Upper Extremity . In human anatomy, the lower limb or pelvis is each one of the extremities attached to the trunk at the level of the pelvis – hip joints – through the pelvic girdle. Colloquially, the lower limbs are the legs.
Summary
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- 1 lumbosacral plexus.
- 2 Main nerve trunks of the lower limb.
- 1 Femoral or femoral nerve.
- 2 Obturator nerve.
- 3 Superior gluteal nerve.
- 4 Inferior gluteal nerve.
- 5 Tibial or internal popliteal sciatic nerve.
- 6 Peroneal nerve or external popliteal sciatic.
- 3 Arteries and veins of the lower limb.
- 4 Arteries and veins of the lower limb.
- 5 Source
Lumbosacral plexus.
The motor innervation of the lower limb depends on the lumbar (L1-L4) and sacrum (L5-S3) plexuses. There are fascicles that carry fibers from L4 and L5 to the plexosacral, so it can be called the lumbosacral plexus. The neuromuscular systems of the lower limb depend on these plexuses.
The lumbar plexus originates the femoral nerve and the obturator nerve, innervating the musculature of the anterior and medial compartment of the thigh. They have multiple direct branches, but the most important are:
- Lateral femorocutaneous nerve: it is a sensitive nerve, which originates from the L2 and L3 roots. It crosses the psoas muscle to go to the lower limb, spreading over the anterolateral aspect of the thigh. Its compression, frequent in obese people at the level of the anterior superior iliac spine, causes a picture, called meralgia paresthetica, characterized by paresthesias on the outer aspect of the thigh.
- Iliohypogastric and ilioinguinal nerves (major and minor abdominogenital, respectively): branches of the L1 root. They give sensitive innervation to the skin of the hypogastric, gluteal, inguinal and scrotum or labia majora.
The sacral plexus forms the superior gluteal, inferior gluteal, tibial, and peroneal nerves. Through the pudendal nerve it innervates the muscles of the perineum and gives sensory innervation to the external genitalia and ends the dorsal nerve of the penis or clitoris.
It gives direct branches for the pyramidal muscle, internal obturator, superior and inferior gemini, and femoral square. These muscles are located on the posterior aspect of the hip and produce external rotation and, except for the femoral square, flexion separation of the hip. The pyramidal or piriformis muscle originates from the anterior aspect of the sacrum, passes through the greater sciatic foramen, and is inserted into the greater trochanter of the femur. Under its path the common sciatic nerve comes out.
Main nervous trunks of the lower limb.
Femoral or femoral nerve.
It supplies the muscles that flex the hip and extend the knee. Innervates the psoasiliac, the quadriceps (MIR 95-96F, 96), sartorius and part of the pectineum.
The psoas-iliac (formed by the psoas major and iliac) is the main flexor of the thigh and contributes to trunk flexion, external rotation of the hip and allows us to lift the trunk from the supine position.
The quadriceps muscle, which occupies the anterior region of the thigh, is made up of the vastus rectum (intermediate, medial, and lateral) and the knee joint muscle (which stretches the joint capsule so that it is not pinched in extension). These muscles constitute a broad joint tendon for insertion into the patella called the quadriceps tendon, and the fibers that continue are inserted into the anterior tuberosity of the tibia, forming the patellar tendon. The quadriceps is the main extensor of the knee and the anterior rectum, as it originates from the anterior superior iliac spine, it is also the hip flexor.
Adductors duct.
The sartorius muscle is the most superficial muscle in the anterior compartment of the thigh and the longest in the body. It receives this name because it is the one that allows us to cross our legs “like tailors”, by performing flexion, abduction and lateral rotation movements on the hip joint. Along with the graceful (or internal rectum) and semitendinosus muscles it forms the superficial goose paw. Between the superficial (insertion of the sartorius) and deep (insertion of graceful and semitendinosus) planes there is a serous pouch that is called the anserine pouch.
The deep goose paw is formed by the insertion of the semimembranosus tendon, which underneath the medial lateral ligament is divided into three parts: the first is directed to the medial condyle of the tibia, the second is confused with the popliteal fascia, and the The third passes through the posterior aspect of the knee to form the oblique popliteal ligament.
Under the sartorius muscle is the duct of the adductors or Hunter, which connects the anterior aspect of the thigh with the popliteal socket. It measures approximately 15 cm and is limited by the internal vastus and the greater and longer approximators. Inside it run the saphenous nerve, the femoral artery and the femoral vein. The saphenous nerve is sensitive and is the largest cutaneous branch of the femoral nerve.
