Lumbar plexus

The lumbar plexus (plexus lumbalis) is formed by the anterior branches of the three upper lumbar (LI-LIII), part of the anterior branch of the twelfth thoracic (ThXII) and part of the fibers of the anterior branch of the fourth lumbar (LIV) spinal nerves. The remaining parts of the anterior branches of the fourth and fifth lumbar spinal nerves are joined under the name of the lumbar-sacral trunk, which descends into the pelvic cavity. The lumbar plexus in the form of interconnected anterior branches of the spinal nerves is located anterior to the transverse processes of the lumbar vertebrae and on the front surface of the square lumbar muscle, in the thick of the large lumbar muscle. The branches of the lumbar plexus appear from under the lateral edge of this muscle or perforate it and innervate some of the muscles and skin of the abdominal wall, the skin of the external genitalia, the skin and muscles of the medial side of the thigh, the skin of the medial surface of the shin. The branches of the lumbar plexus are the muscle branches, the ilio-hypogastric nerve, the ilio-inguinal, femoral-genital nerves, the lateral cutaneous nerve of the thigh, the blocking and femoral nerves.

Muscular branches (rr. Musculares) begin from all the anterior branches forming the lumbar plexus, even before they join each other. These branches are directed to the square muscle of the waist, small and large lumbar muscles, interdispersed lateral muscles of the waist.

Lumbar plexus, its branches and innervated organs

Nerves of the lumbar plexus	Segments of the spinal cord	Innervable organs
Muscular branches	Th XII- LI-LIV	Square lumbar muscle, large and small lumbar muscles, lateral interdigitic lumbar muscles
The iliac-hypogastric nerve	ThxII-LI	Transverse abdominal muscle, external and internal oblique abdominal muscles, pyramidal muscle. The skin of the upper-lateral part of the gluteal region, the upper-lateral region of the thigh, the skin of the pubic region
Ilio-inguinal nerve	ThxII-LI	Transverse abdominal muscle, external and internal oblique abdominal muscles. Skin pubic, inguinal area, penis, anterior side of the scrotum (large labia)
Femoral nerve	LI-LII	The muscle that lifts the testicle. The skin of the upper medial side of the thigh, the scrotum (large labia), the area of the subcutaneous ring of the femoral canal
Lateral cutaneous nerve of hip	LI-LII	The skin of the lateral side of the thigh (to the level of the knee joint)
Obstruction nerve	LII-LIV	A long, short and large leading muscles, a comb muscle, a thin muscle, an external obturator muscle. The skin of the medial side of the thigh, the knee joint capsule
Femoral nerve	LI-LIV	Tailoring, comb muscle; quadriceps femoris. The skin of the front side of the thigh, the anterior medial side of the tibia, the rear and the medial edge of the foot (up to the thumb)

The iliac hypogastric nerve (n. Ilioliypogastricus, THXII-LI) perforates the lateral part of the large lumbar muscle, passes behind the kidney (along the front surface of the square muscle of the waist). Next, the nerve goes forward and down and, not reaching the iliac crest, perforates the transverse abdominal muscle, where it lies between this muscle and the internal oblique muscle of the abdomen, giving them the muscle branches. Further, the ilio-celiac nerve, at the level of the middle iliac crest, gives the lateral cutaneous branch (r. Cutaneus lateralis), which perforates the muscles of the abdominal wall and branches into the skin of the lateral region of the thigh above the large trochanter. The anterior cutaneous branch (r. Cutaneus anterior) passes through the aponeurosis of the external oblique abdominal muscle, innervates the skin next to the outer ring of the inguinal canal. The terminal branch of the ilio-hypogastric nerve branches into the skin of the lower abdomen over the pubic symphysis.

The ilio-inguinal nerve (n. Ilionguinalis) is formed by the fibers of the twelfth thoracic and anterior branch of the first lumbar spinal nerves (ThXII-LI). The nerve emerges from under the lateral margin of the large lumbar muscle and extends below the ilio-hypogastric nerve along the anterior surface of the square muscle of the waist, almost parallel to the crest of the ilium. In the initial section, the nerve is covered by the transverse fascia of the abdomen, then goes between the transverse and internal oblique muscles of the abdomen, innervates them. Further passes into the inguinal canal, appears through its outer ring and branches into the skin of the pubis, scrotum in men (anterior scrotal nerves, n. Scrotales anteriores) or large labia in women (anterior labial nerves, nn. Labiales anteriores).

