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1.    Arteries of lower limb. Femoral and popliteal arteries. Arteries of the leg  Arteries of the foot. Veins, lymphatic vessels and nodes of lower limb

2.     Lumbar spinal nerves. Lumbar, Sacral and coccygeal spinal nerves. Sacral and coccygeal plexus

    3.    Preparation of vessels and nerves of extremities.

 

Lesson # 30

Theme 1. Arteries of lower limb. Femoral and popliteal arteries.

Femoral artery is continuation of external iliac artery, which passes under inguinal ligament through lacuna vasorum laterally from femoral vein. Then femoral artery runs downward in iliopectineal sulcus and anterior femoral sulcus. It enters into adductorial canal and exits from canal in popliteal fossa where contines into popliteal artery.

Obliterative vascular disease of the lower extremities (disease involving the narrowing of vessel lumen) took first place in the clinical value and the frequency and constitute a major group of organic arteriopatiy available surgical treatment. For the diagnosis and treatment of these conditions is necessary to know, first normal vascular anatomy, their branching and topographic relationship.

Vascular obliteration leg and feet is a sign of obliterating endarteriitu, mainly affects men aged 20-40 years and can cause limb amputation and disability at a young age. Deep knowledge of anatomy vessels allow future vascular surgeons more accurate diagnosis of this disease and to carry out various preventive measures aimed at preventing the development of vascular disease.

Femoral artery (a. femoralis) is a direct continuation of the external iliac artery (a.iliaca externa), passes under the inguinal ligament (lig.inguinale) through a vascular Bay (lacuna vasorum), accompanied by a lateral vein of the same name appears on the front section hip side of the femoral vein (v.femoralis).

 

 

Next femoral artery (a. femoralis) lies in the iliac combed groove (sulcus iliopectineus), runs down the anterior femoral region (regio femoris anterior) in the femoral sulcus (sulcus femoralis) and enters the adductor canal (canalis adductorius), through which penetrates in the popliteal fossa (fossa poplitea),  which continues in the popliteal artery (a. poplitea).

Femoral artery projected onto the front surface of the skin along the hips straight line connecting a point on the boundary between the middle and inner thirds lig. inguinale of the medial epicondyle of the femur.

Closer to the surface, it is the inguinal ligament, where pressing the vessel to the upper branch of the pubic bone, it is easily detectable pulse.

Femoral artery gives off:

·          superficial epigastric artery passes on anterior abdominal wall and supplies a inferior portion of external oblique muscle aponeurosis and skin;

·          superficial circumflexа iliac artery passes laterally and ramifies in muscles and skin near superior anterior iliac spina;

·          deep femoral artery gives off medial circumflex femoral artery and lateral circumflexа artery, three perforating arteries, that supply posterior group of thigh muscles; away from the posterior femoral artery semicircle 3 - 4 cm below the inguinal ligaments, goes deeper and down, accompanied by the same name veins, forming branches: prpserednyu artery that goes around the thigh (a. circumflexa femoris medialis), which carries blood to the actuating m 'thigh muscles and hip joint, lateral artery that goes around the thigh (a. circumflexa femoris lateralis), which powers the quadriceps and sartorius thigh muscle - natyahach broad fascia and middle gluteal muscle, femur, hip joint capsule and appropriate skin; pronyzni artery (aa. perforates) - three very large branches that supply blood to most of the muscles of the back of the thigh and femur.

·          descending genu artery begins from femoral artery in adductorial canal, passes through the tendinous hiatus of this canal and passes down together with saphenus nerve to knee-joint, where takes hand in formation of articulate knee net (rete articulare genus). departs from the femoral artery (a. femoralis) in the drive channel (canalis adductorius), goes to the front surface of the thigh (facies anterior femoris) through the drive roztvir (hiatus adductorius) of this channel and falls to the knee joint (art. genus), which is involved in the formation of articular knee mesh (rete articulare genus), so supplies blood vastus medialis and articulatio genus.

Distal branches of the deep artery of the thigh combined well with each other and with the branches of the popliteal artery, which is very important for the development of bypass blood flow in the femoral artery ligation event following discharge deep artery of the thigh.

Numerous muscular branches of the middle region of small caliber away from the femoral artery to the surrounding muscles.

The femoral artery.

 

Popliteal artery is continuation of femoral artery, passes in advance of tibial nerve and popliteal vein and on level of inferior margin of popliteal muscle divides into anterior tibial artery and posterior tibial artery.

Popliteal artery gives off the following branches:

·          superior medial and lateral genu arteries;

·          middle genu artery;

·          inferior medial and lateral genu arteries.

All these arteries participate in feeding of knee-joint and muscles around it.

Circumpatellar anastomosis.

 

 

These arteries are involved in the blood supply of the knee joint (art. genus) and muscles (musculi) around it.

They are involved in the formation of:

- Articular knee mesh (rete articulare genus);

- Patellar rete (rete patellare).

 

All these branches with descending artery knees (from the femoral artery) and the anterior tibial artery branches form around the knee thick knee joints net (rete articulare genus), which supplies blood, soft tissues, bones, muscles and intraarticular knee lesions joint.

Popliteal artery (a. poplitea) down from top to bottom, situated deep in the popliteal fossa, where the accompanying vein of the same name (passing over the surface) and the tibial nerve, which lies directly beneath the fascia. Next artery divides into anterior and posterior tibial arteries.

 

 

THEME  2.   Arteries of the leg

Posterior tibial artery continues from popliteal artery, passes in cruropopliteal canal, under musculus soleus, behind medial malleolus, passes in separate fibrous canal under flexors tendom retinaculum on sole, where subdivides into medial plantar artery and lateral plantar artery.

 

The popliteal, posterior tibial, and peroneal arteries.

Branches of posterior tibial artery:

·          fibular artery;

·          medial malleolar branches;

·          muscular branches;

·          fibular circumflexа branch;

·          lateral plantar artery;

·          medial plantar artery.

 

Lateral plantar artery (a. plantaris lateralis) gives four soles metatarsus artery (aa. metatarsales plantares), which pass into common Soles finger artery (aa. digitales plantares communes).

Each of these arteries (aa. digitales plantares communes) splits into two soles of their finger artery (aa. digitales plantares propriae), which krovopostachayut on the sole (planta) skin on both sides of the respective toes (cutis digitorum pedis).

7. Medial plantar artery (a. plantaris medialis), which is one of the final branches of the posterior tibial artery (a. tibialis posterior), has a deep branch (ramus profundus) and the superficial branch (ramus superficialis), lies in the medial plantar sulcus (sulcus plantaris medialis ) and krovopostachaye medial foot muscles (musculi mediales plantae), anastomosing on the back of the first metatarsal artery (a. metatarsalis dorsalis prima).

8. Anterior tibial artery (a. tibialis anterior), which departs from the popliteal artery (a. poplitea) in the popliteal fossa (fossa poplitea), comes in ankle-popliteal canal (canalis cruropopliteus) and immediately comes out of it through the upper section of the interosseous membrane (membrana interossea).

 

 

Anterior tibial artery begins from popliteal artery in popliteal fossa, runs at cruropopliteal canal and makes perforating in superior portion of interossea membrane. Artery lies on anterior surface of interossea membrane between muscles of anterior shin group and, passing under retinaculum of extensor muscles, continues on foot under name of dorsal pedis artery.

Anterior tibial artery gives off the following branches:

·          posterior recurrent tibial artery takes hand in formation of articulate knee net;

·          anterior recurrent tibial artery takes hand in formation of articulate knee net;

·          muscular branches supply anterior shin muscles group;

·          anterior medial maleolar artery takes hand in formation medial maleolar net;

Anterior tibial artery (a. tibialis anterior) through the front hole ankle, hamstring channel enters the anterior lower leg area, which descends between t tibialis anterior and extensor digitorum so the front surface of the interosseous membrane (facies anterior membranae interosseae) between the anterior of tibia (musculi compartimenti cruris anterioris) and passing under the upper holder extensor muscles (retinaculum musculorum extensorum superius) and under the lower holder extensor muscles (retinaculum musculorum extensorum inferius), continues on foot called back foot arteries (a. dorsalis pedis). Two veins accompany the artery and deep peroneal nerve.

