ones go down along the upper limb and innervate its skin and muscles. The main long branches are: the musculocutaneous nerve, median, ulnar and radial.

Musculocutaneous nerve pierces the coracobrachialis muscle and goes between the biceps brachii and the brachialis muscle. It gives branches to all these muscles, as well as to the humerus and elbow joint. Continuing on the forearm, it innervates the skin of its outer surface.

Median nerve runs on the shoulder, along the medial groove of the shoulder, together with the brachial artery, without giving branches. On the forearm, it is located between the superficial and deep flexor digitorum muscles, innervating all flexors of the hand and fingers (with the exception of the flexor carpi ulnaris and part of the deep flexor digitorum muscle), the pronator quadratus muscle, the bones of the forearm and the radiocarpal joint. Next, the median nerve passes to the hand, where it innervates a group of muscles of the thumb (except for the adductor pollicis muscle), the 1st and 2nd lumbrical muscles and the skin of three and a half fingers, starting from the thumb.

Ulnar nerve runs on the shoulder in the same way as the median one, along the medial groove of the shoulder, then goes around the inner epicondyle of the humerus and passes to the forearm, into the ulnar groove, lying together with the ulnar artery. On the forearm, it innervates those muscles that the middle nerve does not innervate - the flexor carpi ulnaris and partially the deep flexor digitorum. In the lower part of the forearm, the ulnar nerve divides into dorsal and palmar branches. The dorsal branch innervates the skin of two and a half fingers on the dorsal surface, counting from the little finger, and the palmar branch innervates the muscle group of the little finger, the adductor pollicis muscle, all interosseous muscles, the 3rd and 4th lumbrical muscles and the skin of one and a half fingers on the palmar surface, starting from the little finger.

Radial nerve on the shoulder it runs spirally between the humerus and the triceps muscle, which it innervates. In the cubital fossa, the nerve is divided into deep and superficial branches. The deep side branch innervates all the muscles of the posterior surface of the forearm. The superficial branch runs in place with the radial artery along the radial groove, passes to the dorsum of the hand and innervates the skin of two and a half fingers, counting from the thumb.

The anterior branches of the thoracic nerves (12 pairs) are called intercostal nerves. They do not form plexuses, pass along the lower edge of the ribs and innervate the intercostal muscles and chest. The 6 lower pairs, going down, take part in the innervation of the skin and abdominal muscles.

Lumbar plexus formed by the connection of the anterior branches of the three and partially fourth lumbar spinal nerves. The lumbar plexus is located in front of the transverse processes of the vertebrae, in the thickness of the psoas major muscle. Most of the branches emerge from under the outer edge of this muscle and innervate the iliopsoas muscle, quadratus lumborum muscle, internal oblique and transverse abdominal muscles, as well as the skin of the external genitalia. Of the major branches descending to the thigh, the largest are the lateral femoral cutaneous nerve, the femoral nerve, and the obturator nerve.

exits the thigh in the area of ​​the superior anterior iliac spine and innervates the skin of the outer surface of the thigh.

Femoral nerve comes out from under the outer edge of the psoas major muscle, passes along with the iliopsoas muscle under the inguinal ligament and, emerging on the thigh, gives branches to the sartorius, pectineus muscles and quadriceps femoris muscle. Cutaneous branches innervate the skin of the anterior thigh. The longest of them - the hidden nerve - descends on the inner surface of the leg and foot, reaches the big toe and innervates the skin of these areas. If the femoral nerve is damaged, it is impossible to bend the torso, thigh and straighten the lower leg.

Obturator nerve comes out from under the internal psoas major muscle, passes through the obturator canal to the thigh and innervates the hip-femoral joint, all the adductor muscles and skin of the inner surface of the thigh. Nerve injuries due to | lead to dysfunction of the adductor muscles of the thigh.

Sacral plexus formed by the connection of the anterior branches of the last one and a half or two lower lumbar and three to four upper sacral spinal nerves. It is located in the pelvic cavity, on the anterior surface of the sacrum and piriformis muscle. The branches extending from the plexus are divided into short and long. The short ones innervate the muscles in the pelvic area - the piriformis, internal obturator, twin muscles, quadratus lumborum and pelvic floor muscles. Of the short branches, the superior gluteal nerve and the inferior gluteal nerve, which innervate the gluteal muscles, are the most important. The long branches include two nerves: the posterior cutaneous nerve of the thigh and the sciatic nerve.

Posterior cutaneous nerve of the thigh exits the thigh in the area of ​​the gluteal fold and innervates the skin of the posterior surface of the thigh. The sciatic nerve is one of the largest nerves in the human body. It exits the pelvic cavity through the greater sciatic foramen, below the piriformis muscle, goes under the gluteus maximus muscle, emerges from under its lower edge onto the back of the thigh and innervates the muscles located there. In the popliteal fossa (and sometimes higher), the nerve divides into the tibial nerve and the common peroneal nerve.

