Lumbosacral plexus. Sacral plexus, plexus sacralis. Short branches of the sacral plexus Where is the sacral plexus of spinal nerves located?

The sacral (sacrococcygeal) plexus (see Fig. 76) is formed by the anterior branches of the fifth lumbar (L 5), all sacral (S 1–S 5) and coccygeal nerves (Co 1), as well as part of the fibers of the fourth lumbar spinal nerve ( L 4). The sacral plexus is located on the anterior surface of the sacrum.

Short and long branches emerge from the sacral plexus. Short branches end in the pelvic girdle; they innervate the muscles and organs of the pelvic cavity and perineum. Long branches innervate the bones, muscles, joints and skin of the free lower limb.

The short branches of the sacral plexus include branches to the pelvic muscles(piriformis, gemellus, obturator internus), quadratus femoris, gluteal nerves(upper and lower) to the gluteal muscles, pudendal nerve, going to the skin and muscles of the perineum, to the external genitalia.

The long branches of the sacral plexus include posterior cutaneous nerve of the thigh and sciatic nerve.

Posterior cutaneous nerve The femur exits the pelvic cavity along with the sciatic, inferior gluteal and pudendal nerves through the infrapiriform foramen and innervates the skin of the posterior thigh and gluteal region.

Sciatic nerve, the largest nerve in the human body, exits to the back of the thigh, where it gives branches to the leg muscles (biceps femoris, semitendinosus and semimembranosus muscles). In the popliteal fossa, the sciatic nerve divides into the large tibial and common peroneal nerves.

tibial nerve, having given medial cutaneous nerve of the calf(to the skin of the medial surface of the leg), goes down between the superficial and deep muscles of the leg (in the ankle-popliteal canal) and innervates all posterior muscles shins. The tibial nerve then curves around the medial malleolus from behind and goes to the sole of the foot, where it divides to the medial And lateral plantar nerves, innervating the muscles and skin of the foot.

Common peroneal nerve from the popliteal fossa comes laterally, gives off lateral cutaneous nerve of the calf(to the skin of the posterolateral surface of the leg) and at the level of the head fibula divided into superficial and deep peroneal nerves.

Superficial peroneal nerve innervates the long and short peroneus muscles and the skin of the dorsum of the foot (except for the skin in the area of ​​the big toe and the first interdigital space). Deep peroneal nerve passes along with the anterior tibial artery between the muscles of the anterior group of the leg, innervates these muscles. In the foot, the deep peroneal nerve innervates the short extensor muscles of the fingers and the skin in the area of ​​the first interdigital space.

Medial And lateral calf nerves(branches of the tibial and common peroneal nerves) connect on the back surface of the leg, form saphenous nerve, innervating the skin of the lateral edge of the foot.

11. Autonomic (autonomic) nervous system: general issues

Vegetative (plant), or autonomous(Greek autos-myself, nomos- law; that is, acting according to its own laws, not subject to consciousness), system from the entire nervous system is isolated due to the peculiarities of its structure and functions (see section 3).

The structure of the autonomic nervous system differs from the somatic one:

local location of brain autonomic centers in three parts of the central nervous system: in the brain stem (autonomic nuclei of the cranial nerves), in the thoracic and sacral segments of the spinal cord (lateral columns of gray matter) (Fig. 77);

lack of segmentation (metamericity) in the innervation of organs.

the presence of autonomic ganglia* outside the central nervous system, forming autonomic nerve plexuses and sympathetic trunks;

two-neuronality of the efferent pathway (Fig. 78): the first efferent neuron is located in the central nervous system, the second neuron is in the autonomic ganglion**;

the nerve fibers of the autonomic nervous system are thin, unmyelinated (type C) or weakly myelinated (type B), which causes slow transmission of nerve impulses compared to the somatic system;

Autonomic nervous system responsible for maintaining the body’s most important life support functions. It innervates all internal organs (respiratory, digestive and excretory systems), endocrine glands, which determine the intensity metabolic processes in the body, the cardiovascular system (including the vessels of striated muscles) and the genitals.

Autonomic functions are regulated reflexively, without the participation of consciousness. The simplest reflex arc The autonomic reflex, like the somatic reflex arc, consists of three links: sensitive (afferent), intercalary (conductor, switching) and motor or secretory (effector) (see Fig. 78).

