Sacral plexus: anatomy, structure and functions. Sacral plexus: structure, functions, anatomy Lumbosacral plexus

Sacral plexus(plexus sacralis) is formed on the anterior side of the sacrum and pear-

Rice. 499. Cutaneous nerves of the lower limb. Front view.

1 - anterior cutaneous branches of the femoral nerve, 2 - infrapatellar branch, 3 - saphenous nerve, 4 - superficial peroneal nerve, 5 - lateral cutaneous nerve of the thigh, 6 - femoral branch of the femoral-genital nerve, 7 - femoral cutaneous branch of the ilioinguinal nerve, 8 - cutaneous branch of the obturator nerve.

Rice. 500. Femoral and obturator nerves and their branches. Front view. Superficial muscles deleted. 1 - femoral nerve, 2 - anterior cutaneous branches of the femoral nerve, 3 - obturator nerve, 4 - femoral artery, 5 - saphenous nerve, 6 - great saphenous vein of the leg, 7 - muscular branches of the femoral nerve.

prominent muscle part of the anterior branches of the fourth and fifth lumbar nerves and the anterior branches of the first-third sacral (S I -S III) spinal nerves (Fig. 498). The short branches of the plexus end in the pelvic girdle, the long branches go to the muscles, joints, bones and skin of the free part of the lower limb.

To the short branches of the sacral plexus include the internal obturator and piriformis nerves, the nerve of the quadratus femoris muscle, as well as the upper and lower gluteal and pudendal nerves (Fig. 501).

Superior gluteal nerve(n. gluteus superior) leaves the pelvic cavity through the supragiriform foramen, goes to the gluteus minimus and medius muscles, and also gives off a branch to the tensor muscle of the fascia lata.

Inferior gluteal nerve(n. gluteus inferior) leaves the pelvic cavity through the infrapiriform foramen (together with the sciatic and pudendal nerves), innervates the gluteus maximus muscle, and also gives off a branch to the capsule of the hip joint.

Pudendal nerve(n. pudendus) leaves the pelvic cavity through the infrapiriform foramen, then goes around the sciatic spine and through the lesser sciatic foramen penetrates the ischiorectal fossa, giving off the lower rectal and perineal nerves (Fig. 502). Inferior rectal nerves(nn. rectales inferiores) innervate the external sphincter of the anus and the skin of the anal area. Perineal nerves(nn. perineales) innervate the muscles and skin of the perineum and scrotum in men or the labia majora in women. The terminal branch of the pudendal nerve is dorsal nerve of the penis (clitoris)(n. dorsalis penis, s. clitoridis), which gives branches to the cavernous bodies, the head of the penis (clitoris), the skin of the penis in men, the labia majora and minora (in women), as well as branches to the deep transverse muscle perineum and urethral sphincter.

To the long branches of the sacral plexus include the posterior cutaneous nerve of the thigh and the sciatic nerve (Fig. 501).

Posterior cutaneous nerve of the thigh(n. cutaneus femoris posterior) leaves the pelvic cavity through the infrapiriform foramen and goes down next to the sciatic nerve, gives off inferior nerves of the buttocks(nn. dunium inferiores), which innervate the skin of the lower part gluteal region, And perineal nerves(rr. perineales) to the skin of the perineum. Next, the posterior cutaneous nerve of the thigh goes down and pierces fascia lata and branches in the skin of the posteromedial side of the thigh up to the popliteal fossa (Fig. 503).

Sciatic nerve(n. ischiadicus) exits the pelvic cavity through the infrapiriform foramen along with the inferior gluteal, pudendal nerves, posterior cutaneous nerve of the thigh and internal pudendal artery, along the posterior side of the adductor magnus muscle. At the level of the upper angle of the popliteal fossa or above, the sciatic nerve is divided into the tibial and common peroneal nerves (Fig. 504). Muscle branches extend from the sciatic nerve to the obturator internus, gemellus, quadratus femoris, semitendinosus, semimembranosus, long head of the biceps femoris, and posterior portion of the adductor magnus.

Tibial nerve(n. tibialis) descends vertically downwards, goes under the soleus muscle into the tibial-popliteal canal. Behind the medial malleolus, this nerve divides into its terminal branches - the medial and lateral plantar nerves (Fig. 505). The tibial nerve gives off muscle branches to the triceps surae muscle, to the long flexor muscles of the digitorum and thumb feet, to the plantar and hamstring muscles. Sensory branches of the tibial nerve go to the capsule knee joint, interosseous membrane of the leg, ankle joint, bones of the leg. The major sensory branch of the tibial nerve is medial cutaneous nerve of the calf(n. cutaneus surae medialis), which pierces the fascia and exits under the skin, where it connects with the lateral cutaneous nerve of the calf (from the common peroneal nerve). When these two nerves connect, it forms sural nerve(n. suralis), which

Rice. 501. Superior and inferior gluteal nerves. Posterior cutaneous nerve of the thigh and sciatic nerve. Back view. The gluteus maximus muscle is cut and turned upward, part of the gluteus medius gluteal muscle deleted.

1 - superior gluteal nerve, 2 - sciatic nerve, 3 - inferior nerve of the buttock, 4 - posterior cutaneous nerve of the thigh, 5 - inferior gluteal nerve.

Rice. 502. The pudendal nerve and its branches in the male perineum. View from below.

1 - pudendal nerve, 2 - internal pudendal artery, 3 - anus, 4 - dorsal nerve of the penis, 5 - artery of the bulb of the penis, 6 - bulbospongiosus muscle, 7 - posterior scrotal nerves, 8 - ischiocavernosus muscle, 9 - external anal sphincter, 10 - levator ani muscle, 11 - gluteus maximus muscle, 12 - inferior rectal artery, 13 - inferior rectal nerves.

Rice. 503. Cutaneous nerves of the gluteal region and the free part of the lower limb. Back view.

1 - superior nerves of the buttock, 2 - middle nerves of the buttock, 3 - lower branches of the buttock, 4 - posterior cutaneous nerve of the thigh, 5 - medial cutaneous nerve of the calf, 6 - lateral cutaneous nerve of the calf, 7 - sural nerve.

Rice. 504. Tibial and common peroneal nerves. Back view. Triceps tibia removed.

1 - sciatic nerve, 2 - tibial nerve, 3 - common peroneal nerve, 4 - medial calf cutaneous nerve, 5 - lateral calf cutaneous nerve, 6 - sural nerve.

innervates the skin of the lateral side of the dorsum of the foot (Fig. 504).

Medial plantar nerve(n. plantaris medialis) on the foot runs along the medial plantar groove and gives off muscle branches to the flexor digitorum brevis and the medial head of the flexor hallucis, to the abductor hallucis muscle, as well as to the two medial lumbrical muscles (Fig. 505 ). The medial plantar nerve gives off own plantar digital nerve(n. digitalis plantaris proprius) to the skin of the medial edge of the foot and big toe, as well as three common plantar digital nerves(nn. digitales plantares communes), each of which is divided into two proper plantar digital nerves(nn. digitales plantares proprii), innervating the skin of the first to fourth toes facing each other.

