Sacral plexus

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

Short branches. Short inner branches of the sacral plexus include the internal blocking nerve (from LIV-SII), the pear-shaped nerve (from SI-SII), the nerve of the square muscle of the thigh (from LIV-SII, reaching the same muscles, and the upper and lower gluteal and sexual nerves.

The superior gluteus nerve (n. Gluteus superior) is formed by the fibers of the anterior branches of the fourth and fifth lumbar (LIV-LV) and the first sacral (SI) spinal nerves. Together with the artery of the same name, the nerve leaves the pelvic cavity through the supragene-like opening. The upper branch of this nerve goes forward to the small buttock muscle and innervates it. The lower branch of the upper gluteal nerve passes between the small and middle gluteus muscles, innervates them, and also gives the branch to the muscle, which strains the wide fascia of the thigh.

The lower gluteus nerve (n. Gluteus inferior) consists of the fibers of the anterior branches of the fifth lumbar (LV) and first-second sacral (SI-SII) spinal nerves. From the cavity of the small pelvis, the nerve exits through the sub-arched aperture along with the artery of the same name. Fan-like divergent short branches nerve enters the gluteus maximus, innervates it, and also gives branches to the capsule of the hip joint.

The genital nerve (n. Pudendus) is formed by the anterior branches of SIII-SIV, partially the SII spinal roots. It is located below the sacral plexus on the anterior surface of the sacrum at the lower edge of the pear-shaped muscle. From this nerve, the motor fibers move to the muscle that raises the anus and to the coccygeal muscle. The largest branch of the plexus plexus is the eponymous nerve - n. Pudendus. This nerve leaves the pelvic cavity under the pear-shaped muscle, rounds the sciatic tubercle and passes through the small sciatic hole to the lateral wall of the sciatic-rectum fossa. Here it is divided into branches:

1. lower rectal nerves (pass to the muscle, compressing the anus, and to the skin of the anterior part of the anus);
2. the perineal nerve passes to the superficial transverse muscle of the perineum, the bulbous cavernous muscle, and also to the skin of the back of the scrotum or large labia.

The posterior nerve of the penis / clitoris also departs from the genital nerve - n. Dorsalis penis (clitoridis). Its branches supply the deep transverse muscle of the perineum and compresses the original part of the urethra, as well as the skin of the penis / clitoris and the urethra.

In the sciatic and rectum fossa the sexual nerve gives the lower rectal and perineal nerves. The lower rectum nerves (nn rectales inferiores) penetrate the sciatic-rectum fossa, innervate the external sphincter of the anus and the skin of the anal region. The perineal nerves (nn. Perineales) innervate the muscles and skin of the perineum of the scrotum in men and the large labia in women. The final branch of the genital 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 same artery on the back surface of the penis (clitoris), gives branches to the cavernous bodies, the head of the penis (clitoris), the skin of the penis in men, the large and small labia in women, and the branches to deep transverse muscle perineum and sphincter of the urethra.

Long branches of the sacral plexus. To the long branches of the sacral plexus belong the posterior cutaneous nerve of the thigh and sciatic nerve.

The posterior cutaneous nerve of the thigh (n. Cutaneus femoris posterior) is formed by the fibers of the anterior branches of the first-third sacral spinal nerves (SI-SIII). The nerve leaves the cavity of the small pelvis through the podrushevidnoe opening and descends down next to the sciatic nerve. Further, the posterior cutaneous nerve of the femur goes downward in the furrow between the semitendinous and biceps femoris muscles. Its branches pass through the broad fascia of the thigh, branch into the skin of the median posterior medial thigh until the popliteal fossa and upper leg. Near the lower edge of the gluteus maximus, the lower nerves of the buttocks (nn., Clunium inferiores) and the perineal branches (r. Perineales) from the posterior cutaneous nerve of the femur extend to the perineal skin. The lower nerves of the buttocks innervate the skin of the lower part of the gluteal region.

The sciatic nerve (n. Ischiadicus) is the largest nerve in the human body. It is formed by the fibers of the anterior branches of the fourth and fifth lumbar (LIV-LV), the first and second sacral (SI-II) spinal nerves. The nerve leaves the pelvic cavity through the podrushevidnoe aperture together with the lower gluteal and sexual nerves, the same arteries and the posterior cutaneous nerve of the thigh. The sciatic nerve further extends approximately in the middle between the ischial tuber and the large trochanter of the femur along the back surface of the twin muscles, the inner blocking and square muscles of the thigh. Under the lower edge of the gluteus maximus, the sciatic nerve passes along the posterior surface of the large adductor muscle and anterior to the long head of the biceps femoris muscle. At the level of the upper corner of the popliteal fossa, and sometimes higher it is divided into the tibial and common peroneal nerves.

In the pelvic region and on the thigh from the sciatic nerve, the muscle branches extend to the inner locking, twin muscles, to the square muscle of the thigh, the semitendinosus and the semimembranous muscle, to the long head of the biceps femoris and the back of the large adductor muscle.

The tibial nerve (n. Tibialis) is much thicker than the common peroneal nerve. It descends vertically in the popliteal fossa, passes between the calf muscles, posterior and slightly lateral to the popliteal artery and vein. Together with the posterior tibial artery, the nerve is guided under the soleus muscle into the knee-popliteal canal. On the shin the tibial nerve is located between the long muscle flexing the big toe, laterally and the long muscle flexing the fingers, medially. In the lower parts of the knee-popliteal channel, the tibial nerve passes more superficially. In the furrow on the posterior edge of the medial malleolus, the tibial nerve is divided into its terminal branches - the medial and lateral plantar nerves.