The femoral-genital nerve (n. Genitofemoralis) is formed by the fibers of the anterior branches of the first and second lumbar spinal nerves (LI-LII). The nerve passes through the thickness of the large lumbar muscle on its front surface, where it soon divides into two branches - the sex and femoral. The sexual branch (r. Genitalis), or the external seminal nerve, runs down the anterior surface of the large lumbar muscle laterally and anterior to the external iliac artery, perforating the posterior wall of the inguinal canal slightly medial to the deep ring. Together with the spermatic cord, the sexual branch goes in the inguinal canal, innervates the muscle that lifts the testicle, and the skin of the scrotum, the fleshy membrane and the skin of the upper median region of the thigh. In women, this branch goes along with the round ligament of the uterus in the inguinal canal and ends near its superficial ring and in the skin of the large labia. The femoral branch (r. Fioralis) is directed down the anterior surface of the large lumbar muscle. Then this branch passes lateral to the external iliac artery under the inguinal ligament and branches into the skin of the thigh just below this ligament.

The lateral cutaneous nerve of the thigh (n. Cutaneus fioris lateralis) is formed by the fibers of the anterior branches of the first and second lumbar spinal nerves (LI-LII). The nerve emerges from under the lateral edge of the large lumbar muscle (or from the muscle mass). Next, the nerve goes along the anterior surface of the iliac muscle (under its fascia), reaches the anterior superior iliac spine. Lateral to the beginning of the sartorius muscle, the nerve passes under the inguinal ligament on the thigh. On the thigh, the nerve goes down first under the broad fascia of the thigh, then divides into branches that perforate this fascia and branch out into the skin of the lateral side of the thigh to the knee joint.

The obturatorial nerve (n. Obturatorius) is formed by the fibers of the foreground of the second to fourth lumbar spinal nerves (LII-LIV). The nerve emerges from under the medial edge of the large lumbar muscle, below the border line lies on the lateral surface of the small pelvis. Together with the same artery and vein, the nerve passes through the occlusion channel to the medial side of the thigh. Before entering the canal, the nerve gives the branch to the external occlusive muscle. In the locking channel or immediately after the exit from it, the nerve is divided into the anterior and posterior branches. The anterior branch (r. Anterior) gives the muscle branches to the long and short adductor muscles, to the thin muscle and the cutaneous branch that goes between the thin and long adductor muscles to the skin of the medial thigh surface. The posterior branch (r. Posterior) of the occlusal nerve passes through the outer obturator and also delivers branches to the capsule of the hip joint, the crural muscle and the posterior side of the capsule of the knee joint.

The femoral nerve (n. Femoralis), the largest, thick nerve of the lumbar plexus, consists of the fibers of the anterior branches of the second to fourth lumbar spinal nerves (LII-LIV), which combine into the nerve in the thick of the large lumbar and ileum muscles. From the pelvic cavity to the thigh, the nerve leaves through the muscle lacuna. In the femoral triangle, the nerve is located lateral to the femoral vessels, being covered with a deep leaf of the wide fascia of the thigh. At 3-4 cm below the inguinal ligament, the femoral nerve is divided at once or gradually into the muscle, skin branches and subcutaneous nerve. Muscular branches go to the iliac muscle, the quadriceps muscle of the thigh, tailor and comb muscle, to the capsule of the hip joint.

The number and position of cutaneous branches are variable. These branches innervate the skin of the anterior surface of the thigh to the level of the patella.

The subcutaneous nerve (n. Saphenus) is the longest cutaneous branch of the femoral nerve. It is located in one fascial vagina with the femoral artery and vein. At first, the nerve lies lateral to the artery, then passes to its anterior surface. Together with the femoral artery, the nerve enters the leading canal, and it leaves the canal through an opening in its anterior wall (along with the descending artery of the knee).

At the level of the knee joint, or just below it from the subcutaneous nerve, the podadnikonnikovaya branch (r. Infrapatellaris) and the medial cutaneous branches of the lower leg (rr. Cutanei cruris mediales) depart. Giving the subordinate branch, the subcutaneous nerve perforates the fascia of the shank at the level of tuberosity of the tibia, descends along the medial surface of the shin next to the large saphenous vein of the foot, lateral to it, innervating the skin of the anterior medial aspect of the tibia. Below the subcutaneous nerve passes slightly in front of the medial malleolus, goes to the medial side of the foot to the thumb.

[1], [2], [3], [4], [5]