Tibial nerve goes to the lower leg between the soleus muscle and the posterior tibial muscle, goes around the inner malleolus and goes to the plantar surface of the foot. On the lower leg it innervates all the muscles and skin of the posterior surface, and on the foot it innervates the skin and muscles of the sole.

The common peroneal nerve in the region of the head of the fibula is divided into two nerves: the deep peroneal nerve and the superficial peroneal nerve.

The deep peroneal nerve runs along the anterior surface of the leg, between the tibialis anterior muscle and the extensor pollicis longus muscle, together with the anterior tibial artery, and passes to the dorsum of the foot. On the lower leg it innervates the extensor muscles of the foot, and on the foot it innervates the extensor digitorum brevis and the skin between the 1st and 2nd toes. The superficial peroneal nerve supplies the long and short peroneal muscles with branches, then in the lower third of the leg it exits under the skin and descends to the dorsum of the foot, where it innervates the skin of the fingers.

When the sciatic nerve is damaged, flexion of the lower leg becomes impossible, and when the common peroneal nerve is damaged, a very peculiar gait appears, called in medicine “cock’s gait,” in which a person first places the foot on the toe, then on the outer edge of the foot, and only then on the heel. In sports practice, diseases of the sciatic nerve are quite common - inflammatory processes (associated with infection or hypothermia) and sprains (when performing stretching exercises, for example, when doing splits, when swinging a straight leg during a jump, etc.).

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SEE MORE:

1. Characteristics of the nervous system and its functions.

2. Structure of the spinal cord.

3. Functions of the spinal cord.

4. Overview of the spinal nerves. Nerves of the cervical, brachial, lumbar and sacral plexuses.

OBJECTIVE: To know the general structure of the nervous system, topography, structure and functions of the spinal cord, spinal roots and branches of the spinal nerves.

Introduce the reflex principle of the nervous system and the innervation zone of the cervical, brachial, lumbar and sacral plexuses.

Be able to show spinal cord neurons, pathways, spinal roots, nodes and nerves on posters and tablets.

The nervous system is one of the most important systems that ensures the coordination of processes occurring in the body and the establishment of relationships between the body and the external environment. The study of the nervous system - neurology.

The main functions of the nervous system include:

1) perception of stimuli acting on the body;

2) conducting and processing perceived information;

3) the formation of response and adaptive reactions, including higher nervous activity and the psyche.

According to topographical principles, the nervous system is divided into central and peripheral.

The central nervous system (CNS) includes the spinal cord and brain, the peripheral nervous system includes everything that is outside the spinal cord and brain: spinal and cranial nerves with their roots, their branches, nerve endings and ganglia (nerve nodes) formed by the bodies neurons. The nervous system is conventionally divided into somatic (regulation of relationships between the body and the external environment), and vegetative (autonomous) (regulation of relationships and processes within the body).

The structural and functional unit of the nervous system is the nerve cell - neuron (neurocyte). A neuron has a cell body - a trophic center and processes: dendrites, through which impulses travel to the cell body, and an axon,

through which impulses travel from the cell body. Depending on quantity

processes, there are 3 types of neurons: pseudounipolar, bipolar and multipolar. All neurons are connected to each other through synapses.

One axon can form up to 10,000 synapses on many nerve cells. There are about 20 billion neurons and about 20 billion synapses in the human body.

Based on their morphofunctional characteristics, there are 3 main types of neurons.

1) Afferent (sensitive, receptor) neurons conduct impulses to the central nervous system, i.e.

centripetal. The bodies of these neurons always lie outside the brain or spinal cord in the nodes (ganglia) of the peripheral nervous system.

2) Intercalary (intermediate, associative) neurons transmit excitation from the afferent (sensitive) neuron to the efferent (motor or secretory).

3) Efferent (motor, secretory, effector) neurons conduct impulses along their axons to the working organs (muscles, glands).

The bodies of these neurons are located in the central nervous system or on the periphery - in the sympathetic and parasympathetic nodes.

The main form of nervous activity is the reflex. Reflex (Latin reflexus - reflection) is a causally determined reaction of the body to irritation, carried out with the obligatory participation of the central nervous system. The structural basis of reflex activity is made up of neural chains of receptor, intercalary and effector neurons. They form a path along which nerve impulses travel from receptors to an executive organ called a reflex arc.

It consists of: receptor -> afferent nerve pathway -> reflex center -> efferent pathway -> effector.