From the anterior tibial artery (a. tibialis anterior) depart the following branches:

- Rear swivel tibial artery (a. recurrens tibialis posterior), which participates in the knee joint net (rete articulare genus);

These vessels, rising up, taking part in the formation of the knee joint grid;

- Front swivel tibial artery (a. recurrens tibialis anterior), which participates in the formation of the knee joint net (rete articulare genus);

- Muscular branches (rr. musculares), which krovopostachayut muscles (musculi) anterior tibia (compartimentum cruris anterius), shin bone and skin;

- Front side stones artery (a. malleolaris anterior lateralis), which participates in the formation of lateral stone grids (rete malleolare laterale);

- Anterior medial stones artery (a. malleolaris anterior medialis), which participates in the formation of medial stone net (rete malleolare mediale).

Anterior tibial and dorsalis pedis arteries.

 

THEME  3.   Arteries of the  foot

·          fibular artery passes in inferior musculоfibular channel, supplies peroneal muscles and behind lateral malleolus divides into lateral maleolar branches and calcaneal branches;

·          medial malleolar branches take hand in formation of medial maleolar rete;

·          muscular branches supply deep and superficial muscles of posterior group in shin;

·          fibular circumflexа branch runs laterally from beginning of tibial artery and rounding a head of fibula joins to articulate knee net;

·          lateral plantar artery is a terminal branch of posterior tibial artery, lies in lateral plantar sulcus, passes medially and, anastomosing with deep plantar branch (from dorsal pedis artery), forms plantar arc. Lateral plantar artery gives off four plantar metatarsal arteries, which continue into common plantar digital arteries. Last subdivide into two proper plantar digital arteries, which supply skin of both sides of each finger on sole;

·          medial plantar artery is second terminal branches of posterior tibial artery (has a deep branch and superficial branch), lies into medial plantar sulcus and supplies muscles of medial plantar group, anastomosing with first dorsal metatarsal artery.

 

 

                                               

The plantar arteries.

   

         

Dorsal pedis artery - continuation of anterior tibial artery, directs to first interossea space of metatarsus, where subdivides into first dorsal metatarsal artery and deep plantar artery. First dorsal metatarsal artery subdivides into three dorsal digital arteries, which pass on both sides of dorsal surface of halux and medial side of second finger. Deep plantar branch passes through first intermetatarsal space on sole and, anastomosing with plantar arc. Dorsal pedis artery gives off also the lateral tarsal artery and medial tarsal artery to lateral and pedis margins medial and arcuate artery, from which the dorsal metatarsal arteries І-ІV start. Each from these arteries subdivides into two dorsal digital arteries, which supply dorsal surfaces of neighbouring fingers.

 

 

Veins, lymphatic vessels and nodes of lower limb

External iliac vein is continuation of femoral vein and receives blood from all veins of lower limb. Inferior epigastric vein and deep circumflexа ilei vein empties into external iliac vein under inguinal ligament.

The veins of lower limb subdivide into superficial and deep. Deep veins are double and accompany same name artery (only a popliteal vein and femoral vein are odd).

Follow veins belong to superficial veins of lower limb:

1.     Vena saphena magna has numerous valves, starts in front of medial malleolus, where receives influxes from plantar surface of foot, passes along saphenus nerve on medial leg surface upward, than on medial surface on thigh to saphaenus hiatus, where transfixes cribriform fascia and empties into femoral vein. Vena saphena magna has the numerous subcutaneous tributaries from anteromedial surface of leg, thigh and external genitals.

2.     Vena saphena parva has the numerous valves and collects blood from dorsal venous arch of foot, passes behind lateral malleolus, lies into sulcus between lateral and medial heads of gastrocnemius muscle and in popliteal fossa empties into popliteal vein.

The great saphenous vein and its tributaries at the fossa ovalis.

 

Follow vessels belong to deep veins of lower limb:

·          femoral vein;

·          deep femoral vein;

·          popliteal vein;

·          anterior tibial veins;

·          posterior tibial veins;

·          fibular veins.

  The Superficial Veins of the Lower Extremity

The superficial veins of the lower extremity are the great and small saphenous veins and their tributaries.

  On the dorsum of the foot the dorsal digital veins receive, in the clefts between the toes, the intercapitular veins from the plantar cutaneous venous arch and join to form short common digital veins which unite across the distal ends of the metatarsal bones in a dorsal venous arch. Proximal to this arch is an irregular venous net-work which receives tributaries from the deep veins and is joined at the sides of the foot by a medial and a lateral marginal vein, formed mainly by the union of branches from the superficial parts of the sole of the foot.

  On the sole of the foot the superficial veins form a plantar cutaneous venous arch which extends across the roots of the toes and opens at the sides of the foot into the medial and lateral marginal veins. Proximal to this arch is a plantar cutaneous venous net-work which is especially dense in the fat beneath the heel; this net-work communicates with the cutaneous venous arch and with the deep veins, but is chiefly drained into the medial and lateral marginal veins.

  The great saphenous vein (v. saphena magna; internal or long saphenous vein), the longest vein in the body, begins in the medial marginal vein of the dorsum of the foot and ends in the femoral vein about 3 cm. below the inguinal ligament. It ascends in front of the tibial malleolus and along the medial side of the leg in relation with the saphenous nerve. It runs upward behind the medial condyles of the tibia and femur and along the medial side of the thigh and, passing through the fossa ovalis, ends in the femoral vein.

 

Tributaries.—At the ankle it receives branches from the sole of the foot through the medial marginal vein; in the leg it anastomoses freely with the small saphenous vein, communicates with the anterior and posterior tibial veins and receives many cutaneous veins; in the thigh it communicates with the femoral vein and receives numerous tributaries; those from the medial and posterior parts of the thigh frequently unite to form a large accessory saphenous vein which joins the main vein at a variable level. Near the fossa ovalis  it is joined by the superficial epigastric, superficial iliac circumflex, and superficial external pudendal veins. A vein, named the thoracoepigastric, runs along the lateral aspect of the trunk between the superficial epigastric vein below and the lateral thoracic vein above and establishes an important communication between the femoral and axillary veins.

 

  The valves in the great saphenous vein vary from ten to twenty in number; they are more numerous in the leg than in the thigh.

  The small saphenous vein (v. saphena parva; external or short saphenous vein) begins behind the lateral malleolus as a continuation of the lateral marginal vein; it first ascends along the lateral margin of the tendocalcaneus, and then crosses it to reach the middle of the back of the leg. Running directly upward, it perforates the deep fascia in the lower part of the popliteal fossa, and ends in the popliteal vein, between the heads of the Gastrocnemius. It communicates with the deep veins on the dorsum of the foot, and receives numerous large tributaries from the back of the leg. Before it pierces the deep fascia, it gives off a branch which runs upward and forward to join the great saphenous vein. The small saphenous vein possesses from nine to twelve valves, one of which is always found near its termination in the popliteal vein. In the lower third of the leg the small saphenous vein is in close relation with the sural nerve, in the upper two-thirds with the medial sural cutaneous nerve.

 

The Deep Veins of the Lower Extremity

  The deep veins of the lower extremity accompany the arteries and their branches; they possess numerous valves.

The great saphenous vein and its tributaries.

 

The small saphenous vein.

 

  The plantar digital veins (vv. digitales plantares) arise from plexuses on the plantar surfaces of the digits, and, after sending intercapitular veins to join the dorsal digital veins, unite to form four metatarsal veins; these run backward in the metatarsal spaces, communicate, by means of perforating veins, with the veins on the dorsum of the foot, and unite to form the deep plantar venous arch which lies alongside the plantar arterial arch. From the deep plantar venous arch the medial and lateral plantar veins run backward close to the corresponding arteries and, after communicating with the great and small saphenous veins, unite behind the medial malleolus to form the posterior tibial veins.

  The posterior tibial veins (vv. tibiales posteriores) accompany the posterior tibial artery, and are joined by the peroneal veins.