Lateral plantar nerve(n. plantaris lateralis) goes in the lateral plantar groove, gives branches to the quadratus plantar muscle, to the short flexor of the little finger and to the muscle opposing the little finger, to the third and fourth lumbrical muscles, to the interosseous muscles, to the muscle that adducts the big toe , and to the lateral head of the flexor hallucis brevis. The lateral plantar nerve also innervates the skin of the lateral side of the little toe and the sides of the fourth and fifth toes facing each other.

Common peroneal nerve goes obliquely downwards and laterally, giving branches to the knee and tibiofibular joints, to the short head of the biceps femoris muscle. Its branch is lateral cutaneous nerve of the calf(n. cutaneus surae lateralis), which innervates the skin of the lateral side of the leg, and at the level of the middle of the leg it exits under the skin and connects with the medial cutaneous nerve of the calf (forms the sural nerve).

The common peroneal nerve near the lateral angle of the popliteal fossa is divided into the superficial and deep peroneal nerves (Fig. 506).

Rice. 505. Plantar nerves and their branches. The muscles of the sole of the foot are partially removed. 1 - common digital nerves, 2 - plantar metatarsal arteries, 3 - medial plantar nerve, 4 - lateral plantar nerve, 5 - medial plantar artery, 6 - posterior tibial artery, 7 - calcaneal branch, 8 - lateral plantar artery, 9 - plantar arterial arch, 10 - proper digital nerves.

Rice. 506. Common peroneal nerve and its branches. Front and side views.

1 - common peroneal nerve, 2 - superficial peroneal nerve, 3 - peroneus longus, 4 - extensor digitorum longus, 5 - fascia of the leg, 6 - superficial peroneal nerve, 7 - intermediate dorsal cutaneous nerve, 8 - sural nerve, 9 - lateral dorsal cutaneous nerve, 10 - dorsal digital nerves of the foot, 11 - deep peroneal nerve, 12 - dorsal artery of the foot, 13 - medial dorsal cutaneous nerve, 14 - anterior tibial muscle, 15 - anterior tibial artery, 16 - deep peroneal nerve, 17 - muscle branches, 18 - knee joint network.

Superficial peroneal nerve(n. peroneus superficialis) goes laterally and downward in the superior musculofibular canal, innervates the short and long peroneal muscles. At the border of the middle and lower third of the leg, the nerve leaves the superior musculofibular canal and goes to the dorsum of the foot, where it divides into the medial and intermediate dorsal cutaneous nerves. Medial dorsal cutaneous nerve(n. cutaneus dorsalis medialis) innervates the skin of the medial edge of the dorsum of the foot and the skin of the second and third toes facing each other. Intermediate dorsal cutaneous nerve(n. cutaneus dorsalis intermedius) innervates the skin of the superolateral side of the dorsum of the foot, as well as the sides of the third to fifth toes facing each other (dorsal digital nerves of the foot, nn. digitales dorsales pedis).

Deep peroneal nerve(n. fibularis, profundus, s. fibularis profundus) passes through the hole in the anterior intermuscular septum of the leg, descends along the front side of the interosseous membrane of the leg and gives branches to the anterior tibial and other muscles of the leg (Fig. 506). The nerve on the dorsum of the foot innervates short muscles, which extend the fingers and thumb, gives off sensitive branches to the ankle joint, to the joints and bones of the foot.

Coccygeal plexus(plexus coccygeus) is located on the anterior side of the coccygeus muscle and on the sacrococcygeal ligament. Originating from the coccygeal plexus antococcygeal nerves(nn. anococcygei) innervate the skin in the area of the coccyx and anus. Muscular branches(rami musculares) of this plexus innervate the coccygeus muscle and the posterior part of the levator ani muscle.

Autonomic (autonomic) nervous system

Autonomic (autonomic) nervous system(systema nervosum autonomicum) is a part of the nervous system that controls the functions of internal organs, glands, heart and blood vessels, exercises an adaptive-trophic effect on all human organs, and maintains the constancy of the internal environment of the body (homeostasis). The functions of the autonomic (autonomic) nervous system are not controlled by consciousness, but they are subordinate to the spinal cord and brain.

The autonomic (autonomous) system is divided into central and peripheral sections. TO central department include: parasympathetic autonomic nuclei of the oculomotor, facial, glossopharyngeal and vagus cranial nerves lying in the brain stem (midbrain, pons and medulla oblongata); parasympathetic sacral nuclei (nuclei parasympathici sacrales), located in the gray matter of the three sacral segments of the spinal cord (S II - S iv), as well as the autonomic (sympathetic) thoracic nucleus (nucleus thoracicus), located in the lateral column of the eighth cervical, all thoracic and two upper lumbar segments of the spinal cord (C IIX, Th I - Th XII, L I - L II).

TO peripheral department The autonomic (autonomic) nervous system includes autonomic (autonomic) nerves, branches and nerve fibers emerging from the brain and spinal cord, autonomic (autonomous) visceral nerve plexuses, nodes of the autonomic (autonomous, visceral) plexuses, autonomic fibers (parasympathetic and sympathetic), going from the vegetative nodes to the organs and tissues of the human body, nerve endings involved in autonomic reactions.

Autonomic (autonomous) nerve fibers emerging from the spinal cord and brain as part of the roots of the spinal and cranial nerves, and then their branches, are formed by processes of neurons in the lateral horns of the spinal cord or autonomic nuclei of the cranial nerves. The axons of these neurons (efferent) are directed to the periphery to the nodes of the autonomic nerve plexuses, on the cells of which these fibers end. The processes of cells located in the vegetative nodes are sent to organs, tissues, blood and lymphatic vessels for their innervation. The path of autonomic innervation from the brain to the working organ consists

Rice. 507. Autonomic reflex arc.

1 - posterior root of the spinal nerve, 2 - intermediate lateral nucleus of the lateral horn of the spinal cord, 3 - preganglionic (prenodular) fibers of the intercalary neuron (as part of the anterior root of the spinal nerve), 4 - spinal ganglion, 5 - spinal nerve, 6 - white connecting branch, 7 - node of the sympathetic trunk, 8 - gray connecting branch, 9 - postganglionic (post-nodal) nerve fibers of the effector neuron as part of the spinal nerve, 10 - postganglionic (post-nodal) fibers of the effector neuron (as part of the splanchnic nerve), 11 - nerve node autonomic plexus, 12 - postganglionic (post-nodal) nerve fibers of the effector neuron (as part of the visceral and choroid plexuses), 13 - postganglionic fibers to the blood vessel, 14 - blood vessel, 15 - postganglionic (post-nodal) nerve fibers (to the sweat glands of the skin, muscles hair and to blood vessels).

of two neurons (Fig. 507). The axons of a neuron extending from the vegetative nucleus in the brain to the vegetative ganglion in the periphery are called prenodal (preganglionic) nerve fibers(neurofibrae preganglionares). The axons of neurons whose bodies are located in the peripheral vegetative node are called postnodal (postganglionic) nerve fibers(neurofibrae postganglionares). Autonomic nerve fibers are part of the cranial and spinal nerves and their branches.