2. The spinal cord (medulla spinalis) is the initial part of the central nervous system. It is located in the spinal canal and is a cylindrical cord, flattened from front to back, 40-45 cm long, 1 to 1.5 cm wide, weighing 34-38 g (2% of the brain mass).

At the top it passes into the medulla oblongata, and at the bottom it ends with a point - the conus medullaris at the level of the I - II lumbar vertebrae, where a thin terminal (end) branches off from it.

filament (rudiment of the caudal (tail) end of the spinal cord). The diameter of the spinal cord varies in different areas.

In the cervical and lumbar regions it forms thickenings (innervation of the upper and lower extremities). On the anterior surface of the spinal cord there is an anterior median fissure, on the posterior surface there is a posterior median sulcus; they divide the spinal cord into interconnected right and left symmetrical halves. On each half, weakly defined anterior lateral and posterior lateral grooves are distinguished. The first is the place where the anterior motor roots exit the spinal cord, the second is the place where the posterior sensory roots of the spinal nerves enter the brain.

These lateral grooves also serve as the boundary between the anterior, lateral and posterior cords of the spinal cord. Inside the spinal cord there is a narrow cavity - the central canal, filled with cerebrospinal fluid (in an adult, it is overgrown in various parts, and sometimes throughout the entire length).

The spinal cord is divided into parts: cervical, thoracic, lumbar, sacral and coccygeal, and the parts are divided into segments.

A segment (structural and functional unit of the spinal cord) is the area corresponding to two pairs of roots (two anterior and two posterior).

Throughout the entire length of the spinal cord, 31 pairs of roots emerge from each side. Accordingly, 31 pairs of spinal nerves in the spinal cord are divided into 31 segments: 8 cervical,

12 thoracic, 5 lumbar, 5 sacral and 1-3 coccygeal.

The spinal cord consists of gray and white matter. Gray matter - neurons (about 13 million) forming in each half of the spinal cord

3 gray pillars: front, rear and side.

In a cross section of the spinal cord, the columns of gray matter on each side have the appearance of horns. There is a wider anterior horn and a narrow posterior horn, corresponding to the anterior and posterior gray columns. The lateral horn corresponds to the intermediate column (vegetative) of gray matter. The gray matter of the anterior horns contains motor neurons (motoneurons), the posterior horns contain intercalary sensory neurons, and the lateral horns contain intercalary autonomic neurons.

The white matter of the spinal cord is localized outward from the gray matter and forms the anterior, lateral and posterior cords. It consists predominantly of longitudinally running nerve fibers, united in bundles - pathways.

The white matter of the anterior cords contains descending pathways, the lateral cords contain ascending and descending tracts, and the posterior cords contain ascending pathways.

The connection between the spinal cord and the periphery is carried out through

nerve fibers passing through the spinal roots. Front

tristimulus sensory fibers (therefore, with bilateral transection of the dorsal roots of the spinal cord in a dog, sensitivity disappears, and of the anterior roots, sensitivity is preserved, but the tone of the muscles of the limbs disappears).

The spinal cord is covered by three meninges: the inner -

soft (vascular), middle - arachnoid and outer - hard.

the hard shell and periosteum of the spinal canal have an epidural space, between the hard shell and the arachnoid there is a subdural space. The arachnoid membrane is separated from the soft (vascular) shell by the subarachnoid (subarachnoid) space, containing cerebrospinal fluid (100-200 ml, performs trophic and protective functions)

3. The spinal cord performs two functions: reflex and conductive.

The reflex function is carried out by the nerve centers of the spinal cord, which are the segmental working centers of unconditioned reflexes.

Their neurons are directly connected to receptors and working organs. Each segment of the spinal cord, through its roots, innervates three metameres (transverse segments) of the body and receives sensitive information also from three metameres. Due to this overlap, each metamer of the body is innervated by three segments and transmits signals (impulses) to three segments of the spinal cord (safety factor). The spinal cord receives afferentation from receptors of the skin, motor apparatus, blood vessels, digestive

body tract, excretory and genital organs.

Efferent impulses from the spinal cord go to the skeletal muscles, including the respiratory muscles - intercostal muscles and the diaphragm, internal organs, blood vessels, sweat glands, etc.

The conductive function of the spinal cord is carried out through ascending and descending pathways. Upstream paths transmit

information from tactile, pain, temperature receptors of the skin and

proprioceptors of skeletal muscles through neurons of the spinal cord and

other parts of the central nervous system to the cerebellum and cerebral cortex. Descending pathways connect the cerebral cortex, subcortical nuclei and brainstem formations with motor neurons of the spinal cord.

They provide the influence of the higher parts of the central nervous system on the activity of skeletal muscles.