  The anterior tibial veins (vv. tibiales anteriores) are the upward continuation of the venæ comitantes of the dorsalis pedis artery. They leave the front of the leg by passing between the tibia and fibula, over the interosseous membrane, and unite with the posterior tibial, to form the popliteal vein.

  The Popliteal Vein (v. poplitea) is formed by the junction of the anterior and posterior tibial veins at the lower border of the Popliteus; it ascends through the popliteal fossa to the aperture in the Adductor magnus, where it becomes the femoral vein. In the lower part of its course it is placed medial to the artery; between the heads of the Gastrocnemius it is superficial to that vessel; but above the knee-joint, it is close to its lateral side. It receives tributaries corresponding to the branches of the popliteal artery, and it also receives the small saphenous vein. The valves in the popliteal vein are usually four in number.

  The femoral vein (v. femoralis) accompanies the femoral artery through the upper two-thirds of the thigh. In the lower part of its course it lies lateral to the artery; higher up, it is behind it; and at the inguinal ligament, it lies on its medial side, and on the same plane. It receives numerous muscular tributaries, and about 4 cm. below the inguinal ligament is joined by the v. profunda femoris; near its termination it is joined by the great saphenous vein. The valves in the femoral vein are three in number.

  The Deep Femoral Vein (v. profunda femoris) receives tributaries corresponding to the perforating branches of the profunda artery, and through these establishes communications with the popliteal vein below and the inferior gluteal vein above. It also receives the medial and lateral femoral circumflex veins.

 

 

The popliteal vein.

 The Veins of the Abdomen and Pelvis

  The external iliac vein (v. iliaca externa), the upward continuation of the femoral vein, begins behind the inguinal ligament, and, passing upward along the brim of the lesser pelvis, ends opposite the sacroiliac articulation, by uniting with the hypogastric vein to form the common iliac vein. On the right side, it lies at first medial to the artery: but, as it passes upward, gradually inclines behind it. On the left side, it lies altogether on the medial side of the artery. It frequently contains one, sometimes two, valves.

 

Tributaries.—The external iliac vein receives the inferior epigastric, deep iliac circumflex, and pubic veins.

  The Inferior Epigastric Vein (v. epigastrica inferior; deep epigastric vein) is formed by the union of the venæ comitantes of the inferior epigastric artery, which communicate above with the superior epigastric vein; it joins the external iliac about 1.25 cm. above the inguinal ligament.

  The Deep Iliac Circumflex Vein (v. circumflexa ilium profunda) is formed by the union of the venæ comitantes of the deep iliac circumflex artery, and joins the external iliac vein about 2 cm. above the inguinal ligament.

  The Pubic Vein communicates with the obturator vein in the obturator foramen, and ascends on the back of the pubis to the external iliac vein.

  The hypogastric vein (v. hypogastrica; internal iliac vein) begins near the upper part of the greater sciatic foramen, passes upward behind and slightly medial to the hypogastric artery and, at the brim of the pelvis, joins with the external iliac to form the common iliac vein.

The femoral vein and its tributaries.

 

 

Tributaries.—With the exception of the fetal umbilical vein which passes upward and backward from the umbilicus to the liver, and the iliolumbar vein which usually joins the common iliac vein, the tributaries of the hypogastric vein correspond with the branches of the hypogastric artery. It receives (a) the gluteal, internal pudendal, and obturator veins, which have their origins outside the pelvis; (b) the lateral sacral veins, which lie in front of the sacrum; and (c) the middle hemorrhoidal, vesical, uterine, and vaginal veins, which originate in venous plexuses connected with the pelvic viscera.

 

The Lymphatics of the Lower Extremity

The superficial and deep vessels are distinguished in lower limb. The superficial vessels are situated over superficial fascia and deep vessels positioned closely to deep blood vessels. Popliteal nodes and inguinal nodes are distinguished in lower limb. Last one subdivide into deep inguinal nodes and superficial inguinal nodes. Superficial inguinal nodes dispose along inguinal ligament and lie on superficial sheet of fascia lata femoris. Their efferent vessels pass to external iliac nodes, which accompany same name artery.

The superficial vessels of lower limb formed from capillary skin networks and subcutaneous cellular tissue and form medial, lateral and posterior vessel groups.

Medial group of superficial vessels formed in skin of I, II and III fingers, medial part of foot and medial surface of shin. These vessels run along vena saphena magna and empty into superficial inguinal nodes.

Lateral group of superficial vessels of lower limb formed laterally in area of fingers in dorsal foot surface and lateral surface of shin. These vessels beneath knee join to medial group.

Posterior group of superficial vessels of lower limb starts in skin of heel and plantar surface of lateral foot margin, passes along the vena saphaena parva and runs into popliteal lymphatic nodes.

Deep vessels of lower limb drainage muscles, joints, synovial sheaths, bones, nerves, accompany deep arteries and veins and empty into deep inguinal nodes.

 

The Lymph nodes of the Lower Extremity—The Lymph nodes of the lower extremity consist of the anterior tibial node and the popliteal and inguinal nodes.

The anterior tibial node (lymphonodeula tibialis anterior) is small and inconstant. It lies on the interosseous membrane in relation to the upper part of the anterior tibial vessels, and constitutes a substation in the course of the anterior tibial lymphatic trunks.

  The popliteal nodes (lymphonodeulæ popliteæ), small in size and some six or seven in number, are imbedded in the fat contained in the popliteal fossa. One lies immediately beneath the popliteal fascia, near the terminal part of the small saphenous vein, and drains the region from which this vein derives its tributaries. Another is placed between the popliteal artery and the posterior surface of the knee-joint; it receives the lymphatic vessels from the knee-joint together with those which accompany the genicular arteries. The others lie at the sides of the popliteal vessels, and receive as efferents the trunks which accompany the anterior and posterior tibial vessels. The efferents of the popliteal nodes pass almost entirely alongside the femoral vessels to the deep inguinal nodes, but a few may accompany the great saphenous vein, and end in the nodes of the superficial subinguinal group.

  The inguinal nodes (lymphonodeulæ inguinales) (610), from twelve to twenty in number, are situated at the upper part of the femoral triangle. They may be divided into two groups by a horizontal line at the level of the termination of the great saphenous vein; those lying above this line are termed the superficial inguinal nodes, and those below it the subinguinal nodes, the latter group consisting of a superficial and a deep set.

The superficial lymph nodes and lymphatic vessels of the lower extremity.

 

  The Superficial Inguinal Nodes form a chain immediately below the inguinal ligament. They receive as afferents lymphatic vessels from the integument of the penis, scrotum, perineum, buttock, and abdominal wall below the level of the umbilicus.

  The Superficial Subinguinal Nodes (lymphonodeulæ subinguinales superficiales) are placed on either side of the upper part of the great saphenous vein; their efferents consist chiefly of the superficial lymphatic vessels of the lower extremity; but they also receive some of the vessels which drain the integument of the penis, scrotum, perineum, and buttock.

  The Deep Subinguinal Nodes (lymphonodeulæ subinguinales profundæ) vary from one to three in number, and are placed under the fascia lata, on the medial side of the femoral vein. When three are present, the lowest is situated just below the junction of the great saphenous and femoral veins, the middle in the femoral canal, and the highest in the lateral part of the femoral ring. The middle one is the most inconstant of the three, but the highest, the node of Cloquet or Rosenmüller, is also frequently absent. They receive as afferents the deep lymphatic trunks which accompany the femoral vessels, the lymphatics from the glans penis vel clitoridis, and also some of the efferents from the superficial subinguinal nodes.

 

The Lymphatic Vessels of the Lower Extremity—The lymphatic vessels of the lower extremity consist of two sets, superficial and deep, and in their distribution correspond closely with the veins.