Based on the topography of the autonomic nuclei and nodes, differences in the length of the fibers of the first and second neurons of the efferent pathway, as well as the characteristics of the functions, the autonomic nervous system is divided into sympathetic and parasympathetic parts.

The posterior branches, in turn, are divided into internal and external. Internal branches innervate the lower segments deep muscles back and end with cutaneous branches in the sacral region, closer to the midline. The external branches of the I-III sacral spinal nerves are directed downward and are called the middle cutaneous nerves of the buttocks (pp. clunium medii), innervating the skin of the middle parts of the gluteal region.

The anterior branches of the sacral nerves, emerging through the anterior sacral foramina onto the pelvic surface of the sacral bone, form the sacral plexus.

Sacral plexus (plexus sacralis) consists of loops formed by the anterior branches of the lumbar and sacral spinal nerves (L5-S2 and partially L4 and S3). The sacral plexus, which has numerous connections with the lumbar plexus, is located in front of the sacrum, on the anterior surface of the piriformis and partly coccygeal muscles on the sides of the rectum and goes down to the greater sciatic notch (incisure ischiadica major), through which the peripheral nerves formed in the sacral plexus leave the pelvic cavity.

The muscular branches of the sacral plexus innervate the following muscles: a) piriformis muscle (t. piriformis), which is located between the anterior surface of the sacrum and inner surface greater trochanter of the femur. Crossing the greater sciatic foramen, this muscle divides it into supra- and infrapiriform parts, through which vessels and nerves pass; b) internal obturator muscle (i.e. obturatorius internus), located inside the pelvis; c) upper and outer muscles of the twins (t. gemelles superior et inferior)"., G) quadratus femoris muscle. All of these muscles externally rotate the hip. To determine their strength, the following tests can be performed: 1) the patient, lying on his stomach with his lower leg bent at a right angle, is asked to move his lower leg inward, while the examiner resists this movement; 2) the patient lying on his back is asked to rotate his legs outward, while the examiner resists this movement.

Superior gluteal nerve (n. gluteus superior, L4-S1) - motor, it innervates gluteus medius and minimus muscles(mm. glutei medius et minimus), tensor fascia lata(m. tensor fasciae latae), the contraction of which leads to hip abduction. Damage to the nerve causes difficulty in hip abduction, flexion and internal rotation. With bilateral damage to the superior gluteal nerve, the patient's gait becomes like a duck's - the patient seems to waddle from one foot to the other when walking.

Lower gluteal nerve (p. gluteus inferior, L5-S2) is motor, innervates gluteus maximus muscle (i.e. gluteus maximus), extending the hip, and with a fixed hip, tilting the pelvis backward. If the inferior gluteal nerve is damaged, hip extension is difficult. If a standing patient bends over, then it is difficult for him to straighten his torso. The pelvis in such patients is fixed tilted forward, as a result of which compensated lordosis develops. lumbar region spine. Patients find it difficult to climb stairs, jump, or get out of a chair.

Posterior cutaneous nerve of the thigh (p, cutaneus femoris posterior, S1-S3)- sensitive. It exits through the infrapiriform foramen behind the sciatic nerve, with which it has anastomoses. Then it passes between the ischial tuberosity and the greater trochanter, goes down and innervates the skin back surface thighs, including the popliteal fossa. The inferior cutaneous nerves of the buttock (ll.) depart from the posterior cutaneous nerve of the thigh. clinium inferiores), perineal nerves (rr. perineales), which provide sensitivity to the corresponding skin areas.

Sciatic nerve (n. ischiadicus, L4-S3/) - mixed; the largest of peripheral nerves. Its motor part innervates most of the muscles of the leg, in particular all the muscles of the lower leg and foot. Even before exiting the thigh, the sciatic nerve gives off motor branches to biceps femoris muscle (biceps femoris), semitendinosus muscle (semitendinosus) And semimembranosus muscle (t. semimembranosus), bending the lower leg at the knee joint and rotating it inward. In addition, the sciatic nerve innervates adductor magnus muscle (i.e. adductor magnus), which flexes the lower leg, rotating it outward.

Having reached the level of the thigh, the sciatic nerve passes along its posterior side and, approaching the popliteal fossa, divides into two branches - the tibial and peroneal nerves.

Tibial nerve (n. tibialis, L4-S3) is a direct continuation of the sciatic nerve. It runs down the middle of the popliteal fossa along the back of the shin to the inner ankle. Motor branches of the tibial nerve innervate the triceps surae muscle(/I. triceps surae), consisting of the soleus muscle (i.e. soleus) and calf muscle. The triceps surae muscle flexes the lower leg at the knee joint and the foot at the ankle. In addition, the tibial nerve innervates popliteus muscle (i.e. popliteus), involved in flexing the tibia at the knee joint and rotating it inward; posterior tibial muscle (t. tibialis posterior), adducting and elevating the inner edge of the foot; flexor digitorum longus (i.e. flexor digitorum longus), bending the nail phalanges of the II-V fingers; flexor pollicis longus(m. flexor hallucis longus), the contraction of which causes flexion of the first toe.

At the level of the popliteal fossa, it departs from the tibial nerve medial cutaneous nerve of the leg (n. cutaneus surae medialis), the branches of which innervate the skin of the posterior surface of the leg (Fig. 8.12). In the lower third of the leg, this cutaneous nerve anastomoses with the branch of the lateral cutaneous nerve of the leg, which arises from the peroneal nerve, and is then called sural nerve (p. suralis) descends along the lateral edge of the calcaneal (Achilles) tendon, wraps around the back of the outer ankle. Here it departs from the sural nerve lateral calcaneal branches (rr. calcanei laterales), innervating the skin of the lateral part of the heel. Next, the sural nerve goes forward to the lateral surface of the foot called lateral dorsal cutaneous nerve (n. cutaneus dorsalis lateralis) and innervates the skin of the dorsolateral surface of the foot and little toe.

Slightly above the level of the medial malleolus, they extend from the tibial nerve medial calcaneal branches (rr. rami calcanei mediates).

Having gone down to ankle joint, tibial nerve passes at the posterior edge of the inner ankle onto the sole. On inside he calcaneus divided by final branches: medial and lateral plantar nerves.