4. A person has 31 pairs of spinal nerves, corresponding to 31 segments of the spinal cord: 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and a pair of coccygeal nerves.

Each spinal nerve is formed by connecting the anterior (motor) and posterior (sensory) roots. Upon exiting the intervertebral foramen, the nerve divides into

two main branches: anterior and posterior, both mixed in function.

Through the spinal nerves, the spinal cord carries out

the following innervation: sensitive - the trunk, limbs and part of the neck, motor - all muscles of the trunk, limbs and part of the neck muscles; sympathetic innervation - of all organs that have it, and parasympathetic - of the pelvic organs.

The posterior branches of all spinal nerves have a segmental arrangement.

They go to the back surface of the body, where they are divided into

cutaneous and muscle branches that innervate the skin and muscles of the back of the head,

neck, back, lumbar region and pelvis.

Spinal cord

These branches are named according to

existing nerves (for example, the posterior branch of the I thoracic nerve, ... II, etc.).

The anterior branches are much thicker than the posterior ones, of which there are only 12 pairs

thoracic spinal nerves have a segmental (metameric) distribution

position.

These nerves are called intercostal nerves because they go between the

ber spaces on the inner surface along the lower edge of the corresponding rib.

They innervate the skin and muscles of the anterior and lateral walls of the chest and abdomen. The anterior branches of the remaining spinal nerves form plexuses before going to the corresponding area of ​​the body.

There are cervical, brachial, lumbar and sacral plexuses.

Nerves extend from the plexuses, each of which has its own name and innervates a specific area.

The cervical plexus is formed by the anterior branches of the four superior

cervical nerves. It is located in the area of ​​the four upper cervical vertebrae on the deep muscles of the neck. Sensory (cutaneous), motor (muscular) and mixed nerves (branches) depart from this plexus.

1) Sensory nerves: lesser occipital nerve, greater auricular

nerve, transverse nerve of the neck, supraclavicular nerves.

2) The muscle branches innervate the deep muscles of the neck, as well as the trapezius, sternocleidomastoid muscles.

3) The phrenic nerve is a mixed nerve and the largest nerve of the cervical plexus; its motor fibers innervate the diaphragm, and its sensory fibers innervate the pericardium and pleura.

The brachial plexus is formed by the anterior branches of the four lower cervical, part of the anterior branch of the IV cervical and I thoracic spinal cords

In the plexus, there are supraclavicular (short) branches (innervate the muscles and skin of the chest, all muscles of the shoulder girdle and back muscles) and subclavian (long) branches (innervate the skin and muscles of the free upper limb).

The lumbar plexus is formed by the anterior branches of the upper three lumbar nerves and partly by the anterior branches of the XII thoracic and IV lumbar nerves.

Short branches of the lumbar plexus innervate the quadratus lumborum muscle, the iliopsoas muscle, the abdominal muscles, as well as the skin of the lower abdominal wall and external genitalia.

The long branches of this plexus innervate the free lower limb

The sacral plexus is formed by the anterior branches of IV (partially)

and the V lumbar nerves and the upper four sacral nerves. The short branches include the superior and inferior gluteal nerves, the pudendal nerve, the obturator internus, the piriformis nerve, and the quadratus femoris nerve.

The long branches of the sacral plexus are represented by the posterior cutaneous

femoral nerve and sciatic nerve.

Inflammation of the nerve is called neuritis (mononeuritis), roots

brain - radiculitis (lat.

radix - root), nerve plexus - plexitis

(Latin plexus - plexus). Multiple inflammation or degenerative

nerve damage is polyneuritis. Pain along the nerve, not accompanied by a significant impairment of the function of the organ or muscle, is called neuralgia. Burning pain that intensifies in attacks is called causalgia (Greek.

kausis - burning, algos - pain), observed after damage (wound, burn) to nerve trunks rich in fibers of the sympathetic nervous system. Pain that acutely occurs in the lumbar region during physical exertion, especially lifting weights, is called lumbago (lumbago).

Date of publication: 2014-11-26; Read: 159 | Page copyright infringement

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Spinal nerves

Rice.

996. Spinal nerves, nn. spinales; front view (diagram). Rice. 995. Spinal cord segment (semi-schematic). Rice.

997. Projection of spinal roots and nerves onto the spinal column (diagram).

Spinal nerves, nn. spinales(rice.

995, 996, 997), are paired (31 pairs), metamerically located nerve trunks:

1. Cervical nerves, nn.

   cervicales (CI–CVII), 8 pairs

2. Thoracic nerves, nn. thoracici (ThI–ThXII), 12 pairs
3. Lumbar nerves, nn. lumbales (LI–LV), 5 pairs
4. Sacral nerves, nn. sacrales (SI–SV), 5 pairs
5. Coccygeal nerve, n. coccygeus (CoI–CoII), 1 pair, rarely two.