  The superficial lymphatic vessels lie in the superficial fascia, and are divisible into two groups: a medial, which follows the course of the great saphenous vein, and a lateral, which accompanies the small saphenous vein. The vessels of the medial group are larger and more numerous than those of the lateral group, and commence on the tibial side and dorsum of the foot; they ascend both in front of and behind the medial malleolus, run up the leg with the great saphenous vein, pass with it behind the medial condyle of the femur, and accompany it to the groin, where they end in the subinguinal group of superficial nodes. The vessels of the lateral group arise from the fibular side of the foot; some ascend in front of the leg, and, just below the knee, cross the tibia to join the lymphatics on the medial side of the thigh; others pass behind the lateral malleolus, and, accompanying the small saphenous vein, enter the popliteal nodes.

  The deep lymphatic vessels are few in number, and accompany the deep bloodvessels. In the leg, they consist of three sets, the anterior tibial, posterior tibial, and peroneal, which accompany the corresponding bloodvessels, two or three with each artery; they enter the popliteal Lymph nodes.

  The deep lymphatic vessels of the gluteal and ischial regions follow the course of the corresponding bloodvessels. Those accompanying the superior gluteal vessels end in a node which lies on the intrapelvic portion of the superior gluteal artery near the upper border of the greater sciatic foramen. Those following the inferior gluteal vessels traverse one or two small nodes which lie below the Piriformis muscle, and end in the hypogastric nodes.

 

 

Lumbar spinal nerves. Lumbar plexus: composition, topography, distribution of branches

The lumbar plexus is formed from part of Th₁₂  and L₁ - L₄ ventral rami of the thoracic and lumbar spinal nerves. Lumbar plexus lies inside the psoas major muscle. The lumbar plexus gives off motor branches directly to the psoas major and psoas minor muscles, the quadratus lumborum muscle.

1.     The iliohypogastric nerve runs on the inner surface of the quadratus lumborum muscle and then between the transversus abdominus muscle and the internal oblique mus­cle of the abdomen and innervates these muscles. It gives off the lateral cutaneous branch which supplies the lateral re­gion of the hip and the cutane­ous branch for skin above the inguinal ligament.

2.     The ilioinguinal nerve runs along the inguinal ligament and takes part in the innervation of the broad abdominal muscles, the sen­sory innervation of the skin of the mons pubis, and the upper part of the scrotum or the labia majora in the female.

3.     The lateral femoral cutaneous nerve passes over the iliacus muscle to just below the anterior superior iliac spine. It then extends through the lateral part of the muscular lacuna, to the skin of lateral surface of the thigh.

4.     The femoral nerve passes on the lateral mar­gin of the psoas major muscle as far as the inguinal ligament, and through the muscular lacuna to the anterior surface of the thigh. Beneath the inguinal ligament the nerve trunk divides into a number of branches: a primarily sensory ventral group, anterior cutaneous branches for the skin of thigh, a motor branches to the anterior muscles of the thigh, and the saphenous nerve. The femoral nerve supplies the rectus femoris, the vastus medialis, lateralis and the vastus intermedius; the sartorius mus­cle. It gives off small sensory twigs to the capsule of the knee joint and vessels. The saphenous nerve runs into the adduc­tor canal. It is a purely sensory nerve and gives off an intrapatellar branch, to supply the skin below the patella. Then saphenous nerve supplies the skin on the an­terior and medial surfaces of the lower leg, the medial margin of the foot as far as the great toe.

5.     The obturator nerve supplies motor fibers to the adductor muscles (*) of the thigh. The nerve passes through the obturator canal where it extends to the thigh. It supplies a muscular branch to the obturator externus muscle and then divides into a superficial and a deep branches. Cutaneous branch to the skin of the medial surface of the thigh.

(* - adductor longus, adductor brevis mus­cles, pectineus and the gracilis muscles, ad­ductor magnus muscle).

6.     The genitofemoral nerve divides early into two branches, either in or on the psoas muscle. The genital branch passes over the inguinal ligament and innervates the cremaster muscle or the ligamentum teres and supplies the sensory innervation of the skin of the scrotum or the labia majora. The femoral branch passes below the in­guinal ligament and reaches the saphenous hiatus. It supplies the skin of the thigh lateral to the area of the genital branch.

The anterior divisions of the lumbar, sacral, and coccygeal nerves form the lumbosacral plexus, the first lumbar nerve being frequently joined by a branch from the twelfth thoracic. For descriptive purposes this plexus is usually divided into three parts—the lumbar, sacral, and pudendal plexuses.

 

The Lumbar Nerves (Nn. Lumbales)

  The anterior divisions of the lumbar nerves (rami anteriores) increase in size from above downward. They are joined, near their origins, by gray rami communicantes from the lumbar ganglia of the sympathetic trunk. These rami consist of long, slender branches which accompany the lumbar arteries around the sides of the vertebral bodies, beneath the Psoas major. Their arrangement is somewhat irregular: one ganglion may give rami to two lumbar nerves, or one lumbar nerve may receive rami from two ganglia. The first and second, and sometimes the third and fourth lumbar nerves are each connected with the lumbar part of the sympathetic trunk by a white ramus communicans.

  The nerves pass obliquely outward behind the Psoas major, or between its fasciculi, distributing filaments to it and the Quadratus lumborum. The first three and the greater part of the fourth are connected together in this situation by anastomotic loops, and form the lumbar plexus. The smaller part of the fourth joins with the fifth to form the lumbosacral trunk, which assists in the formation of the sacral plexus. The fourth nerve is named the nervus furcalis, from the fact that it is subdivided between the two plexuses. 

 

The Lumbar Plexus  (plexus lumbalis).—The lumbar plexus is formed by the loops of communication between the anterior divisions of the first three and the greater part of the fourth lumbar nerves; the first lumbar often receives a branch from the last thoracic nerve. It is situated in the posterior part of the Psoas major, in front of the transverse processes of the lumbar vertebræ.

Plan of lumbar plexus.

 

  The mode in which the plexus is arranged varies in different subjects. It differs from the brachial plexus in not forming an intricate interlacement, but the several nerves of distribution arise from one or more of the spinal nerves, in the following manner: the first lumbar nerve, frequently supplemented by a twig from the last thoracic, splits into an upper and lower branch; the upper and larger branch divides into the iliohypogastric and ilioinguinal nerves; the lower and smaller branch unites with a branch of the second lumbar to form the genitofemoral nerve. The remainder of the second nerve, and the third and fourth nerves, divide into ventral and dorsal divisions. The ventral division of the second unites with the ventral divisions of the third and fourth nerves to form the obturator nerve. The dorsal divisions of the second and third nerves divide into two branches, a smaller branch from each uniting to form the lateral femoral cutaneous nerve, and a larger branch from each joining with the dorsal division of the fourth nerve to form the femoral nerve. The accessory obturator, when it exists, is formed by the union of two small branches given off from the third and fourth nerves.

The lumbar plexus and its branches.

 

  The branches of the lumbar plexus may therefore be arranged as follows:

Iliohypogastric       1 L.

Ilioinguinal             1 L.

Genitofemoral        1, 2 L.

 

Dorsal divisions.

Lateral femoral cutaneous    2, 3 L.

Femoral                              2, 3, 4 L.

 

Ventral divisions.

Obturator                            2, 3, 4 L.

Accessory obturator            3, 4 L.

 

  The Iliohypogastric Nerve (n. iliohypogastricus) arises from the first lumbar nerve. It emerges from the upper part of the lateral border of the Psoas major, and crosses obliquely in front of the Quadratus lumborum to the iliac crest. It then perforates the posterior part of the Transversus abdominis, near the crest of the ilium, and divides between that muscle and the Obliquus internus abdominis into a lateral and an anterior cutaneous branch.

  The lateral cutaneous branch (ramus cutaneus lateralis; iliac branch) pierces the Obliqui internus and externus immediately above the iliac crest, and is distributed to the skin of the gluteal region, behind the lateral cutaneous branch of the last thoracic nerve (830); the size of this branch bears an inverse proportion to that of the lateral cutaneous branch of the last thoracic nerve.

Deep and superficial dissection of the lumbar plexus.

 

  The anterior cutaneous branch (ramus cutaneus anterior; hypogastric branch) continues onward between the Obliquus internus and Transversus. It then pierces the Obliquus internus, becomes cutaneous by perforating the aponeurosis of the Obliquus externus about 2.5 cm. above the subcutaneous inguinal ring, and is distributed to the skin of the hypogastric region.