Medial plantar nerve (n. plantaris medialis) passes under the abductor pollicis muscle, and then goes forward and divides into muscular and cutaneous branches. The muscular branches of the medial plantar nerve innervate the short flexor of the fingers (m. flexor digitorum brevis), which flexes the middle phalanges of the II-V fingers; flexor pollicis brevis (t. flexor hallucis brevis), involved in ensuring flexion of the thumb; abductor pollicis muscle (i.e. adductor hallucis), participating in the flexion of the thumb and ensuring its abduction. In addition, the own plantar digital nerves arise from the medial plantar nerve. innervating the skin of the medial and plantar surface of the big toe, as well as the common plantar digital nerves (pp. digitales plantares communis), innervating the skin of the first three interdigital spaces and the plantar surface of I-III, as well as the medial side of the IV fingers. From the I and II common plantar nerves, muscle branches also extend to the I and II lumbrical muscles, flexing the main and extending the remaining phalanges of the I, II and partly III toes.

Lateral plantar nerve (p. plantaris lateralis) directed along the plantar side of the foot forward and outward, gives off branches innervating the quadratus plantae muscle (t. quadratusplantae), promoting finger flexion; flexor digitorum brevis (i.e. abductor digiti minimi), abductor and flexor of the little finger. After these branches depart, the lateral plantar nerve is divided into deep and superficial branches.

Deep branch (m. profundus) penetrates deep into the plantar surface of the foot and innervates the adductor pollicis muscle (i.e. adductor hallucis) and flexor digitorum brevis (i.e. flexor digiti minimi brevis) and III-IV lumbrical muscles (vol. lumbrica/es), flexing the main and extensor middle and nail phalanges of the IV, V and partly III toes, as well as the plantar and dorsal interosseous muscles (vol. inercostales plantares et dorsales), flexing the main and extending the remaining phalanges of the fingers, as well as abductor and adductor toes.

Superficial branch (ramus superficialis) lateral plantar nerve divides into common plantar digital nerves (pp. digitales plantares communis)) from which the 3 own plantar digital nerves arise (pp. digitales plantares proprii), innervating the skin of the fifth and lateral side of the fourth fingers, as well as the lateral part of the foot.

If the tibial nerve is damaged, it becomes impossible to flex the foot and its toes. As a result, the foot becomes fixed in the extension position (Fig. 8.13a), and therefore the so-called calcaneal foot (pes calcaneus) - When walking, the patient steps primarily on his heel and cannot rise on his toes. Atrophy of the small muscles of the foot leads to a claw-like position of the toes (to the development claw-shaped foot). In this case, spreading and bringing the toes together is difficult. Sensation on the lateral and plantar side of the foot is impaired.

If the sciatic or tibial nerves are damaged, the heel (Achilles) reflex decreases or disappears.

Common peroneal nerve (n. peroneus communis, L4-S1)- the second of the main branches of the sciatic nerve. The cutaneous external nerve of the calf arises from the common peroneal nerve (p. cutaneus surae lateralis), branching on the lateral and posterior surfaces of the leg. On the lower third of the leg, this nerve anastomoses with the cutaneous medial nerve of the leg, which is a branch of the tibial nerve, thereby forming the sural nerve (p. suralis).

Behind the head fibula The common peroneal nerve is divided into two parts: the superficial and deep peroneal nerves (n. peroneus profundus).

Rice. 8.13.“Heel” foot with damage to the tibial nerve (a);

“dropping” foot with damage to the peroneal nerve (b).

Superficial peroneal nerve (p. peroneus superflcialis) goes down the anterior outer surface of the leg, gives branches to the long and short peroneal muscles (vol. peronei longus et brevis), abducting and lifting the outer edge of the foot and at the same time flexing it. In the middle third of the leg, this nerve exits under the skin and divides into the medial and intermediate dorsal cutaneous nerves.

Medial dorsal cutaneous nerve (nervus cutaneus dorsalis medialis) is divided into two branches: medial and lateral. The first of them is directed to the medial edge of the foot and big toe, the second - to the skin of the dorsal surface of the halves of the second and third fingers facing each other.

Intermediate dorsal cutaneous nerve (a. cutaneus dorsalis intermedius) gives off sensory branches to the skin of the knees and dorsum of the foot and is divided into medial and lateral branches. The medial branch is directed to the dorsal surface of the halves of the third and fourth fingers facing each other.

Deep peroneal nerve (a. peroneus profundus) innervates the tibialis anterior muscle (m. tibialis anterior), which extends the foot and elevates its inner edge; extensor digitorum longus (i.e. extensor digitorum longus), extensor foot, II-V fingers, as well as abductor and pronating foot; extensor pollicis brevis (i.e. extensor hallucis longus), extending and supinating the foot, as well as extending the big toe; extensor pollicis brevis (i.e. extensor digitorum brevis), extending the thumb and deflecting it to the lateral side.

If the peroneal nerve is damaged, it becomes impossible to extend the foot and toes and turn the foot outward. As a result, the foot hangs down, being slightly rotated inwards, its toes bent at the joints of the main phalanges (Fig. 8.136). Leaving the foot in this position for a long time can lead to contracture. Then they talk about development horse foot (pes equinus). When the peroneal nerve is damaged, a characteristic gait develops. Avoiding contact of the back surface of the fingers with the floor, the patient, when walking, raises his leg high, bending it at the hip and knee joints more than usual. The foot touches the floor first with the toe, and then with the main surface of the sole. This gait is called peroneal, equine, cockerel and is often denoted by the French word steppage(steppage). A patient with damage to the peroneal nerve cannot stand on his heels, straighten the foot and toes, or turn the foot outward.

With total damage to the sciatic nerve, naturally, the function of the tibial and peroneal nerves simultaneously suffers, which is manifested by paralysis of the foot muscles, loss of the reflex from the heel tendon (calcaneal or Achilles reflex). In addition, the flexion of the lower leg is impaired. Sensitivity in the lower leg remains intact only along the anterior internal surface in the zone of innervation of the saphenous nerve of the saphenus. With high damage to the sciatic nerve, sensory impairment also manifests itself on the back of the thigh.

If a pathological process irritates the sciatic nerve, then this is primarily manifested by severe pain, as well as pain on palpation along the nerve, especially distinct in the so-called Balle points: between the ischial tuberosity and the greater trochanter, in the popliteal fossa, behind the head of the fibula.