The spinal nerve is mixed and is formed by the fusion of two roots belonging to it:

1) dorsal root [sensitive], radix dorsalis, and

2) anterior root [motor], radix ventralis.

Each root is connected to the spinal cord by radicular filaments, fila radicularia.

The posterior root in the area of ​​the posterolateral sulcus is connected to the spinal cord by the radicular filaments of the dorsal root, fila radicularia radicis dorsalis, and the anterior root in the area of ​​the anterolateral sulcus is connected to the radicular filaments of the anterior root, fila radicularia radicis ventralis.

The posterior roots are thicker, since each of them belongs to a spinal node [sensitive], ganglion spinale.

The exception is the first cervical nerve, whose anterior root is larger than the posterior one. Sometimes there is no node in the root of the coccygeal nerve.

The anterior roots do not have nodes. At the site of formation of the spinal nerves, the anterior roots are only adjacent to the spinal ganglia and are connected to them using connective tissue.

The connection of the roots into the spinal nerve occurs lateral to the spinal ganglion.

The roots of the spinal nerves first pass through the subarachnoid space and are surrounded directly by the pia mater.

The dentate ligament runs between the anterior and posterior roots in the subarachnoid space. Near the intervertebral foramina, the roots are densely covered with all three meninges, which grow together and continue into the connective tissue sheath of the spinal nerve (see Fig. 879, 954, 956).

The roots of the spinal nerves are directed from the spinal cord to the intervertebral foramen (see Fig. 879, 997):

1) the roots of the upper cervical nerves are located almost horizontally;

2) the roots of the lower cervical nerves and two upper thoracic nerves go obliquely downward from the spinal cord, located before entering the intervertebral foramen one vertebra below the point of origin from the spinal cord;

3) the roots of the next 10 thoracic nerves follow even more obliquely downwards and, before entering the intervertebral foramen, are approximately two vertebrae below their origin;

4) the roots of the 5th lumbar, 5th sacral and coccygeal nerves are directed downwards vertically and form, with the roots of the same name on the opposite side, a horse’s tail, cauda equina, which is located in the cavity of the dura mater.

Separating from the cauda equina, the roots are directed outward and, while still in the spinal canal, are connected into the trunk of the spinal nerve, truncus n.

Most spinal nodes lie in the intervertebral foramina; the lower lumbar nodes are located partially in the spinal canal; The sacral nodes, except the last one, lie in the spinal canal outside the dura mater. The spinal ganglion of the coccygeal nerve is located inside the cavity of the dura mater.

Spinal nerve roots and spinal nodes can be examined after opening the spinal canal and removing the vertebral arches and articular processes.

All trunks of the spinal nerves, with the exception of the first cervical, fifth sacral and coccygeal nerves, lie in the intervertebral foramina, while the lower ones, which take part in the formation of the cauda equina, are also partially located in the spinal canal.

The first cervical spinal nerve (CI) passes between the occipital bone and the first cervical vertebra; the eighth cervical spinal nerve (CVIII) is located between the VII cervical vertebra and the I thoracic vertebra; the fifth sacral and coccygeal nerves exit through the sacral fissure.

Rice.

1060. The course of the fibers of the spinal nerves and their connection with the sympathetic trunk (diagram).

The spinal nerve trunks are mixed, that is, they carry sensory and motor fibers. Each nerve, upon exiting the spinal canal, almost immediately divides into an anterior branch, r. ventralis, and posterior branch, r. dorsalis, each of which contains both motor and sensory fibers (see.

rice. 880, 955, 995, 1060). Spinal nerve trunk through connecting branches, rr. communicantes, is associated with the corresponding node of the sympathetic trunk.

There are two connecting branches. One of them carries prenodal (myelin) fibers from the cells of the lateral horns of the spinal cord. It is white [these branches are from the eighth cervical (CVIII) to the second-third lumbar (LII-LIII) spinal nerve] and is called the white communicating branch, r.

communicans albus. Another connecting branch carries postnodal (mostly unmyelinated) fibers from the nodes of the sympathetic trunk to the spinal nerve.

It is darker in color and is called the gray connecting branch, r. communicans griseus.

A branch departs from the trunk of the spinal nerve to the dura mater of the spinal cord - the meningeal branch, r. meningeus, which also contains sympathetic fibers.

The meningeal branch returns to the spinal canal through the intervertebral foramen. Here the nerve is divided into two branches: a larger one, running along the anterior wall of the canal in an ascending direction, and a smaller one, running in a descending direction.