Autonomic afferents conduct impulses from chemo- and mechanoreceptors located in the walls and on the inner surface of the mucous membranes of the gastrointestinal tract, bronchial tree, genitourinary system, on the inner surface of blood vessels (in the aortic arch and at the place of division of the common carotid artery into the internal and external carotid arteries). These receptors perceive the parameters of the functioning of internal organs (the degree of stretching of the walls of hollow organs - the stomach, intestines, gall bladder, bladder, etc.) and indicators of homeostasis (the chemical composition of the contents of the stomach and intestines, the content of oxygen, carbon dioxide, pH in the blood, etc.). d.).

Since most autonomic sensory neurons are located in the walls of internal organs, they are classified as metasympathetic nervous system. However, some of them transmit impulses to overlying centers, and therefore at the same time can be an afferent link of sympathetic or parasympathetic reflex arcs (Fig. 79).

Impulses can be transmitted from autonomic sensory neurons (see Fig. 79):

intercalary or motor neurons of the metasympathetic (intramural) system,

efferent neurons of the sympathetic system located in the autonomic ganglia,

neurons of the autonomic centers located in the central nervous system (sympathetic centers are located in the lateral horns of the thoracolumbar segments C 8 -L 2 (sometimes in the L 3 segment), parasympathetic - in the autonomic nuclei of the III, VII, IX and X pairs of cranial nerves, as well as in the lateral horns of the sacral segments S 2 – S 4)

neurons of the reticular formation and hypothalamus.

Interneurons of the autonomic reflex arc can be located at different levels: in the walls of organs (in the metasympathetic system), in the autonomic ganglia, as well as in the sympathetic or parasympathetic centers located in the spinal cord and brain (see Fig. 79). The higher their location, the larger and more varied the volume of information they process and the wider their area of ​​influence.

The main differences between the metasympathetic, sympathetic and parasympathetic systems lie in the level of localization of their central and efferent neurons, as well as in the number of neurons that make up the efferent pathway.

Related information.

1. Internal obturator nerve, n. obturatorius internus, arises from the lumbosacral trunk and the anterior branch of the first sacral nerve (SI). Coming out of the pelvis under piriformis muscle th, the nerve goes around the ischial spine, approaches the obturator internus muscle, sometimes giving a small branch to the superior gemellus muscle.

2. Nerve of the piriformis muscle, n. piriformis, formed by two trunks extending from the posterior surface of the anterior branches of the first and second sacral nerves (SI, SII); With a common trunk, the nerve approaches the piriformis muscle and innervates it.

3. Nerve of the quadratus femoris muscle, n. quadratus femoris, originates from the anterior surface of the lumbosacral trunk and the first sacral nerve. Coming out of the pelvis under the piriformis muscle, it gives off terminal branches to the quadratus femoris muscle. Descending slightly in front of the sciatic nerve, it sends branches to the twin muscles and the capsule of the hip joint.

4. Superior gluteal nerve, n. gluteus superior(LIV, LV, SI), leaves the pelvic cavity, accompanied by the vessels of the same name, through the gap above the piriformis muscle and, bending around the greater sciatic notch, lies between the gluteus medius and minimus muscles, moving in an arched manner forward. Having given branches to the indicated muscles, the nerve is distributed with its terminal branches in the thickness of the tensor fascia lata.

5. Inferior gluteal nerve, n. gluteus inferior(LV, SI, SII), leaves the pelvic cavity through the gap under the piriformis muscle into the gluteal region under the gluteus maximus muscle along with the pudendal nerve (lateral to it), the sciatic nerve and the posterior cutaneous nerve of the thigh (medial to them). It branches in the thickness of the gluteus maximus muscle, also innervating the capsule of the hip joint. Sometimes the nerve takes part in the innervation of the obturator internus, gemellus and quadratus femoris muscles.

6. Posterior cutaneous nerve of the thigh, n. cutaneus femoris posterior, initially adjacent to the inferior gluteal nerve or along a common trunk with it; exits the pelvic cavity through a gap under the piriformis muscle medial to the sciatic nerve and lies under the gluteus maximus muscle, located almost in the middle between the ischial tuberosity and the greater trochanter of the femur, and descends to the posterior surface of the thigh. Here it is located immediately under the fascia lata, corresponding to the groove between the semitendinosus and biceps femoris muscles; heading down, it gives off branches that extend on both sides of the main trunk and pierce the fascia along the back of the thigh. The branches branch in the skin of the posterior and especially medial surfaces of the thigh, reaching the skin of the popliteal fossa.