The sacral spinal nerves arise from the sacral segments of the spinal cord at the level of the body of the first lumbar vertebra and descend down into the sacral canal, at the level of which, in the area of the intervertebral foramina of the sacrum, the sacral spinal nerves are formed due to the fusion of the anterior and posterior spinal roots. These nerves are divided into anterior and posterior branches, leaving the sacral canal through the intervertebral foramina of the sacrum, with the anterior branches extending to the pelvic surface of the sacrum (into the pelvic cavity), and the posterior branches to its dorsal surface. The branches of the V sacral spinal nerve exit the sacral canal through the sacral fissure (hiatus sacralis). The posterior branches, in turn, are divided into internal and external. The internal branches innervate the lower segments of the deep muscles of the back and end with cutaneous branches in the sacrum, closer to the midline. The external branches of the I-III sacral spinal nerves are directed downward and are called the middle cutaneous nerves of the buttocks (clunium medii), innervating the skin of the middle parts of the gluteal region. The anterior branches of the sacral nerves, emerging through the anterior sacral foramina onto the pelvic surface of the sacral bone, form the sacral plexus. The sacral plexus (plexus sacralis) consists of loops formed by the anterior branches of the lumbar and sacral spinal nerves (L5-S2 and partially L4 and S3). The sacral plexus, which has numerous connections with the lumbar plexus, is located in front of the sacrum, on the anterior surface of the piriformis and partly coccygeal muscles on the sides of the rectum and is directed down to the greater sciatic notch (incisure ischiadica major), through which the pelvic cavity leaves the sacral plexus. peripheral nerves. The muscular branches of the sacral plexus innervate the following muscles: a) the piriformis muscle (i.e. piriformis), which is located between the anterior surface of the sacrum and the inner surface of the greater trochanter of the femur. Crossing the greater sciatic foramen, this muscle divides it into supra- and infrapiriform parts, through which vessels and nerves pass; b) the internal obturator muscle (i.e. obturatorius internus), located inside the pelvis; c) the superior and external muscles of the twins (t. gemelles superior et inferior)., d) quadratus femoris muscle (t. quadratics femoris). All of these muscles externally rotate the hip. To determine their strength, the following tests can be performed: 1) the patient, lying on his stomach with his lower leg bent at a right angle, is asked to move his lower leg inward, while the examiner resists this movement; 2) the patient lying on his back is asked to rotate his legs outward, while the examiner resists this movement. The superior gluteal nerve (p. gluteus superior, L4-S1) is motor, it innervates the gluteus medius and minimus muscles (mm. glutei medius et minimus), the tensor fasciae latae (m. tensor fasciae latae), the contraction of which leads to hip abduction. Damage to the nerve causes difficulty in hip abduction, flexion and internal rotation. With bilateral damage to the superior gluteal nerve, the patient's gait becomes like a duck's - the patient seems to waddle from one foot to the other when walking. The lower gluteal nerve (p. gluteus inferior, L5-S2) is motor, innervates the gluteus maximus muscle (gluteus maximus), which extends the hip, and with a fixed hip, tilts the pelvis backward. If the inferior gluteal nerve is damaged, hip extension is difficult. If a standing patient bends over, then it is difficult for him to straighten his torso. The pelvis in such patients is fixed tilted forward, as a result of which compensated lordosis develops in the lumbar spine. Patients find it difficult to climb stairs, jump, or get out of a chair. The posterior cutaneous nerve of the thigh (p, cutaneus femoris posterior, S1-S3) is sensitive. It exits through the infrapiriform foramen behind the sciatic nerve, with which it has anastomoses. Then it passes between the ischial tuberosity and the greater trochanter, goes down and innervates the skin of the back of the thigh, including the popliteal fossa. From the posterior cutaneous nerve of the thigh depart the lower cutaneous nerves of the buttock (ll. clinium inferiores), perineal nerves (rr. perineales), which provide sensitivity to the corresponding skin zones. Sciatic nerve (p. ischiadicus, L4-S3/) - mixed; the largest of the peripheral nerves. Its motor part innervates most of the muscles of the leg, in particular all the muscles of the lower leg and foot. Even before entering the thigh, the sciatic nerve gives off motor branches to the biceps femoris muscle, the semitendinosus muscle and the semimembranosus muscle, which flex the tibia at the knee joint and rotate it inward. In addition, the sciatic nerve innervates the adductor magnus muscle, which flexes the lower leg, rotating it outward. Having reached the level of the thigh, the sciatic nerve passes along its posterior side and, approaching the popliteal fossa, divides into two branches - the tibial and peroneal nerves. The tibial nerve (n. tibialis, L4—S3) is a direct continuation of the sciatic nerve. It runs down the middle of the popliteal fossa along the back of the shin to the inner ankle. The motor branches of the tibial nerve innervate the triceps surae muscle (triceps surae), consisting of the soleus muscle and the gastrocnemius muscle. The triceps surae muscle flexes the lower leg at the knee joint and the foot at the ankle. In addition, the tibial nerve innervates the popliteus muscle, which is involved in flexing the tibia at the knee joint and rotating it inward; tibialis posterior muscle, which adducts and elevates the inner edge of the foot; flexor digitorum longus (flexor digitorum longus), which flexes the nail phalanges of the II-V fingers; long flexor of the big toe (m. flexor hallucis longus), the contraction of which causes flexion of the first toe. At the level of the popliteal fossa, the medial cutaneous nerve of the leg (n. cutaneus surae medialis) departs from the tibial nerve, the branches of which innervate the skin of the posterior surface of the leg (Fig. 8.12). In the lower third of the leg, this cutaneous nerve anastomoses with the branch of the lateral cutaneous nerve of the leg, arising from the peroneal nerve, and then, under the name of the sural nerve (n. suralis), descends along the lateral edge of the calcaneal (Achilles) tendon, bends around the back of the outer ankle . Here, its lateral calcaneal branches (rr. calcanei laterales) depart from the sural nerve, innervating the skin of the lateral part of the heel. Next, the sural nerve goes forward to the lateral surface of the foot under the name of the lateral dorsal cutaneous nerve (n. cutaneus dorsalis lateralis) and innervates the skin of the dorsolateral surface of the foot and little toe. Somewhat above the level of the medial malleolus, the medial calcaneal branches (rr. rami calcanei mediates) depart from the tibial nerve. Having descended to the ankle joint, the tibial nerve passes at the posterior edge of the inner malleolus to the sole. On the inside of the calcaneus, it is divided into terminal branches: the medial and lateral plantar nerves. The medial plantar nerve (p. plantaris medialis) passes under the abductor pollicis muscle, and then goes forward and divides into muscle and cutaneous branches. The muscular branches of the medial plantar nerve innervate the short flexor of the fingers (m. flexor digitorum brevis), which flexes the middle phalanges of the II-V fingers; short flexor of the thumb (i.e. flexor hallucis brevis), involved in ensuring flexion of the thumb; the muscle that abducts the thumb (i.e. adductor hallucis), which is involved in