  The iliohypogastric nerve communicates with the last thoracic and ilioinguinal nerves.

  The Ilioinguinal Nerve (n. ilioinguinalis), smaller than the preceding, arises with it from the first lumbar nerve. It emerges from the lateral border of the Psoas major just below the iliohypogastric, and, passing obliquely across the Quadratus lumborum and Iliacus, perforates the Transversus abdominis, near the anterior part of the iliac crest, and communicates with the iliohypogastric nerve between the Transversus and the Obliquus internus. The nerve then pierces the Obliquus internus, distributing filaments to it, and, accompanying the spermatic cord through the subcutaneous inguinal ring, is distributed to the skin of the upper and medial part of the thigh, to the skin over the root of the penis and upper part of the scrotum in the male, and to the skin covering the mons pubis and labium majus in the female. The size of this nerve is in inverse proportion to that of the iliohypogastric. Occasionally it is very small, and ends by joining the iliohypogastric; in such cases, a branch from the iliohypogastric takes the place of the ilioinguinal, or the latter nerve may be altogether absent.

Cutaneous nerves of right lower extremity. Front view.

 

  The Genitofemoral Nerve (n. genitofemoralis; genitocrural nerve) arises from the first and second lumbar nerves. It passes obliquely through the substance of the Psoas major, and emerges from its medial border, close to the vertebral column, opposite the fibrocartilage between the third and fourth lumbar vertebræ; it then descends on the surface of the Psoas major, under cover of the peritoneum, and divides into the external spermatic and lumboinguinal nerves. Occasionally these two nerves emerge separately through the substance of the Psoas.

  The external spermatic nerve (n. spermaticus externus; genital branch of genitofemoral) passes outward on the Psoas major, and pierces the fascia transversalis, or passes through the abdominal inguinal ring; it then descends behind the spermatic cord to the scrotum, supplies the Cremaster, and gives a few filaments to the skin of the scrotum. In the female, it accompanies the round ligament of the uterus, and is lost upon it.

  The lumboinguinal nerve (n. lumboinguinalis; femoral or crural branch of genitofemoral) descends on the external iliac artery, sending a few filaments around it, and, passing beneath the inguinal ligament, enters the sheath of the femoral vessels, lying superficial and lateral to the femoral artery. It pierces the anterior layer of the sheath of the vessels and the fascia lata, and supplies the skin of the anterior surface of the upper part of the thigh. On the front of the thigh it communicates with the anterior cutaneous branches of the femoral nerve. A few filaments from the lumboinguinal nerve may be traced to the femoral artery.

  The Lateral Femoral Cutaneous Nerve (n. cutaneus femoralis lateralis; external cutaneous nerve) arises from the dorsal divisions of the second and third lumbar nerves. It emerges from the lateral border of the Psoas major about its middle, and crosses the Iliacus obliquely, toward the anterior superior iliac spine. It then passes under the inguinal ligament and over the Sartorius muscle into the thigh, where it divides into two branches, and anterior and a posterior.

  The anterior branch becomes superficial about 10 cm. below the inguinal ligament, and divides into branches which are distributed to the skin of the anterior and lateral parts of the thigh, as far as the knee. The terminal filaments of this nerve frequently communicate with the anterior cutaneous branches of the femoral nerve, and with the infrapatellar branch of the saphenous nerve, forming with them the patellar plexus.

  The posterior branch pierces the fascia lata, and subdivides into filaments which pass backward across the lateral and posterior surfaces of the thigh, supplying the skin from the level of the greater trochanter to the middle of the thigh.

  The Obturator Nerve (n. obturatorius) arises from the ventral divisions of the second, third, and fourth lumbar nerves; the branch from the third is the largest, while that from the second is often very small. It descends through the fibers of the Psoas major, and emerges from its medial border near the brim of the pelvis; it then passes behind the common iliac vessels, and on the lateral side of the hypogastric vessels and ureter, which separate it from the ureter, and runs along the lateral wall of the lesser pelvis, above and in front of the obturator vessels, to the upper part of the obturator foramen. Here it enters the thigh, and divides into an anterior and a posterior branch, which are separated at first by some of the fibers of the Obturator externus, and lower down by the Adductor brevis.

  The anterior branch (ramus anterior) leaves the pelvis in front of the Obturator externus and descends in front of the Adductor brevis, and behind the Pectineus and Adductor longus; at the lower border of the latter muscle it communicates with the anterior cutaneous and saphenous branches of the femoral nerve, forming a kind of plexus. It then descends upon the femoral artery, to which it is finally distributed. Near the obturator foramen the nerve gives off an articular branch to the hipjoint. Behind the Pectineus, it distributes branches to the Adductor longus and Gracilis, and usually to the Adductor brevis, and in rare cases to the Pectineus; it receives a communicating branch from the accessory obturator nerve when that nerve is present.

Nerves of the right lower extremity. Front view.

 

  Occasionally the communicating branch to the anterior cutaneous and saphenous branches of the femoral is continued down, as a cutaneous branch, to the thigh and leg. When this is so, it emerges from beneath the lower border of the Adductor longus, descends along the posterior margin of the Sartorius to the medial side of the knee, where it pierces the deep fascia, communicates with the saphenous nerve, and is distributed to the skin of the tibial side of the leg as low down as its middle.

  The posterior branch (ramus posterior) pierces the anterior part of the Obturator externus, and supplies this muscle; it then passes behind the Adductor brevis on the front of the Adductor magnus, where it divides into numerous muscular branches which are distributed to the Adductor magnus and the Adductor brevis when the latter does not receive a branch from the anterior division of the nerve. It usually gives off an articular filament to the knee-joint.

  The articular branch for the knee-joint is sometimes absent; it either perforates the lower part of the Adductor magnus, or passes through the opening which transmits the femoral artery, and enters the popliteal fossa; it then descends upon the popliteal artery, as far as the back part of the knee-joint, where it perforates the oblique popliteal ligament, and is distributed to the synovial membrane. It gives filaments to the popliteal artery.

  The Accessory Obturator Nerve (n. obturatorius accessorius) is present in about 29 per cent. of cases. It is of small size, and arises from the ventral divisions of the third and fourth lumbar nerves. It descends along the medial border of the Psoas major, crosses the superior ramus of the pubis, and passes under the Pectineus, where it divides into numerous branches. One of these supplies the Pectineus, penetrating its deep surface, another is distributed to the hip-joint; while a third communicates with the anterior branch of the obturator nerve. Occasionally the accessory obturator nerve is very small and is lost in the capsule of the hip-joint. When it is absent, the hip-joint receives two branches from the obturator nerve.

  The Femoral Nerve (n. femoralis; anterior crural nerve), the largest branch of the lumbar plexus, arises from the dorsal divisions of the second, third, and fourth lumbar nerves. It descends through the fibers of the Psoas major, emerging from the muscle at the lower part of its lateral border, and passes down between it and the Iliacus, behind the iliac fascia; it then runs beneath the inguinal ligament, into the thigh, and splits into an anterior and a posterior division. Under the inguinal ligament, it is separated from the femoral artery by a portion of the Psoas major.

  Within the abdomen the femoral nerve gives off small branches to the Iliacus, and a branch which is distributed upon the upper part of the femoral artery; the latter branch may arise in the thigh.

  In the thigh the anterior division of the femoral nerve gives off anterior cutaneous and muscular branches. The anterior cutaneous branches comprise the intermediate and medial cutaneous nerves.

  The intermediate cutaneous nerve (ramus cutaneus anterior; middle cutaneous nerve) pierces the fascia lata (and generally the Sartorius) about 7.5 cm. below the inguinal ligament, and divides into two branches which descend in immediate proximity along the forepart of the thigh, to supply the skin as low as the front of the knee. Here they communicate with the medial cutaneous nerve and the infrapatellar branch of the saphenous, to form the patellar plexus. In the upper part of the thigh the lateral branch of the intermediate cutaneous communicates with the lumboinguinal branch of the genitofemoral nerve.