Branches of the posterior cutaneous nerve of the thigh:

1) lower nerves of the buttocks, nn. clunium inferiores, moving away from the main trunk with 2-3 branches, bend around or pierce the lower edge of the gluteus maximus muscle, go upward and branch in the skin of the gluteal region;

2) perineal branches, rr. perineales, only 1-2, sometimes more - thin nerves, depart from the main trunk, go down and, bending around the ischial tuberosity, follow anteriorly, branching in the skin of the medial surface of the scrotum (labia majora) and perineum. These branches connect with the branches of the pudendal nerve of the same name.

7. Sciatic nerve, n. ischiadicus(LIV, LV, SI - SIII) - the thickest nerve not only of the lumbosacral plexus, but of the entire body; is a direct continuation of all the roots of the sacral plexus. Upon exiting through the gap under the piriformis muscle, the sciatic nerve is located lateral to all the nerves and vessels passing through this opening, and lies between the gluteus maximus muscle on one side and the gemelli, internal obturator muscles and quadratus femoris muscle on the other, almost in the middle of the line drawn between the ischial tuberosity and the greater trochanter of the femur. Even before exiting through the gap, an articular branch departs from the sciatic nerve to the capsule of the hip joint.

Coming from under the lower edge of the gluteus maximus muscle, the sciatic nerve is located in the region of the gluteal fold close to the fascia lata of the thigh; further down it is covered by the long head of the biceps femoris muscle, located between it and the adductor magnus muscle. In the middle of the thigh, a long head crosses it; below it is located between the semimembranosus muscle medially and the biceps femoris muscle laterally and reaches the popliteal fossa, where in its upper corner it is divided into two branches: a thicker medial one - the tibial nerve and a thinner lateral one - the common peroneal nerve.

The division of the sciatic nerve into these two branches can sometimes occur above the popliteal fossa, even directly at the sacral plexus itself. In this case, from the pelvic cavity, the tibial nerve passes under the piriformis muscle, and the common peroneal nerve can pierce this muscle or pass over it. Both of these branches, throughout the entire sciatic nerve, lie in a common connective tissue sheath, after opening which, it is easy to separate them to the sacral plexus. Along the line of contact of the tibial and common peroneal nerves passes the artery accompanying the sciatic nerve.

Branches of the sciatic nerve:

1) muscle branches, rr. musculares, branch in the following muscles: m. obturatorius interims, mm. gemelli superior et inferior, m. quadratus femoris.

The muscular branches arise either before or within the passage of the sciatic nerve through the foramen under the piriformis muscle. In addition, muscle branches in the thigh area extend from the tibial part of the sciatic nerve to m. biceps femoris (caput longum), m. semitendinosus, m. semimembranosus, m. adductor magnus. From the peroneal part of the sciatic nerve, the muscle branches go to m. biceps femoris (caput breve);

2) articular branches depart from the tibial and peroneal parts of the sciatic nerve to the articular capsule of the knee joint;

3) common peroneal nerve, n. fibularis communis(LIV, Lv, SI, SII), from the proximal apex of the popliteal fossa goes to its lateral side and is located under the medial edge of the biceps femoris muscle, between it and the lateral head of the gastrocnemius muscle, spirals around the head of the fibula, being covered here only by fascia and skin .

In this area, non-permanent articular branches extend from the nerve trunk to the lateral parts of the knee joint capsule, as well as to the tibiofibular joint. Distal to this area, it penetrates into the thickness of the initial part of the peroneus longus muscle, where it divides into its two terminal branches - the superficial peroneal nerve and the deep peroneal nerve.

Branches arise from the common peroneal nerve:

a) lateral cutaneous nerve of the calf, n. cutaneus surae lateralis, departs in the popliteal fossa, goes to the lateral head of the gastrocnemius muscle and, piercing the fascia of the leg in this place, branches in the skin of the lateral surface of the leg, reaching the area of ​​the lateral malleolus;

b) fibular connecting branch, r. communicans fibularis, can start from the main trunk or from the lateral cutaneous nerve of the leg, follows the lateral head of the gastrocnemius muscle, located between it and the fascia of the leg, pierces the latter and, branching in the skin, connects with the medial cutaneous nerve of the leg;

c) superficial peroneal nerve, n. fibularis superficialis, passes between the heads of the long peroneal muscle, follows down, located at some distance between both peroneal muscles. Having passed to the medial surface of the peroneus brevis muscle, the nerve pierces the fascia of the leg in the region of the lower third of the leg and branches into its terminal branches: the dorsal medial and intermediate cutaneous nerves (foot).