flexion of the thumb and ensures its abduction. In addition, the own plantar digital nerves (digitales plantares proprii) depart from the medial plantar nerve, innervating the skin of the medial and plantar surface of the big toe, as well as the common plantar digital nerves (digitales plantares communis), innervating the skin of the first three interdigital spaces and the plantar surface of I-III, as well as the medial side of IV fingers. From the I and II common plantar nerves, muscle branches also extend to the I and II lumbrical muscles, flexing the main and extending the remaining phalanges of the I, II and partly III toes. The lateral plantar nerve (n. plantaris lateralis) is directed along the plantar side of the foot forward and outward, giving off branches that innervate the quadratus plantae muscle, which promotes flexion of the toes; short flexor of the fifth finger (i.e. abductor digiti minimi), abductor and flexor of the little finger. After these branches arise, the lateral plantar nerve divides into deep and superficial branches. The deep branch (g. profundus) penetrates deep into the plantar surface of the foot and innervates the adductor hallucis muscle and the short flexor of the fifth finger (flexor digiti minimi brevis) and III-IV lumbrical muscles (t. lumbrica/es), flexing the main and extending middle and nail phalanges of the IV, V and partly III toes, as well as the plantar and dorsal interosseous muscles (t. inercostales plantares et dorsales), flexing the main and extending the remaining phalanges of the fingers, as well as abductors and adductor toes. The superficial branch (ramus superficialis) of the lateral plantar nerve is divided into common plantar digital nerves (digitales plantares communis) from which 3 own plantar digital nerves (digitales plantares proprii) arise, innervating the skin of the V and lateral side of the IV fingers, as well as the lateral part of the foot. If the tibial nerve is damaged, it becomes impossible to flex the foot and its toes. As a result, the foot becomes fixed in the extension position (Fig. 8.13a), and therefore the so-called calcaneal foot (pes calcaneus) develops - the patient steps mainly on the heel while walking, he cannot rise on his toes. Atrophy of the small muscles of the foot leads to a claw-shaped position of the toes (the development of a claw-shaped foot). In this case, spreading and bringing the toes together is difficult. Sensation on the lateral and plantar side of the foot is impaired. If the sciatic or tibial nerves are damaged, the heel (Achilles) reflex decreases or disappears. The common peroneal nerve (p. peroneus communis, L4-S1) is the second of the main branches of the sciatic nerve. The cutaneous external nerve of the calf (n. cutaneus surae lateralis) departs from the common peroneal nerve, branching on the lateral and posterior surfaces of the leg. On the lower third of the leg, this nerve anastomoses with the cutaneous medial nerve of the leg, which is a branch of the tibial nerve, and the sural nerve (n. suralis) is formed. Rice. 8.13. “Heel” foot with damage to the tibial nerve (a); “dropping” foot with damage to the peroneal nerve (b). Behind the head of the fibula, the common peroneal nerve is divided into two parts: the superficial and deep peroneal nerves (p. peroneus profundus). The superficial peroneal nerve (p. peroneus superflcialis) is directed down the anterior outer surface of the leg, gives off branches to the long and short peroneal muscles (t. peronei longus et brevis), which abduct and elevate the outer edge of the foot and at the same time perform its flexion. In the middle third of the leg, this nerve exits under the skin and divides into the medial and intermediate dorsal cutaneous nerves. The medial dorsal cutaneous nerve (nervus cutaneus dorsalis medialis) is divided into two branches: medial and lateral. The first of them is directed to the medial edge of the foot and big toe, the second - to the skin of the dorsal surface of the halves of the second and third fingers facing each other. The intermediate dorsal cutaneous nerve (a. cutaneus dorsalis intermedius) gives off sensory branches to the skin of the knees and dorsum of the foot and is divided into medial and lateral branches. The medial branch is directed to the dorsal surface of the halves of the third and fourth fingers facing each other. The deep peroneal nerve (a. peroneus profundus) innervates the tibialis anterior muscle (m. tibialis anterior), which extends the foot and elevates its inner edge; long extensor digitorum (i.e. extensor digitorum longus), which extends the foot, II-V fingers, as well as the abductor and pronating foot; short extensor hallucis longus (extensor hallucis longus), which extends and supinates the foot, as well as extensor hallucis longus; short extensor pollicis (i.e. extensor digitorum brevis), which extends the thumb and deflects it to the lateral side. If the peroneal nerve is damaged, it becomes impossible to extend the foot and toes and turn the foot outward. As a result, the foot hangs down, being slightly rotated inwards, its toes bent at the joints of the main phalanges (Fig. 8.136). Leaving the foot in this position for a long time can lead to contracture. Then they talk about the development of the equine foot (pes equinus). When the peroneal nerve is damaged, a characteristic gait develops. To avoid contact of the back surface of the fingers with the floor, the patient raises his leg high when walking, bending it at the hip and knee joints more than usual. The foot touches the floor first with the toe, and then with the main surface of the sole. This type of gait is called peroneal, equine, or cock-tire and is often denoted by the French word steppage. A patient with damage to the peroneal nerve cannot stand on his heels, straighten the foot and toes, or turn the foot outward. With total damage to the sciatic nerve, naturally, the function of the tibial and peroneal nerves suffers at the same time, which is manifested by paralysis of the foot muscles, loss of the reflex from the heel tendon (calcaneal or Achilles reflex). In addition, the flexion of the lower leg is impaired. Sensitivity in the lower leg remains intact only along the anterior internal surface in the zone of innervation of the saphenous nerve of the saphenus. With high damage to the sciatic nerve, sensory impairment also manifests itself on the back of the thigh. If the pathological process irritates the sciatic nerve, then this is primarily manifested by severe pain, as well as pain on palpation along the nerve, especially distinct in the so-called Balle points: Fig. 8.14. Lassga symptom (first and second phases). Explanation in the text. between the ischial tuberosity and the greater trochanter, in the popliteal fossa, behind the head of the fibula. The Lasègue symptom (Fig. 8.14), which belongs to the group of tension symptoms, has important diagnostic significance in cases of damage to the sciatic nerve. It is checked with the patient lying on his back with his legs straightened. If you try to bend the patient’s leg, which is extended at the knee joint, at the hip joint, then tension in the sciatic nerve will occur, accompanied by pain that limits the possible volume of movement performed; in this case, it can be measured in angular degrees and thus objectify the angle at which it is possible raise your leg above the horizontal plane. After bending the leg at the knee joint, the tension of the sciatic nerve decreases, and at the same time the pain reaction decreases or disappears. With damage to the sciatic nerve containing a large number of autonomic fibers and its branch - the tibial nerve, as well as with damage to the median nerve on the arm, the pain often has a causal tinge; Severe tissue trophic disorders are also possible, in particular trophic ulcers (Fig. 8.15).