  The medial cutaneous nerve (ramus cutaneus anterior; internal cutaneous nerve) passes obliquely across the upper part of the sheath of the femoral artery, and divides in front, or at the medial side of that vessel, into two branches, an anterior and a posterior. The anterior branch runs downward on the Sartorius, perforates the fascia lata at the lower third of the thigh, and divides into two branches: one supplies the integument as low down as the medial side of the knee; the other crosses to the lateral side of the patella, communicating in its course with the infrapatellar branch of the saphenous nerve. The posterior branch descends along the medial border of the Sartorius muscle to the knee, where it pierces the fascia lata, communicates with the saphenous nerve, and gives off several cutaneous branches. It then passes down to supply the integument of the medial side of the leg. Beneath the fascia lata, at the lower border of the Adductor longus, it joins to form a plexiform net-work (subsartorial plexus) with branches of the saphenous and obturator nerves. When the communicating branch from the obturator nerve is large and continued to the integument of the leg, the posterior branch of the medial cutaneous is small, and terminates in the plexus, occasionally giving off a few cutaneous filaments. The medial cutaneous nerve, before dividing, gives off a few filaments, which pierce the fascia lata, to supply the integument of the medial side of the thigh, accompanying the long saphenous vein. One of these filaments passes through the saphenous opening; a second becomes subcutaneous about the middle of the thigh; a third pierces the fascia at its lower third.

 

MUSCULAR BRANCHES (rami musculares).—The nerve to the Pectineus arises immediately below the inguinal ligament, and passes behind the femoral sheath to enter the anterior surface of the muscle; it is often duplicated. The nerve to the Sartorius arises in common with the intermediate cutaneous.

  The posterior division of the femoral nerve gives off the saphenous nerve, and muscular and articular branches.

  The Saphenous Nerve (n. saphenus; long or internal saphenous nerve) is the largest cutaneous branch of the femoral nerve. It approaches the femoral artery where this vessel passes beneath the Sartorius, and lies in front of it, behind the aponeurotic covering of the adductor canal, as far as the opening in the lower part of the Adductor magnus. Here it quits the artery, and emerges from behind the lower edge of the aponeurotic covering of the canal; it descends vertically along the medial side of the knee behind the Sartorius, pierces the fascia lata, between the tendons of the Sartorius and Gracilis, and becomes subcutaneous. The nerve then passes along the tibial side of the leg, accompanied by the great saphenous vein, descends behind the medial border of the tibia, and, at the lower third of the leg, divides into two branches: one continues its course along the margin of the tibia, and ends at the ankle; the other passes in front of the ankle, and is distributed to the skin on the medial side of the foot, as far as the ball of the great toe, communicating with the medial branch of the superficial peroneal nerve.

 

BRANCHES.

  —The saphenous nerve, about the middle of the thigh, gives off a branch which joins the subsartorial plexus.

  At the medial side of the knee it gives off a large infrapatellar branch, which pierces the Sartorius and fascia lata, and is distributed to the skin in front of the patella. This nerve communicates above the knee with the anterior cutaneous branches of the femoral nerve; below the knee, with other branches of the saphenous; and, on the lateral side of the joint, with branches of the lateral femoral cutaneous nerve, forming a plexiform net-work, the plexus patellæ. The infrapatellar branch is occasionally small, and ends by joining the anterior cutaneous branches of the femoral, which supply its place in front of the knee.

  Below the knee, the branches of the saphenous nerve are distributed to the skin of the front and medial side of the leg, communicating with the cutaneous branches of the femoral, or with filaments from the obturator nerve.

  The muscular branches supply the four parts of the Quadriceps femoris. The branch to the Rectus femoris enters the upper part of the deep surface of the muscle, and supplies a filament to the hip-joint. The branch to the Vastus lateralis, of large size, accompanies the descending branch of the lateral femoral circumflex artery to the lower part of the muscle. It gives off an articular filament to the knee-joint. The branch to the Vastus medialis descends lateral to the femoral vessels in company with the saphenous nerve. It enters the muscle about its middle, and gives off a filament, which can usually be traced downward, on the surface of the muscle, to the knee-joint. The branches to the Vastus intermedius, two or three in number, enter the anterior surface of the muscle about the middle of the thigh; a filament from one of these descends through the muscle to the Articularis genu and the knee-joint. The articular branch to the hip-joint is derived from the nerve to the Rectus femoris.

  The articular branches to the knee-joint are three in number. One, a long slender filament, is derived from the nerve to the Vastus lateralis; it penetrates the capsule of the joint on its anterior aspect. Another, derived from the nerve to the Vastus medialis, can usually be traced downward on the surface of this muscle to near the joint; it then penetrates the muscular fibers, and accompanies the articular branch of the highest genicular artery, pierces the medial side of the articular capsule, and supplies the synovial membrane. The third branch is derived from the nerve to the Vastus intermedius.

 

 

Sacral and coccygeal spinal nerves. Sacral and coccygeal plexus

The sacral plexus is formed from L_IV-L_V, S_I-S_IV ventral rami of the lumbar and sacral spinal nerves. Sacral plexus lies on the piriform muscle and gives off short and long branches.

short branches:

·        small muscular branches pass directly to muscles in the pelvic region: internal obturator, superior and inferior gemelli piriform quadratus femoris muscles

·        superior gluteal nerve passes through the suprapiriform foramen to supply the motor innervation of the medius and minimus gluteus muscle and tensor fasciae latae

·        inferior gluteal nerve leaves the pelvis through the infrapiriform foramen and supplies several branches to the gluteus maximus muscle

·        pudendal nerve leaves the pelvis through the infrapiriform foramen and passes dorsally around the ischial spine to enter the ischiorectal fossa through the lesser sciatic foramen. It gives off here inferior rectal nerves to external anal sphincter, perineal nerves to ischiocavernosus, bulbospondiosus, transversi perinei superficial and profundus muscles and skin. Posterior scrotal (labial) nerves and dorsal penis (clitoridis) nerve supplies external genitals and sphincter urethrae.

long branches:

1.              Posterior femoral cutaneous nerve leaves the pelvis through the infrapiriform foramen and passes below the gluteus maximus muscle to the skin in posterior surface of the thigh. It is a purely sensory nerve and gives off branches to the lower margin of the buttocks, the inferior cluneal nerves, the perineal branches.

2.              Sciatic nerve (the largest in human body) nerve leaves the pelvis through the infrapiriform foramen and passes to­ward the knee beneath the gluteus maximus muscle and the biceps mus­cle. It supplies the long head of the biceps femoris muscle, semitendinosus and semimembranosus. Then it divides into the tibial nerve and common peroneal nerve above the knee joint.

Tibial nerve runs vertically through the middle of the popliteal fossa deep to the gastrocnemius muscle in cruropopliteal canal. The medial sural cutaneous nerve  sepa­rates in the popliteal fossa and runs downward between the two heads of the gastrocnemius muscle (supplies the skin of medial leg region) to combine with the peroneal communicating branch to form the sural nerve. This passes lateral to the Achilles tendon and behind and around the lateral malleolus to reach the lateral margin of the foot. It gives off lateral calcaneal branches to the skin of the lateral side of the heel, and the lateral dorsal cutaneous nerve to the lateral mar­gin of the foot. Motor branches of the tibial nerve arise in the popliteal fossa for: the gastrocnemius muscle, so­leus muscle and plantaris and popliteal muscles the tibialis posterior muscle, flexor digitorum longus muscles and the flexor hallucis longus also the interosseous membrane, the periosteum of the tibia, the ankle joint and tibiofibular joint. Below the medial malleolus tibial nerve divides into two terminal branches, the medial and lateral plantar nerves.

a)          The medial plantar nerve runs in the medial plantar sulcus and innervates the abductor hallucis mus­cle, the flexor digitorum brevis muscle and the flexor hallucis brevis muscles. It divides into the three common plantar digital nerves which supply lumbrical muscles 1 and 2 and divide further into the deep digital plantar nerves that sup­ply the skin of the spaces between the toes from the great to the fourth toe.

b)         The second terminal branch, the lateral plantar nerve runs in the lateral plantar sulcus, supplies the skin of the region of the small toe and to the interos­seous muscles, the adductor hal­lucis muscle and the lateral 3 and 4 lumbrical muscles, flexor digiti minimi brevis muscle.