Branches of the superficial peroneal nerve:

muscle branches, rr. musculares, innervate the peroneus longus muscle (2-4 branches from the proximal parts of the trunk) and the peroneus brevis muscle (1-2 branches from the trunk in the middle third of the leg);

medial dorsal cutaneous nerve, m. cutaneus dorsalis medialis,- one of the two terminal branches of the superficial peroneal nerve. It follows for some distance over the fascia of the leg, goes to the medial edge of the dorsum of the foot, gives off branches to the skin of the medial ankle, where it connects with the branches of the saphenous nerve of the leg, after which it divides into two branches. One of them, the medial one, branches in the skin of the medial edge of the foot and big toe to the distal phalanx and connects in the area of ​​the first interosseous space with the deep peroneal nerve. The other branch, the lateral one, connects with the terminal branch of the deep peroneal nerve and goes to the area of ​​the second interosseous space, where it branches in the surfaces of the II and III fingers facing each other, giving here the dorsal digital nerves of the foot, nn. digitales dorsales pedis;

d) intermediate dorsal cutaneous nerve, n. cutaneus dorsalis intermedius, like the medial dorsal cutaneous nerve, is located over the fascia of the leg and follows the anterolateral surface of the dorsum of the foot. Having given off branches to the skin of the area of ​​the lateral ankle, which connect with the branches of the sural nerve, it is divided into two branches, of which one, going medially, branches in the skin of the surfaces of the third and fourth fingers facing each other. The other, lying more lateral, is directed to the skin of the surfaces of the fourth finger and little finger facing each other and to the lateral surface of the little finger, here forming a connection with the terminal branch of the sural nerve. All these branches are called the dorsal digital nerves of the foot, nn. digitales dorsales pedis;

e) deep peroneal nerve, n. fibularis (peroneus) profundus, perforating the thickness of the initial sections of the long peroneus muscle, the anterior intermuscular septum shins and extensor longus fingers, lies on the anterior surface of the interosseous membrane, located on the lateral side of the anterior tibial vessels.

Next, the nerve passes to the anterior and then to the medial surface of the vascular bundle, is located in the upper parts of the leg between the long extensor of the digitorum and the anterior tibialis muscle, and in the lower parts - between the anterior tibial muscle and the long extensor of the big toe, innervating them. The deep peroneal nerve has intermittent connecting branches with the superficial peroneal nerve.

When passing to the dorsum of the foot, the nerve first passes under the superior extensor retinaculum, giving off a non-permanent articular branch to the capsule ankle joint, and then under the inferior extensor retinaculum and the tendon of the long extensor of the big toe and is divided into two branches: lateral and medial.

The first is shorter, most of its branches are directed to the short extensor fingers. The second branch is longer, accompanied by the dorsal artery of the foot, reaches the area of ​​the first interosseous space, where, passing under the tendon of the short extensor of the big toe together with the first dorsal metatarsal artery, it is divided into two terminal branches, branching in the skin of the dorsum of the sides I and facing each other. II fingers. Along with them, a variable number of thin branches depart, approaching the capsules of the metatarsophalangeal and interphalangeal joints of the first and second fingers from their dorsal surface.

Branches of the deep peroneal nerve:

a) muscle branches, rr. musculares, in the lower leg area are directed to the following muscles: m. tibialis anterior - 3 branches that enter the upper, middle and lower parts of the muscle, to m. extensor digitorum longus and m. extensor hallucis longus - 2 branches each that enter the upper, middle and lower parts of the muscles. In the area of ​​the dorsum of the foot, the muscle branches approach m. extensor digitorum brevis and m. extensor hallucis brevis;

b) dorsal digital nerves, nn. digitales dorsales, - terminal branches of the deep peroneal nerve. They are divided into two nerves: the lateral nerve of the big toe (branches in the skin of the dorsum of the first toe from its lateral edge) and the medial nerve of the second toe (innervates the skin of the dorsum of the toe from its medial edge);

4) tibial nerve, n. tibialis(LIV, Lv, SI, SII, SIII), being in its direction a continuation of the sciatic nerve, much thicker than its second branch - the common peroneal nerve. It begins at the top of the popliteal fossa, follows almost vertically to its distal angle, located in the area of ​​the fossa directly under the fascia, between it and the popliteal vessels.