Table of contents of the topic “Sacral plexus, plexus sacralis.”:

Sacral plexus, plexus sacralis. Short branches of the sacral plexus

Sacral plexus, plexus sacralis, - the most significant of all plexuses, is composed of the anterior branches of the IV (lower part) and V of the lumbar nerve and the same branches of the four sacral nerves (SI-SIV), emerging from the anterior openings of the sacrum. The proximity of numerous plexus bundles to the sacroiliac joint causes different localization and irradiation of pain in diseases of this joint. The nerves of the plexus, connecting with each other, form a thick trunk of the sciatic nerve, emerging through the foramen infrapiriforme from the pelvic cavity. The branches arising from the sacral plexus can be divided into short and long.

The former branch in the region of the lower limb girdle, and the latter supply the entire lower limb, with the exception of that part of it that is supplied with branches of the lumbar plexus.

Short branches

1. Rami musculares for m. piriformis (from SI and SII), m. obturatorius interims with mm. gemelli and quadratus femoris (from LIV, Lv, SI and SII), for mm. levator ani et coccygeus.

2. N. gluteus superior(L.v and Lv and from SI) comes out through foramen suprapiriforme from the pelvis together with the artery of the same name and then spreads to m. gluteus medius, m. gluteus minimus and m. tensor fasciae latae.

3. N. gluteus inferior(Lv, SI SII), emerging through the foramen infrapiriforme, supplies its branches to m. gluteus maximus and the capsule of the hip joint.

4. N. pudendus (SI - SIV), leaving through foramen infrapiriforme, goes back into the pelvis through the foramen ischiadicum minus. Next, n. pudendus, together with the sonominal artery, passes along the lateral wall fossa ischiorectalis. Within the latter, nn depart from it. rectales inferiores, which supply the external sphincter, m. sphincter ani externus, and the skin in the immediate circumference of the anus. At the level of the ischial tuberosity at the posterior edge of the diaphragma urogenital n. pudendus is divided into nn. perinei and n. dorsalis penis (clitoridis). The first, going anteriorly, innervate m. ischiocavernosus, m. bulbospongiosus and m. transversus perinei superficialis, as well as the skin of the perineum. The terminal branches supply the skin of the posterior side of the scrotum (nn. scrotales posteriores) or the labia majora (nn. labiales posteriores).

N. dorsalis penis (clitoridis) accompanies in the thickness of the diaphragma urogenital a. dorsalis penis, gives branches to m. transversus perinei profundus and m. sphincter urethrae, passes to the back of the penis (or clitoris), where it spreads in the skin mainly glans penis. Composed of n. pudendus passes through a large number of vegetative fibers.

The sacral plexus (plexus sacralis) is formed by part of the anterior branch of the fourth and fifth lumbar (LIV-LV) and first-third sacral (SI-SIII) spinal nerves. The plexus is located in the pelvic cavity, directly on the fascia covering the anterior surface of the piriformis muscle. The base of the plexus corresponds to the line connecting the pelvic sacral foramina. The branches of the sacral plexus are directed to the greater sciatic foramen. There are short and long branches of the sacral plexus. Short branches end in the pelvic girdle. Long branches go to the muscles, joints, bones and skin of the free part of the lower limb.

Short branches. The short branches of the sacral plexus include the obturator internal nerve (from LIV-SII), the piriformis nerve (from SI-SII), the quadratus femoris nerve (from LIV-SII, going to the muscles of the same name, as well as the superior and inferior gluteal and pudendal nerves.

The superior gluteal nerve (n. gluteus superior) is formed by fibers of the anterior branches of the fourth and fifth lumbar (LIV-LV) and first sacral (SI) spinal nerves. Together with the artery of the same name, the nerve leaves the pelvic cavity through the supragiriform foramen. Upper branch This nerve goes forward to the gluteus minimus muscle and innervates it. The inferior branch of the superior gluteal nerve passes between the gluteus minimus and medius muscles, innervates them, and also gives off a branch to the tensor fascia lata muscle.

The inferior gluteal nerve (n. gluteus inferior) consists of fibers of the anterior branches of the fifth lumbar (LV) and the first and second sacral (SI-SII) spinal nerves. The nerve exits the pelvic cavity through the infrapiriform foramen along with the artery of the same name. With fan-shaped diverging short branches, the nerve enters the gluteus maximus muscle, innervates it, and also gives branches to the capsule of the hip joint.

The pudendal nerve (n. pudendus) is formed by the anterior branches of the SIII-SIV, partially SII spinal roots. It is located below the sacral plexus on the anterior surface of the sacrum at the lower edge of the piriformis muscle. From this nerve, motor fibers extend to the levator ani muscle and the coccygeus muscle. The largest branch of the pudendal plexus is the nerve of the same name - n. Pudendus. This nerve exits the pelvic cavity under piriformis muscle, goes around the ischial tuberosity and passes through the lesser sciatic foramen to the lateral wall of the ischiorectal fossa. Here it is divided into branches:

inferior rectal nerves (pass to the muscle that compresses the anus and to the skin of the anterior part of the anus);
The perineal nerve passes to the superficial transverse perineal muscle, the bulbocavernosus muscle, and also to the skin of the posterior aspect of the scrotum or labia majora.

The dorsal nerve of the penis/clitoris - n. - also departs from the pudendal nerve. dorsalis penis (clitoridis). Its branches supply the deep transverse perineal muscle and the constrictor urethra, as well as the skin of the penis/clitoris and the urethra.

In the ischiorectal fossa, the pudendal nerve gives off the inferior rectal and perineal nerves. The lower rectal nerves (nn. rectales inferiores) penetrate the ischiorectal fossa and innervate the external anal sphincter and the skin of the anal area. Perineal nerves (nn. perineales) innervate the muscles and skin of the perineum of the scrotum in men and the labia majora in women. The final branch of the pudendal nerve is the dorsal nerve of the penis or clitoris (n. dorsalis penis, s. clitoridis). This nerve passes through the urogenital diaphragm next to the artery of the same name on the dorsum of the penis (clitoris), gives branches to the cavernous bodies, the head of the penis (clitoris), the skin of the penis in men, the labia majora and minora in women, as well as branches to deep transverse perineal muscle and urethral sphincter.

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

The posterior cutaneous nerve of the thigh (n. cutaneus femoris posterior) is formed by fibers of the anterior branches of the first to third sacral spinal nerves (SI-SIII). The nerve exits the pelvic cavity through the infrapiriform foramen and descends next to the sciatic nerve. Next, the posterior cutaneous nerve of the thigh goes down in the groove between the semitendinosus and biceps femoris muscles. Its branches pass through the fascia lata of the thigh, branching in the skin of the posteromedial surface of the thigh up to the popliteal fossa and the upper part of the leg. Near the lower edge of the gluteus maximus muscle, the lower nerves of the buttocks (nn. clunium inferiores) and perineal branches (rr. perineales) extend to the skin of the perineum from the posterior cutaneous nerve of the thigh. The inferior nerves of the buttocks innervate the skin of the lower part of the gluteal region.