·        Common peroneal nerve passes along the biceps muscle at the lateral margin of the popliteal fossa to the head of the fibula. It winds around the neck of the fibula toward the anterior surface of the lower leg and enters the peroneus longus muscle. Within the muscle it divides (common peroneal nerve) into the superficial and deep pero­neal nerves. The lateral sural cutaneous nerve sup­plies the skin of the lateral surface of the lower leg, and the communicating medial sural cutaneous nerve that together with the forms the sural nerve.

c)          The superficial peroneal nerve passes between the peroneus longus muscle and the fibula to the dorsum of the foot. It gives off muscular branches to the peroneus longus and brevis muscles. The remainder of the nerve is purely sensory; it divides into two terminal branches, the medial dorsal cutaneous nerve and the intermedi­ate dorsal cutaneous nerve which supply the skin of the dorsum of the foot, with the exception of the space between the great and second toes.

d)         The deep peroneal nerve, which is predominantly motor, turns anteriorly to the anterior mus­cles of the leg and passes to the dorsum of the foot. The deep peroneal nerve gives off several motor branches to the extensor muscles of the lower leg and the foot, to the tibialis anterior muscle, the extensors of the digits (lon­gus and brevis) and the extensors of the great toe (longus and brevis). The terminal branch is sensory and supplies the adjacent surfaces of the interspace between the great and second toes.

 

Coccygeal plexus

The coccygeal plexus is formed from ventral rami of the sacral and coccygeal spinal nerves (S_V , Co_I ). It is located on coccygeal muscle. Anococccygeal nerves start there and innervate the skin in adjacent area.

The anterior divisions of the sacral and coccygeal nerves (rami anteriores) form the sacral and pudendal plexuses. The anterior divisions of the upper four sacral nerves enter the pelvis through the anterior sacral foramina, that of the fifth between the sacrum and coccyx, while that of the coccygeal nerve curves forward below the rudimentary transverse process of the first piece of the coccyx. The first and second sacral nerves are large; the third, fourth, and fifth diminish progressively from above downward. Each receives a gray ramus communicans from the corresponding ganglion of the sympathetic trunk, while from the third and frequently from the second and the fourth sacral nerves, a white ramus communicans is given to the pelvic plexuses of the sympathetic.

 

The Sacral Plexus (plexus sacralis).

 

—The sacral plexus is formed by the lumbosacral trunk, the anterior division of the first, and portions of the anterior divisions of the second and third sacral nerves.

  The lumbosacral trunk comprises the whole of the anterior division of the fifth and a part of that of the fourth lumbar nerve; it appears at the medial margin of the Psoas major and runs downward over the pelvic brim to join the first sacral nerve. The anterior division of the third sacral nerve divides into an upper and a lower branch, the former entering the sacral and the latter the pudendal plexus.

  The nerves forming the sacral plexus converge toward the lower part of the greater sciatic foramen, and unite to form a flattened band, from the anterior and posterior surfaces of which several branches arise. The band itself is continued as the sciatic nerve. which splits on the back of the thigh into the tibial and common peroneal nerves; these two nerves sometimes arise separately from the plexus, and in all cases their independence can be shown by dissection.

 

Relation.—The sacral plexus lies on the back of the pelvis between the Piriformis and the pelvic fascia; in front of it are the hypogastric vessels, the ureter and the sigmoid colon. The superior gluteal vessels run between the lumbosacral trunk and the first sacral nerve, and the inferior gluteal vessels between the second and third sacral nerves.

  All the nerves entering the plexus, with the exception of the third sacral, split into ventral and dorsal divisions, and the nerves arising from these are as follows:

Ventral divisions.

Dorsal divisions.

  The Nerve to the Quadratus Femoris and Gemellus Inferior arises from the ventral divisions of the fourth and fifth lumbar and first sacral nerves: it leaves the pelvis through the greater sciatic foramen, below the Piriformis, and runs down in front of the sciatic nerve, the Gemelli, and the tendon of the Obturator internus, and enters the anterior surfaces of the muscles; it gives an articular branch to the hip-joint.

Dissection of side wall of pelvis showing sacral and pudendal plexuses.

 

  The Superior Gluteal Nerve (n. glutæus superior) arises from the dorsal divisions of the fourth and fifth lumbar and first sacral nerves: it leaves the pelvis through the greater sciatic foramen above the Piriformis, accompanied by the superior gluteal vessels, and divides into a superior and an inferior branch. The superior branch accompanies the upper branch of the deep division of the superior gluteal artery and ends in the Glutæus minimus. The inferior branch runs with the lower branch of the deep division of the superior gluteal artery across the Glutæus minimus; it gives filaments to the Glutæi medius and minimus, and ends in the Tensor fasciæ latæ.

  The Inferior Gluteal Nerve (n. glutæus inferior) arises from the dorsal divisions of the fifth lumbar and first and second sacral nerves: it leaves the pelvis through the greater sciatic foramen, below the Piriformis, and divides into branches which enter the deep surface of the Glutæus maximus.

  The Posterior Femoral Cutaneous Nerve (n. cutaneus femoralis posterior; small sciatic nerve) is distributed to the skin of the perineum and posterior surface of the thigh and leg. It arises partly from the dorsal divisions of the first and second, and from the ventral divisions of the second and third sacral nerves, and issues from the pelvis through the greater sciatic foramen below the Piriformis. It then descends beneath the Glutæus maximus with the inferior gluteal artery, and runs down the back of the thigh beneath the fascia lata, and over the long head of the Biceps femoris to the back of the knee; here it pierces the deep fascia and accompanies the small saphenous vein to about the middle of the back of the leg, its terminal twigs communicating with the sural nerve.

  Its branches are all cutaneous, and are distributed to the gluteal region, the perineum, and the back of the thigh and leg.

  The gluteal branches (nn. clunium inferiores), three or four in number, turn upward around the lower border of the Glutæus maximus, and supply the skin covering the lower and lateral part of that muscle.

  The perineal branches (rami perineales) are distributed to the skin at the upper and medial side of the thigh. One long perineal branch, inferior pudendal (long scrotal nerve), curves forward below and in front of the ischial tuberosity, pierces the fascia lata, and runs forward beneath the superficial fascia of the perineum to the skin of the scrotum in the male, and of the labium majus in the female. It communicates with the inferior hemorrhoidal and posterior scrotal nerves.

  The branches to the back of the thigh and leg consist of numerous filaments derived from both sides of the nerve, and distributed to the skin covering the back and medial side of the thigh, the popliteal fossa, and the upper part of the back of the leg.

  The Sciatic (n. ischiadicus; great sciatic nerve) supplies nearly the whole of the skin of the leg, the muscles of the back of the thigh, and those of the leg and foot. It is the largest nerve in the body, measuring 2 cm. in breadth, and is the continuation of the flattened band of the sacral plexus. It passes out of the pelvis through the greater sciatic foramen, below the Piriformis muscle. It descends between the greater trochanter of the femur and the tuberosity of the ischium, and along the back of the thigh to about its lower third, where it divides into two large branches, the tibial and common peroneal nerves. This division may take place at any point between the sacral plexus and the lower third of the thigh. When it occurs at the plexus, the common peroneal nerve usually pierces the Piriformis.

  In the upper part of its course the nerve rests upon the posterior surface of the ischium, the nerve to the Quadratus femoris, the Obturator internus and Gemelli, and the Quadratus femoris; it is accompanied by the posterior femoral cutaneous nerve and the inferior gluteal artery, and is covered by the Glutæus maximus. Lower down, it lies upon the Adductor magnus, and is crossed obliquely by the long head of the Biceps femoris.

  The nerve gives off articular and muscular branches.

  The articular branches (rami articulares) arise from the upper part of the nerve and supply the hip-joint, perforating the posterior part of its capsule; they are sometimes derived from the sacral plexus.