Each of the branches connects both with the branches of neighboring branches of the meninges, and with the branches of the opposite side. As a result, a plexus of the meninges is formed, which sends a branch to the periosteum, bones, membranes of the spinal cord, venous vertebral plexuses, as well as to the arteries of the spinal cord.

In the neck area, spinal nerves take part in the formation of the vertebral plexus, plexus vertebralis, around the vertebral artery.

Posterior branches of the spinal nerves

Rice. 1029. Areas of distribution of cutaneous nerves of the body; rear view (semi-schematic). Rice.

Spinal nerves. Spinal nerves (nn

Intercostal nerves, arteries and veins; view from above and slightly from the front. (The skin of the anterolateral parts of the chest within the V-VI ribs was removed; the parietal layer of the pleura and the intrathoracic fascia were removed.)

Posterior branches of the spinal nerves, rr. dorsales nn. spinalium(see Fig. 995, 1027, 1029), with the exception of the two upper cervical nerves, are much thinner than the anterior ones. All posterior branches from their origin, at the lateral surface of the articular processes of the vertebrae, are directed back between the transverse processes of the vertebrae, and in the region of the sacrum they pass through the dorsal sacral foramina.

Rice.

1028. Nerves of the trunk. (Back surface). (Posterior branches of the spinal nerves: on the left - cutaneous branches, on the right - muscular.)

Each posterior branch divides into a medial branch, r. medialis, and on the lateral branch, r. lateralis. Both branches contain sensory and motor fibers.

The terminal branches of the posterior branches are distributed in the skin of all dorsal regions of the body, from the occipital to the sacral region, in the long and short muscles of the back and in the muscles of the back of the head (see Fig. 995, 1027, 1028).

Anterior branches of the spinal nerves

Anterior branches of the spinal nerves, rr.

ventrales nn. spinalium, thicker than the posterior ones, with the exception of the first two cervical nerves, where there are inverse relationships.

The anterior branches, except for the thoracic nerves, near the spinal column are widely interconnected and form plexuses, plexus.

Of the anterior branches of the thoracic nerves, branches from ThI and ThII, sometimes ThIII (brachial plexus), and from ThXII (lumbar plexus) take part in the plexuses. However, these branches only partially enter the plexus.

Rice.

998. Cervical plexus, plexus cervicalis (semi-schematic).

Topographically, the following plexuses are distinguished: cervical; shoulder; lumbosacral, in which the lumbar and sacral are distinguished; coccygeal (see

All these plexuses are formed by connecting the corresponding branches in the form of loops.

The cervical and brachial plexuses are formed in the neck, the lumbar - in the lumbar region, the sacral and coccygeal - in the pelvic cavity.

Branches depart from the plexuses, which go to the periphery of the body and, branching out, innervate its corresponding sections. The anterior branches of the thoracic nerves, which do not form plexuses, continue directly to the periphery of the body, branching in the lateral and anterior sections of the walls of the chest and abdomen.

Lumbar, sacral and coccygeal nerves

Lumbar, sacral and coccygeal nerves, nn.

lumbales, sacrales et coccygeus, like all overlying spinal nerves, give off 4 groups of branches: meningeal, connective, anterior and posterior.

The anterior branches of the lumbar, sacral and coccygeal spinal nerves (LI–LV, SI–SV, CoI–CoII) form one common lumbosacral plexus, plexus lumbosacralis.

In this plexus, the lumbar plexus (ThXII, LI–LIV) and the sacral plexus (LIV–LV–CoI) are topographically distinguished.

The sacral plexus is divided into the sacral plexus itself and the coccygeal plexus (SIV–CoI, CoII) (see Fig. 997).

Search Lectures

Lecture No. 13

Plan:

Mixed cranial nerves.

Spinal nerves: formation, number, branches of the spinal nerves.

Plexus of spinal nerves.

General concept of the peripheral nervous system.

Peripheral nervous system- This is the part of the nervous system located outside the brain and spinal cord.

Provides two-way communication between the central parts of the nervous system and the organs and systems of the body.

The peripheral nervous system includes:

- cranial nerves

- spinal nerves

- sensory ganglia of cranial and spinal nerves

- ganglia and nerves of the autonomic nervous system.

There are 12 pairs of cranial nerves, and 31 pairs of spinal nerves.

Cranial nerves: sensory and motor cranial nerves.

Humans have 12 pairs of cranial nerves that arise from the brain stem.

Each nerve has its own name and serial number, indicated by a Roman numeral.

I para-olfactory nerve (n.olfactorius)

II pair - optic nerve (n.

III point - oculomotor (n. oculomotorius)

IV p. -trochlear nerve (n. trochlearis)

V pair - trigeminal nerve (n. trigeminus)

VI p. - abducens nerve (n. abducens)

VII point - facial nerve (n. facialis)

VIII paragraph - vestibular-cochlear nerve (n. vestibulocochlearis)

IX point - glossopharyngeus nerve (n. glossopharyngeus).