Further, following between both heads of the gastrocnemius muscle, it lies on the posterior surface of the popliteus muscle and, accompanied by the posterior tibial vessels, passes under the tendinous arch of the soleus muscle, being here covered by this muscle.

Heading further down under the deep layer of fascia of the leg between the lateral edge of the flexor digitorum longus and the medial edge of the flexor hallucis longus, the tibial nerve reaches the posterior surface of the medial malleolus, where it is located midway between it and the calcaneal tendon. After passing under the flexor retinaculum, the nerve divides into its two terminal branches: the medial plantar nerve and the lateral plantar nerve.

Branches of the tibial nerve:

a) muscle branches, rr. musculares, are directed to the following muscles: to the heads of the gastrocnemius muscle (the branch of the medial head is thicker than the lateral one); to the soleus muscle (anterior and posterior branches); to the popliteus muscle, to the plantaris muscle. The branches approaching the popliteus muscle send branches to the capsule of the knee joint and the periosteum of the tibia;

b) interosseous nerve of the leg, n. interosseus cruris,- enough long nerve. flexor of the fingers;

c) medial cutaneous nerve of the calf, n. cutaneus surae medialis, departs in the area of ​​the popliteal fossa from the posterior surface of the tibial nerve, follows under the fascia, accompanied by the small saphenous vein running medially between the heads of the gastrocnemius muscle. Having reached the middle of the lower leg, approximately at the level of the beginning of the calcaneal tendon, sometimes higher, it pierces the fascia, after which it connects with the peroneal connecting branch, r. communicans peroneus (fubularis), into one trunk - sural nerve, n. suralis.

The latter runs along the lateral edge of the calcaneal tendon, accompanied by the small saphenous vein located medially from it and reaches the posterior edge of the lateral malleolus, where it sends the lateral calcaneal branches, rr, into the skin of this area. calcanei laterales, as well as branches to the ankle joint capsule.

Next, the sural nerve goes around the ankle and passes to the lateral surface of the foot in the form of the lateral dorsal cutaneous nerve, n. cutaneus dorsalis lateraslis, which branches in the skin of the dorsum and lateral edge of the foot and the dorsum of the fifth toe and gives off a connecting branch to the intermediate dorsal cutaneous nerve of the foot;

d) medial calcaneal branches, rr. calcanei mediates, penetrate the fascia in the area of ​​the ankle groove, sometimes in the form of a single nerve, and branch in the skin of the heel and medial edge of the sole;

e) medial plantar nerve, n. plantaris medialis, - one of the two terminal branches of the tibial nerve. The initial sections of the nerve are located medial to the posterior tibial artery, in the canal between the superficial and deep layers of the flexor retinaculum. After passing through the canal, the nerve is directed, accompanied by the medial plantar artery, under the abductor muscle of the big toe. Following further forward between this muscle and the flexor digitorum brevis, it is divided into two parts - medial and lateral.

The medial plantar nerve gives off several cutaneous branches to the skin of the medial surface of the plantar:

muscle branches to m. abductor hallucis, m. flexor digitorum brevis, m. flexor hallucis brevis and common plantar digital nerves I, II, III, nn. digitales plantares communes I, II, III. The latter are accompanied by the metatarsal plantar arteries, send muscle branches to the first and second (sometimes to the third) vermiform muscles and pierce the plantar aponeurosis at the level of the distal end of the interosseous spaces. Having given thin branches here to the skin of the sole, they are divided into their own plantar digital nerves, nn. digitales plantares proprii, branching in the skin of the sides of the plantar surface of the I and II, II and III, III and IV fingers facing one another, and pass to the dorsal surface of their distal phalanges;

e) lateral plantar nerve, n. plantaris lateralis, is the second terminal branch of the tibial nerve, much thinner than the medial plantar nerve. Passing on the sole, accompanied by the lateral plantar artery, between the quadratus plantaris muscle and the flexor digitorum brevis muscle, it lies closer to the lateral edge of the foot between the flexor digiti brevis muscle and the abductor digiti minimi muscle, where it divides into its terminal branches: superficial and deep.