The tibial nerve along its length gives numerous muscle branches to the triceps muscles of the lower leg, the long flexors of the fingers and the thumb of the foot, to the plantar and popliteal muscles. Sensitive branches of the tibial nerve innervate the capsule of the knee joint, the intercostal membrane of the lower leg, the capsule of the ankle joint, the shin bone. The largest sensory branch of the tibial nerve is the medial cutaneous nerve of the calf (n. Cutaneus surae medialis). It departs 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 shank, between the calf muscles. At the level of the beginning of the distal tendon of the gastrocnemius muscle, this nerve perforates the fascia and goes under the skin and connects to the lateral cutaneous nerve of the calf (from the common peroneal nerve). When these two nerves merge, the calf nerve (n. Suralis) is formed, which first passes behind the lateral ankle, then along the lateral edge of the foot called the lateral dermal cutaneous nerve (n. Cutaneus dorsalis lateralis). This nerve innervates the skin adjacent to the nerve areas, and near the calcaneus gives the skin lateral calcaneal branches (r. Calcanei laterales).

The medial plantar nerve (n. Plantaris medialis), which is one of the terminal branches of the tibial nerve, on the foot goes along the medial edge of the tendon of the short flexor of the fingers in the medial plantar sulcus, next to the medial plantar artery. On the foot, the nerve gives the muscle branches to the short flexors of the fingers and thumb of the foot, to the muscle that removes the thumb, and also to the two medial vermicular muscles. At the level of the base of the metatarsal bones, the medial plantar nerve gives the first native plantar digital nerve (n. Digitalis plantaris proprius) to the skin of the medial edge of the foot and thumb, as well as three common plantar nerve (nn. Digitales plantares communes). These digital nerves pass under the plantar aponeurosis together with the plantar metatarsus arteries. Each joint plantar nerve at the level of metatarsophalangeal joints is divided into two of its own plantar digital nerves (nn. Digitales plantares proprii), which innervate the skin of the first to fourth fingers facing each other.

The lateral plantar nerve (n. Plantaris lateralis) is thinner than the medial nerve. It is located in the lateral plantar groove between the square muscle of the sole and the short flexor of the fingers. In the proximal part of the fourth interlacing interval, the lateral plantar nerve is divided into deep and superficial branches. The deep branch (r. Profundus) gives branches to the square muscle of the sole, the muscle that removes the little finger, to the short flexor of the little finger, to the 3rd and 4th worm-like muscles, to the interosseous muscles; to the muscle that leads the thumb of the foot, and to the lateral part of the short flexor of the big toe. The superficial branch (r. Superficialis) of the lateral plantar nerve gives the cutaneous branches to the lateral side of the little finger and the sides of the fourth and fifth fingers (the common plantar nerve, n. Digitalis plantaris communis) facing each other and dividing into two of its own plantar digital nerves (nn. Digitales plantares proprii).

The common peroneus nerve (n. Fibularis [peroneus] 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 spine, to the short head of the biceps femoris. At the level of the popliteal fossa from the common peroneal nerve, the lateral cutaneous nerve of the calf (n. Cutaneus siirae lateralis) that extends the cutaneous branches to the lateral side of the shank, and at the middle of the posterior side of the tibia perforates the fascia, goes under the skin and connects to the medial cutaneous nerve of the calf (forms the calf nerve).

The common peroneal nerve near the lateral corner of the popliteal fossa curves around the lateral side of the fibula. Then the nerve will perforate the initial part of the long fibular muscle and divide into the superficial and deep peroneal nerves.

The superficial peroneal nerve (n. Fibularis superficialis, S. Peroneus superficialis) goes downward and laterally in the upper muscular-peroneal canal, innervates the short and long fibular muscles. On the border of the middle and lower thighs, the nerve emerges from the upper muscular-peroneal canal, perforates the fascia's fascia, goes downward and medially towards the rear of the foot. In the upper-lateral region of the foot (or slightly higher) it divides into the medial and intermediate dorsal cutaneous nerves. The medial dorsal cutaneous nerve (n. Cutaneus dorsalis medialis) innervates the skin of the rear of the foot near its medial edge and the skin of the rear of the II and III fingers facing each other. The intermediate dorsal cutaneous nerve (n. Cutdneus dorsalis intermedius) innervates the skin of the superior lateral surface of the rear, as well as the faces of the III, IV and V fingers (back nerves of the foot, nn. Digitales dorsales pedis) facing each other.

The deep peroneal nerve (n. Fibularis profundus, S. Peroneus profundus) from the place of origin goes in the medial direction, passes through the hole in the anterior intermuscular septum of the shin. Next, the nerve goes in the thickness of the long muscle, extending the fingers. Together with the anterior tibial artery and veins, the nerve descends along the anterior surface of the interosseous membrane of the tibia. At some distance, the neurovascular bundle passes between the anterior tibial muscle medially and the long muscle, extending the fingers, laterally. Further, the deep peroneal nerve goes down next to the tendon of the long extensor of the big toe (foot). At the rear of the foot, the nerve passes under the short extensor of the thumb of the foot, then in the first intercostal sulcus. At the level of the distal part of the first intercellular gap, the deep peroneal nerve is divided into two terminal branches - the back digital nerves (nn. Digitales dorsales), innervating the skin of the first and second toes of the foot facing each other.

On the shin the deep peroneal nerve gives branches to the anterior tibial muscle, the long extensor of the toes (feet), and also to the long extensor of the big toe. At the rear of the foot, the deep peroneal nerve innervates the short extensor of the fingers and the short extensor of the big toe. Delivers sensitive branches to the ankle joint, to the joints and bones of the foot.

[1], [2], [3], [4]