The sciatic nerve (n. ischiadicus) is the largest nerve of the human body. It is formed by fibers of the anterior branches of the fourth and fifth lumbar (LIV-LV), first and second sacral (SI-II) spinal nerves. The nerve exits the pelvic cavity through the infrapiriform foramen along with the inferior gluteal and pudendal nerves, arteries of the same name and the posterior cutaneous nerve of the thigh. The sciatic nerve then runs approximately midway between the ischial tuberosity and the greater trochanter femur along the posterior surface of the twin muscles, obturator internus and quadratus femoris. Beneath the inferior border of the gluteus maximus muscle, the sciatic nerve passes along the posterior surface of the adductor magnus muscle and anterior to the long head of the biceps femoris muscle. At the level of the upper angle of the popliteal fossa, and sometimes higher, it is divided into the tibial and common peroneal nerves.

In the pelvis and thigh, the sciatic nerve gives off muscle branches to the obturator internus, gemellus, quadratus femoris, semitendinosus and semimembranosus muscles, the long head of the biceps femoris and the posterior part of the adductor magnus muscle.

The tibial nerve (n. tibialis) is much thicker than the common peroneal nerve. It descends vertically in the popliteal fossa, passes between the heads of the gastrocnemius muscle, posteriorly and slightly lateral to the popliteal artery and vein. Together with the posterior tibial artery, the nerve goes under the soleus muscle into the ankle-popliteal canal. In the lower leg, the tibial nerve is located between long muscle flexor big toe laterally and flexor digitorum longus medially. IN lower sections In the ankle-popliteal canal, the tibial nerve passes more superficially. In the groove at the posterior edge of the medial malleolus, the tibial nerve divides into its terminal branches, the medial and lateral plantar nerves.

The tibial nerve along its length gives numerous muscle branches to the triceps surae muscle, long flexor of the fingers and big toe, to the plantar and popliteal muscles. Sensitive branches The tibial nerve innervates the capsule of the knee joint, the interosseous membrane of the leg, the capsule of the ankle joint, and the bones of the leg. The largest sensory branch of the tibial nerve is the medial cutaneous nerve of the calf (n. cutaneus surae medialis). It arises from the tibial nerve at the level of the popliteal fossa, then, in the form of a long and thin branch, passes first under the fascia of the leg, between the heads of the gastrocnemius muscle. At the level of the origin of the distal gastrocnemius tendon, this nerve pierces the fascia and exits under the skin and connects with the lateral cutaneous nerve of the calf (from the common peroneal nerve). When these two nerves merge, the sural nerve (n. suralis) is formed, which passes first behind the lateral malleolus, then along the lateral edge of the foot called the lateral dorsal cutaneous nerve (n. cutaneus dorsalis lateralis). This nerve innervates the skin of areas adjacent to the nerve, and near the calcaneus it gives off cutaneous lateral calcaneal branches (rr. calcanei laterales).

The medial plantar nerve (n. plantaris medialis), which is one of the terminal branches of the tibial nerve, on the foot runs along the medial edge of the flexor digitorum brevis tendon in the medial plantar groove, next to the medial plantar artery. On the foot, the nerve gives off muscle branches to the short flexor of the fingers and big toe, to the abductor pollicis muscle, as well as to the two medial lumbrical muscles. At the level of the base of the metatarsal bones, the medial plantar nerve gives off the first proper plantar digital nerve (n. digitalis plantaris proprius) to the skin of the medial edge of the foot and big toe, as well as three common plantar digital nerves (nn. digitales plantares communes). These digital nerves pass under the plantar aponeurosis along with the plantar metatarsal arteries. Each common plantar digital nerve at the level of the metatarsophalangeal joints is divided into two own plantar digital nerves (nn. digitales plantares proprii), which innervate the skin of the I-IV fingers facing each other.

The lateral plantar nerve (n. plantaris lateralis) is thinner than the medial one. It is located in the lateral plantar groove between the quadratus plantaris muscle and the flexor digitorum brevis muscle. At the proximal portion of the fourth intermetatarsal space, the lateral plantar nerve divides into deep and superficial branches. The deep branch (r. profundus) gives branches to the quadratus plantae muscle, the abductor little finger muscle, the flexor little finger brevis muscle, the 3rd and 4th lumbrical muscles, and the interosseous muscles; to the adductor hallucis muscle and to the lateral portion of the flexor hallucis brevis muscle. The superficial branch (r. superficialis) of the lateral plantar nerve gives off cutaneous branches to the lateral side of the little finger and the sides of the IV and V fingers facing each other (common plantar digital nerve, n. digitalis plantaris communis), which divides into two proper plantar digital nerves (nn. digitales plantares propria).

The common peroneal nerve (n. fibularis communis) is the second major branch of the sciatic nerve, directed obliquely downward and laterally. The nerve occupies the lateral part of the popliteal fossa, giving branches to the knee and tibiofibular joints, to the short head of the biceps femoris muscle. At the level of the popliteal fossa, the lateral cutaneous nerve of the calf (n. cutaneus siirae lateralis) departs from the common peroneal nerve, which gives off cutaneous branches to the lateral side of the leg, and at the level of the middle of the back side of the leg it pierces the fascia, exits under the skin and connects with the medial cutaneous nerve of the calf (forms sural nerve).

The common peroneal nerve, near the lateral angle of the popliteal fossa, bends around the neck of the fibula on the lateral side. The nerve then pierces the initial part of the peroneus longus muscle and divides into the superficial and deep peroneal nerves.

The superficial peroneal nerve (n. fibularis superficialis, s. peroneus superficialis) runs down and laterally in the superior musculofibular canal, innervating the short and long peroneus muscles. At the border of the middle and lower thirds of the leg, the nerve leaves the superior musculofibular canal, pierces the fascia of the leg, goes down and medially towards the dorsum of the foot. In the superolateral region of the foot (or just above) it is divided into the medial and intermediate dorsal cutaneous nerves. The medial dorsal cutaneous nerve (n. cutaneus dorsalis medialis) innervates the skin of the dorsum of the foot near its medial edge and the skin of the dorsum of the II and III fingers facing each other. The intermediate dorsal cutaneous nerve (n. cutdneus dorsalis intermedius) innervates the skin of the superolateral surface of the dorsum, as well as the sides of the third, fourth and fifth fingers facing each other (dorsal digital nerves of the foot, nn. digitales dorsales pedis).

The deep peroneal nerve (n. fibularis profundus, s. peroneus profundus) from its origin goes in the medial direction, passes through the hole in the anterior intermuscular septum of the leg. Next, the nerve goes through the thickness of the long muscle that extends the fingers. Together with the anterior tibial artery and veins, the nerve descends along the anterior surface of the interosseous membrane of the leg. For some distance, the neurovascular bundle passes between the tibialis anterior muscle medially and the extensor digitorum longus muscle laterally. Next, the deep peroneal nerve goes down next to the tendon extensor longus big toe (foot). On the dorsum of the foot, the nerve passes under the short extensor of the big toe, then in the first intermetatarsal groove. At the level of the distal part of the first intermetatarsal space, the deep peroneal nerve is divided into two terminal branches - the dorsal digital nerves (nn. digitales dorsales), innervating the skin of the sides of the first and second toes facing each other.