Branches of the lateral plantar nerve:

muscle branches extend from the main trunk before dividing it into terminal branches and are directed to the quadratus plantae muscle and to the abductor little finger muscle;

superficial branch, r. superficialis Having given several branches to the skin of the sole, it is divided into medial and lateral branches. Medial branch- common plantar digital nerve, n. digitalis plantaris communis (IV and V fingers), which, accompanied by the metatarsal plantar artery, passes through the fourth interosseous space. Approaching the metatarsophalangeal joint and sending a connecting branch to the medial plantar nerve, it divides into two proper plantar digital nerves, nn. digitales plantares propria. The latter branch in the skin of the sides of the IV and V fingers facing one another and pass to the dorsal surface of their nail phalanges. Lateral branch- the own plantar nerve of the fifth finger, which branches in the skin of the plantar surface and the lateral side of the fifth finger. This nerve often gives off muscular branches to the interosseous muscles of the fourth intermetatarsal space and to the flexor of the little finger;

deep branch, r. profundus, accompanied by the plantar arch artery, is located between the layer of interosseous muscles on one side and the flexor digitorum longus and the oblique head of the adductor big toe muscle on the other. It gives off muscle branches to these muscles, to the lumbrical muscles (II, III, IV) and the flexor hallucis brevis (to its lateral head).
In addition to the listed nerves, the superficial and deep branches of the lateral plantar nerve send nerves to the capsules of the metatarsal joints and to the periosteum of the metatarsal bones and phalanges.

8. Genital nerve n. pudendus(SI-SIV), is the caudal part of the sacral plexus and is connected to it by several branches. The nerve lies under the inferior border of the piriformis muscle on the anterior surface of the coccygeus muscle; The lateral sacral vessels pass along its anterior surface in the longitudinal direction.

Nerves, arteries and veins of a woman's perineum; bottom view.

The pudendal nerve is also connected with the coccygeal plexus and with the vegetative inferior hypogastric plexus, due to which its branches take part in the innervation of the internal organs of the pelvic cavity (rectum, bladder, vagina, etc.), the external genital organs, as well as the muscles of the pelvic diaphragm: the levator ani muscle and the coccygeus muscle - and the skin of the perineal area.

Nerves, arteries and veins of the male perineum; bottom view.

The pudendal nerve emerges from the pelvic cavity, accompanied by the internal genital vessels lying medially from it, through the gap under the piriformis muscle. Next, it lies on the posterior surface of the ischial spine, goes around it and, having passed through the lesser sciatic foramen, returns to the pelvic cavity, located below the levator ani muscle, in the ischial-anal fossa, where it runs along its lateral wall, in the thickness of the internal fascia obturator muscle.

In the ischial-anal fossa, the pudendal nerve divides into its branches:

1) inferior rectal nerves, nn. rectales inferiores, are located most medially, following to the perineal part of the rectum, the external sphincter of the anus and to the skin of the anal opening;

2) perineal nerves, nn. perineates, follow along with the vessels of the perineum and are the most superficial of the terminal branches of the pudendal nerve. From the perineal nerves, muscle branches extend to the anterior parts of the external anal sphincter, to the superficial transverse perineal muscle, bulbospongiosus muscle, ischiocavernosus muscle and posterior scrotal nerves, nn. scrotales posteriores (posterior labial nerves, nn. labiates posteriores, - in women), - a superficial group of branches.

These nerves are directed to the skin of the perineum and to the skin of the posterior surface of the scrotum (labia majora in women); connect to the lower rectal nerves, as well as to the perineal branches of the posterior cutaneous nerve of the thigh;

3) dorsal nerve of the penis (dorsal nerve of the clitoris in women), n. dorsalis penis (n. dorsalis clitoridis), is the superior branch of the pudendal nerve. It follows, accompanied by the penile artery, along the inner surface of the lower branch of the ischium and pubis and, passing through the urogenital diaphragm, lies together with the dorsal penile artery on the dorsum of the penis (clitoris in women), where it branches into its terminal branches in the skin and in cavernous bodies of the penis, reaching its head (in women it reaches the labia majora and minora).

On its way, the nerve sends branches to the deep transverse muscle of the perineum, the sphincter of the urethra and the cavernous plexus of the penis (clitoris).

The sacral plexus is combined with the coccygeal plexus, called the sacrococcygeal plexus.

The sources of the plexus are the anterior branches of the IV-Vth (partially) lumbar and upper four sacral spinal nerves. When united with the coccygeal plexus, the sources include the anterior branches of the fifth sacral and coccygeal spinal nerves.