X n, - vagus nerve (n. vagus)

XI point - accessory nerve (n.

XII hypoglossal nerve (n. hypoglyssus)

They perform various functions and are divided into sensory, motor and mixed.

Sensory and motor cranial nerves

TO sensory nerves include:

— 1 pair - olfactory nerve.

- II pair - visual and

- VIII p. - vestibulocochlear nerve.

Olfactory nerve consists of the central processes of olfactory cells, which are located in the mucous membrane of the nasal cavity.

The olfactory nerves, numbering 15-20 filaments (nerves), pass into the cranial cavity through the perforated plate. In the cranial cavity, the fibers of the olfactory nerves enter the olfactory bulbs, which continue into the olfactory tracts. Then they go to the subcortical centers of smell and the cortex of the temporal lobe of the brain.

Function: smell perception.

Optic nerve formed by processes of ganglion cells of the retina. Having entered the cranial cavity through the optic canal, the right and left optic nerves partially intersect and continue into the visual tracts, which go to the subcortical centers of vision and to the occipital lobe of the cerebral hemispheres.

Function: form the organ of vision.

vestibulocochlear nerve formed by the central processes of neurons that lie in the inner ear (organ of Corti and ottolith).

Anatomy and structure of spinal nerves in the human body, functions and dysfunctions

Penetrates into the cranial cavity through the internal auditory opening. The cochlear part goes to the subcortical hearing centers, and the vestibular part goes to the nuclei of the olive and cerebellum, then both nerves go to the temporal lobe of the cerebral hemispheres.

Functions - the vestibular part is involved in regulating the position of the body in space and coordinating movements.

The cochlea forms hearing.

Motor cranial nerves include:

• IV point - trochlear nerve,
• VI p. - abducens nerve,
• X1 p.

- accessory nerve

• XII point - hypoglossal nerve.

Trochlear nerve starts from the motor nucleus, which is located in the midbrain. This nerve goes into the orbit where it innervates the superior oblique muscle of the eye.

Abducens nerve starts from the motor nuclei located in the hindbrain pons. It goes into the orbit, where it innervates the lateral (abductor) muscle of the eye.

Accessory nerve starts from the motor nuclei located in the medulla oblongata.

Innervates the sternocleidomastoid and trapezius muscles.

Hypoglossal nerve starts from the motor nuclei located in the medulla oblongata. Innervates the muscles of the tongue and some muscles of the neck.

Mixed CMN.

Mixed nerves include:

• III point - oculomotor nerve,
• V p. - trigeminal nerve,
• VII point - facial nerve,
• IX point - glossopharyngeal nerve,

- vagus nerve

Oculomotor nerve contains motor and

parasympathetic fibers. The nuclei are located in the midbrain. It goes into the cavity of the orbit, where it innervates the muscles of the eyeball (superior, inferior, medial rectus and inferior oblique muscles) with motor fibers, and innervates the muscle that constricts the pupil and the ciliary muscle with parasympathetic fibers.

Trinity nerve has sensory and motor fibers.

It forms three large branches:

1. The ophthalmic nerve (p. oftalmiciis) is sensitive/goes to the orbit, where it is divided into branches innervating the skin of the forehead, sinuses, except the maxillary, eyeball, upper eyelid.

2. Maxillary nerve (n.

maxillaris) sensitive, divided into branches innervating the maxillary sinus and ethmoid cells, nasal cavity, palate, and teeth of the upper jaw.

3. The mandibular nerve (n. mandibularis) is mixed, has motor and sensory fibers. Sensory fibers innervate the skin of the auricle, cheek, lower teeth and tongue, and motor fibers innervate the masticatory muscles.

Facial nerve contains motor, sensory and autonomic (parasympathetic) fibers.

The nuclei are located in the hindbrain. Motor fibers innervate the facial muscles and subcutaneous muscle of the neck, sensory fibers provide taste

sensitivity of the anterior 2/3 of the tongue, and parasympathetic fibers innervate the submandibular and sublingual salivary glands.

Glossopharyngeal nerve contains motor, sensory and autonomic parasympathetic fibers.

The nuclei are located in the medulla oblongata. Motor fibers innervate the muscles of the pharynx, sensory fibers provide taste sensitivity to the posterior third of the tongue, and parasympathetic fibers innervate the parotid salivary gland.

Vagus nerve has motor, sensory and parasympathetic fibers. It innervates all internal organs of the chest and abdominal cavity up to the sigmoid colon. On the neck it gives off branches to the pharynx, esophagus, and larynx.