  The muscular branches (rami musculares) are distributed to the Biceps femoris, Semitendinosus, Semimembranosus, and Adductor magnus. The nerve to the short head of the Biceps femoris comes from the common peroneal part of the sciatic, while the other muscular branches arise from the tibial portion, as may be seen in those cases where there is a high division of the sciatic nerve.

  The Tibial Nerve (n. tibialis; internal popliteal nerve) the larger of the two terminal branches of the sciatic, arises from the anterior branches of the fourth and fifth lumbar and first, second, and third sacral nerves. It descends along the back of the thigh and through the middle of the popliteal fossa, to the lower part of the Popliteus muscle, where it passes with the popliteal artery beneath the arch of the Soleus. It then runs along the back of the leg with the posterior tibial vessels to the interval between the medial malleolus and the heel, where it divides beneath the laciniate ligament into the medial and lateral plantar nerves. In the thigh it is overlapped by the hamstring muscles above, and then becomes more superficial, and lies lateral to, and some distance from, the popliteal vessels;opposite the knee-joint, it is in close relation with these vessels, and crosses to the medial side of the artery. In the leg it is covered in the upper part of its course by the muscles of the calf; lower down by the skin, the superficial and deep fasciæ. It is placed on the deep muscles, and lies at first to the medial side of the posterior tibial artery, but soon crosses that vessel and descends on its lateral side as far as the ankle. In the lower third of the leg it runs parallel with the medial margin of the tendo calcaneus.

Diagram of the segmental distribution of the cutaneous nerves of the right lower extremity. Posterior view.

 

  The branches of this nerve are: articular, muscular, medial sural cutaneous, medial calcaneal, medial and lateral plantar.

  Articular branches (rami articulares), usually three in number, supply the knee-joint; two of these accompany the superior and inferior medial genicular arteries; and a third, the middle genicular artery. Just above the bifurcation of the nerve an articular branch is given off to the ankle-joint.

  Muscular branches (rami musculares), four or five in number, arise from the nerve as it lies between the two heads of the Gastrocnemius muscle; they supply that muscle, and the Plantaris, Soleus, and Popliteus. The branch for the Popliteus turns around the lower border and is distributed to the deep surface of the muscle. Lower down, muscular branches arise separately or by a common trunk and supply the Soleus, Tibialis posterior, Flexor digitorum longus, and Flexor hallucis longus; the branch to the last muscle accompanies the peroneal artery; that to the Soleus enters the deep surface of the muscle.

  The medial sural cutaneous nerve (n. cutaneus suræ medialis; n. communicans tibialis) descends between the two heads of the Gastrocnemius, and, about the middle of the back of the leg, pierces the deep fascia, and unites with the anastomotic ramus of the common peroneal to form the sural nerve.

The plantar nerves.

Deep nerves of the front of the leg.

 

  The medial terminal branch (internal branch) accompanies the dorsalis pedis artery along the dorsum of the foot, and, at the first interosseous space, divides into two dorsal digital nerves (nn. digitales dorsales hallucis lateralis et digiti secundi medialis) which supply the adjacent sides of the great and second toes, communicating with the medial dorsal cutaneous branch of the superficial peroneal nerve. Before it divides it gives off to the first space an interosseous branch which supplies the metatarsophalangeal joint of the great toe and sends a filament to the first Interosseous dorsalis muscle.

  The Superficial Peroneal Nerve (n. peronæus superficialis; musculocutaneous nerve) supplies the Peronei longus and brevis and the skin over the greater part of the dorsum of the foot. It passes forward between the Peronæi and the Extensor digitorum longus, pierces the deep fascia at the lower third of the leg, and divides into a medial and an intermediate dorsal cutaneous nerve. In its course between the muscles, the nerve gives off muscular branches to the Peronæi longus and brevis, and cutaneous filaments to the integument of the lower part of the leg.

Sacral plexus of the right side.

 

  The Perforating Cutaneous Nerve (n. clunium inferior medialis) usually arises from the posterior surface of the second and third sacral nerves. It pierces the lower part of the sacrotuberous ligament, and winding around the inferior border of the Glutæus maximus supplies the skin covering the medial and lower parts of that muscle.

  The perforating cutaneous nerve may arise from the pudendal or it may be absent; in the latter case its place may be taken by a branch from the posterior femoral cutaneous nerve or by a branch from the third and fourth, or fourth and fifth, sacral nerves.

  The Pudendal Nerve (n. pudendus; internal pudic nerve) derives its fibers from the ventral branches of the second, third, and fourth sacral nerves. It passes between the Piriformis and Coccygeus muscles and leaves the pelvis through the lower part of the greater sciatic foramen. It then crosses the spine of the ischium, and reënters the pelvis through the lesser sciatic foramen. It accompanies the internal pudendal vessels upward and forward along the lateral wall of the ischiorectal fossa, being contained in a sheath of the obturator fascia termed Alcock’s canal, and divides into two terminal branches, viz., the perineal nerve, and the dorsal nerve of the penis or clitoris. Before its division it gives off the inferior hemorrhoidal nerve.

  The inferior hemorrhoidal nerve (n. hæmorrhoidalis inferior) occasionally arises directly from the sacral plexus; it crosses the ischiorectal fossa, with the inferior hemorrhoidal vessels, toward the anal canal and the lower end of the rectum, and is distributed to the Sphincter ani externus and to the integument around the anus. Branches of this nerve communicate with the perineal branch of the posterior femoral cutaneous and with the posterior scrotal nerves at the forepart of the perineum.

  The perineal nerve (n. perinei), the inferior and larger of the two terminal branches of the pudendal, is situated below the internal pudendal artery. It accompanies the perineal artery and divides into posterior scrotal (or labial) and muscular branches.

  The posterior scrotal (or labial) branches (nn. scrotales (or labiales) posteriores; superficial peroneal nerves) are two in number, medial and lateral. They pierce the fascia of the urogenital diaphragm, and run forward along the lateral part of the urethral triangle in company with the posterior scrotal branches of the perineal artery; they are distributed to the skin of the scrotum and communicate with the perineal branch of the posterior femoral cutaneous nerve. These nerves supply the labium majus in the female.

  The muscular branches are distributed to the Transversus perinæi superficialis, Bulbocavernous, Ischiocavernosus, and Constrictor urethræ. A branch, the nerve to the bulb, given off from the nerve to the Bulbocavernosus, pierces this muscle, and supplies the corpus cavernosum urethræ, ending in the mucous membrane of the urethra.

  The dorsal nerve of the penis (n. dorsalis penis) is the deepest division of the pudendal nerve; it accompanies the internal pudendal artery along the ramus of the ischium; it then runs forward along the margin of the inferior ramus of the pubis, between the superior and inferior layers of the fascia of the urogenital diaphragm. Piercing the inferior layer it gives a branch to the corpus cavernosum penis, and passes forward, in company with the dorsal artery of the penis, between the layers of the suspensory ligament, on to the dorsum of the penis, and ends on the glans penis. In the female this nerve is very small, and supplies the clitoris (n. dorsalis clitoridis).

  The Visceral Branches arise from the third and fourth, and sometimes from the second, sacral nerves, and are distributed to the bladder and rectum and, in the female, to the vagina; they communicate with the pelvic plexuses of the sympathetic.

  The Muscular Branches are derived from the fourth sacral, and supply the Levator ani, Coccygeus, and Sphincter ani externus. The branches to the Levator ani and Coccygeus enter their pelvic surfaces; that to the Sphincter ani externus (perineal branch) reaches the ischiorectal fossa by piercing the Coccygeus or by passing between it and the Levator ani. Cutaneous filaments from this branch supply the skin between the anus and the coccyx.

 

Anococcygeal Nerves (nn. anococcygei).—The fifth sacral nerve receives a communicating filament from the fourth, and unites with the coccygeal nerve to form the coccygeal plexus. From this plexus the anococcygeal nerves take origin; they consist of a few fine filaments which pierce the sacrotuberous ligament to supply the skin in the region of the coccyx.

                                                                                                                                                                                                                                Prepared by  

Reminetskyy B.Y.

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