The lumbosacral trunk arises from part of the anterior branch of the IV lumbar and the entire anterior branch of the V lumbar nerves. Along the spine it descends into the pelvic cavity and on the piriformis muscle connects with the anterior branches of the sacral spinal nerves.

The sacral plexus in the form of a large triangle (stem fusion of branches) lies between the pelvic openings of the sacrum and the edge of the greater sciatic foramen, occupying part of the anterior surface of the sacrum.

Short muscle branches are the internal obturator, piriformis, quadratus muscular, superior and inferior gluteal nerves. They all go to the muscles of the same name.

The pudendal nerve, mixed, is directed to the muscles of the perineum: ischiocavernous, bulbospongiosus, transverse perineal, external anal and urethral sphincters. The cutaneous branches branch in the perineum, anus, penis, labia majora, and scrotum. They also pass to the cavernous bodies of the penis and clitoris.

Long nerves include the posterior cutaneous, sciatic with tibial and common peroneal nerves. The tibial nerves split into terminal branches: superficial and deep peroneal, plantar and dorsal nerves of the foot. The posterior cutaneous nerve branches into lateral, inferior gluteal and perineal branches and terminal branches - femoral and popliteal branches.

The sciatic nerve is the largest and longest mixed nerve in humans and contains many sensory fibers, damage to which can cause painful shock.

The sciatic nerve exits the pelvic cavity through the inferior pyriform opening; division into main branches occurs at the level of the popliteal fossa and above, forming the tibial and common peroneal nerves.

It lies superficially under the gluteal fold, which is taken into account for injuries and colds. In the posterior region of the thigh, it occupies a midline position, located deep between the hip flexor and the semitendinosus and semimembranosus muscles.

Muscular branches from it go to deep muscles pelvis, buttocks and posterior thigh area. On the buttock and pelvis there are the internal obturator, twin, and quadratus muscles. In the posterior region of the thigh lie the semitendinosus and semimembranosus muscles, the long head of the biceps muscle and rear end adductor magnus muscle.

The tibial nerve is one of the main branches of the sciatic nerve. In the popliteal fossa it lies in the middle and superficially, below it is the popliteal vein, and below it is the popliteal artery (mnemonic word “Neva” - for remembering the syntopy of the neurovascular popliteal bundle). On the lower leg, the nerve passes through the ankle-popliteal and medial malleolar canals, where it is accompanied by the posterior tibial artery and deep veins of the same name.

The short muscular branches of the tibial nerve go to the triceps surae, popliteus and plantaris muscles, tibialis posterior, flexor digitorum longus and flexor pollicis.

Cutaneous branch - the medial cutaneous nerve of the calf, connecting with the peroneal cutaneous branch of the lateral cutaneous nerve of the calf, forms the sural nerve. Its terminal branch is the lateral cutaneous nerve of the foot and cutaneous digital branches.

The terminal branches of the tibial nerve are the medial and lateral plantar nerves, supplying the skin and muscles of the sole. The medial nerve innervates the short flexor and abductor muscles of the big toe, the short flexor of the toes, the first and second lumbrical muscles, the skin of the medial surface of the sole and the first and second fingers. The lateral nerve and its deep branch innervate the quadratus plantae muscle; the third and fourth lumbrical muscles, the skin of the sole on the lateral side and the skin of the 3rd, 4th, and 5th fingers.

Peroneal nerves - common, superficial and deep. The common one begins in the popliteal fossa and goes around the head of the fibula from the outside, where it lies close to the bone under the aponeurosis of the iliotibial tract and can be damaged by fractures, sprains and ruptures of the tract. Afterwards, the nerve in the thickness of the peroneus longus muscle divides into deep and superficial branches. In the popliteal fossa, the common peroneal nerve gives off the lateral cutaneous nerve of the calf.

The superficial peroneal nerve passes in the superior peroneal canal and splits into terminal branches: the medial dorsal cutaneous nerve with branches to 1-2 fingers, the intermediate dorsal cutaneous nerve with branches to 3-5 fingers. The nerve gives off muscle branches to the peroneus longus and brevis muscles.

The deep peroneal nerve accompanies the anterior tibial artery and its associated deep veins. It innervates the muscles: tibialis anterior, extensor digitorum longus and brevis, extensor pollicis longus and brevis, and ankle joint capsule. Cutaneous branches of the fibular - dorsal digital nerves for the 1st and 2nd fingers.