Spinal nerves: formation, number, branches of the spinal nerves.

There are 31 pairs of SMNs in total.

There are 5 groups of spinal nerves:

• 8 neck,
• 12 breasts,
• 5 lumbar,
• 5 sacral and
• 1 coccygeal nerve.

Their number corresponds to the number of spinal cord segments. Each spinal nerve is formed by the fusion of the anterior and posterior roots of the spinal cord. The spinal nerves have mixed functions. Each spinal nerve, passing through the intervertebral foramina in a single short trunk, is divided into branches:

front

3. meningeal

4. connecting

Connecting branch goes to the nodes of the sympathetic trunk.

Meningeal branch goes back into the spinal canal and innervates the membranes of the spinal cord.

Posterior branches go steeply back and innervate the skin and muscles of the back of the head, back, lower back in the spinal column, and partially the skin of the gluteal region. The posterior branches retain a segmental structure.

Anterior branches spinal nerves are thicker and longer than the posterior ones.

Unlike the posterior branches, the segmental structure preserves only the anterior branches of the thoracic nerves, while all the others (cervical, lumbar, sacral and coccygeal) form plexuses.

The anterior branches of the thoracic nerves do not form plexuses; they innervate the skin and muscles of the chest and abdomen.

And they are called intercostal nerves, and the 12th thoracic nerve is called the subcostal nerve.

Media plexus.

There are:

1) cervical plexus

2) brachial plexus

3) lumbar plexus

4) sacral plexus

Cervical plexus formed by the anterior branches of the 4 upper cervical spinal nerves.

It is located behind the sternocleidomastoid muscle. The nerves that innervate the skin of the neck, the lateral parts of the occipital region, and the muscles of the neck depart from the cervical plexus. The largest nerve of this plexus is the phrenic nerve, which innervates the diaphragm with motor branches and the pleura and pericardium with sensory branches.

Brachial plexus formed by the anterior branches of the 4 lower cervical and partially the 1st thoracic nerve.

It is located between the scalene muscles and descends behind the collarbone into the armpit. From the brachial plexus arise the nerves that innervate the muscles and skin of the neck, shoulder girdle (pectoralis major and minor, infraspinatus and supraspinatus, rhomboids, serratus anterior, latissimus dorsi) and upper limb.

The major branches of the brachial plexus are:

1) musculocutaneous nerve- innervates the anterior shoulder muscles and the skin of the anterolateral surface of the forearm.

2) Median nerve - does not give branches on the shoulder, goes to the forearm and innervates the muscles of the anterior group of the forearm, then the palmar side of the hand and the skin of the 3.5 fingers (starting with the thumb).

3) Ulnar nerve - does not give branches on the shoulder, on the forearm it innervates all the remaining muscles of the anterior group, goes to the hand and innervates all the remaining muscles of the palm and the skin of 1.5 on the palmar side, 2.5 fingers on the back side, starting with the little finger.

4) Radial nerve-innervates the muscles and skin of the posterior surface of the shoulder, forearm, then goes to the back of the hand and innervates the skin of 2.5 fingers, starting with the thumb.

Lumbar plexus - formed by the anterior branches of the 3 upper lumbar nerves and partly the 12 thoracic and 4 lumbar nerves.

It is located in the thickness of the psoas major muscle.

Lumbar plexus nerves:

1) Femoral nerve- the largest nerve of this plexus. Innervates the muscles of the anterior thigh, the skin of the anteromedial side of the leg and foot.

2) Obturator nerve- innervate the muscles of the medial group of the thigh (adductor muscles) and the skin above them.

3) Lateral cutaneous nerve of the thigh- innervates the skin of the thigh on the lateral side.

The short nerves of this plexus innervate the muscles and skin of the lower abdomen, groin and genitals.

Sacral plexus- formed by the anterior branches of all the sacral and coccygeal nerves, partially the 5th lumbar nerve.

It is located on the anterior surface of the sacrum (on the piriformis muscle).

Short branches of this plexus innervate the pelvic muscles and the skin and muscles of the perineum.

Long branches:

1) Posterior cutaneous nerve of the thigh - innervates the skin of the back of the thigh and gluteal region.

2) The sciatic nerve is the largest nerve in the human body, runs along the back of the thigh and innervates the posterior group of thigh muscles. Further, in the popliteal fossa, the sciatic nerve divides into two branches: the tibial and common peroneal nerves.

Tibial nerve- innervates the muscles and skin of the posterior surface of the leg, in the foot area it is divided into medial and lateral plantar nerves.

They innervate the muscles and skin of the sole.

Common peroneal nerve innervates the muscles of the lateral and anterior groups of the lower leg and the skin of the dorsum of the foot.

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