The sensory territory of the femoral nerve includes the anterior and medial distal faces of the thigh as well as, through its terminal branch (saphenous nerve), the medial aspect of the knee and leg. Her injury limits hip flexion and knee extension. Saphenous neuritis is known as gonalgia paresthetica or minor causalgia and is a frequent cause of pain on the medial side of the knee.
Adductors duct.
Obturator nerve.
The obturator nerve supplies the musculature of the inner aspect of the thigh, formed by the major adductor, long adductor, short adductor, graceful (or internal rectum), external obturator and pectineum. The greater adductor is also partially innervated by the internal popliteal tibial or sciatic nerve, and the pectineum is also innervated by the femoral nerve.
It picks up the sensitivity of the lower third of the inner thigh and in the hip directs the movements of approach and medial rotation (except the external obturator muscle, which performs external rotation). In the knee the internal rectum or graceful produces flexion and internal rotation. His injury limits the approach and internal rotation of the hip.
Superior gluteal nerve.
It supplies the gluteus medius and minor muscles and the tensor fascia latae. The gluteus medius is the main hip separator.
The fascia lata is the deep fascia of the thigh and embraces the thigh muscles as an elastic stocking, in a way that improves the function of all of them and prevents the protrusion of their fibers. The lateral portion of this fascia is very robust and is called the iliotibial tract or band and ends up inserting itself into the lateral condyle of the tibia. The tensor fascia lata muscle tightens the fascia and attracts the iliotibial band, enhancing the function of the femoral muscles and preventing the gluteus maximus from moving the band backward when performing leg extension.
Injury to this nerve causes gluteal insufficiency and the Trendelenburg gait in which, due to weakness of the separating musculature of the hip, during gait, when the lower limb is raised on the healthy side, the hip tilts to that side (MIR 98 -99, 94).
Inferior gluteal nerve.
It exclusively supplies the gluteus maximus. It is an external hip extensor and rotator and prevents forward pelvic tilt. Between the muscle and its insertion into the greater trochanter is a large serous pouch, the trochanteric pouch . Paralysis of this muscle results in weakness for hip extension and difficulty in ambulation.
Tibial or internal popliteal sciatic nerve.
It is the medial terminal branch of the sciatic nerve and can originate independently from ventral branches of the sacral plexus. This neuromuscular system includes muscles located in the three segments of the lower limb:
- Thigh: innervates the long portion of the biceps femoris (the short portion depends on the peroneal nerve), the semitendinosus, the semimembrane, and the ischial fibers of the greater proximator. The first three form the hamstring corsage . They all take care of the hip extension. The biceps is an external rotator and the semitendinosus and semi-membrane are internal rotators.
- Leg: innervates the muscles of the posterior compartment of the leg. This compartment is divided into two halves: shallow and deep. The deep posterior compartment is made up of the posterior tibial, flexor digitorum longus and flexor digitorum longus muscles. They are responsible for plantar flexion of the ankle and flexion of the toes. The long flexor of the first toe and the posterior tibial bone contribute to the maintenance of the arches of the foot. The posterior tibial is involved in reversal movements.
The superficial posterior compartment is made up of the soleus, calf muscles, thin plantar and popliteal muscles. They contribute to knee flexion. The popliteal is also an internal rotator. The soleus muscle performs the plantar flexion of the ankle (although it does not belong to the deep compartment) and together with the twins it composes a muscle group called the triceps sura, which are inserted distally through the Achilles tendon (MIR 95-96F, 100).
Leg compartments.
- Foot: practically all the muscles of the foot (except the extensor) belong to this system: plantar square, lumbricals, interossei, flexor digitorum brevis, muscles of the first toe (short approximator, flexor-short and spacer) and the fifth toe (opponent , flexor short and spacer).
At the level of the popliteal fossa, the medial sural cutaneous nerve originates, which descends to approximately half of the internal aspect of the leg and anastomoses with a communicating branch of the peroneal nerve, forming the sural nerve. Along with the minor saphenous vein, it descends behind the medial malleolus and innervates the lateral aspect of the ankle and foot.
Peroneal nerve or external popliteal sciatic.
It is the smallest and lateral branch of the sacral plexus. It comes out next to the tibial nerve, which it accompanies on its journey (where it supplies the short portion of the biceps femoris) until it reaches the popliteal hollow. There it is separated from the tibial and is directed towards the external aspect of the leg so that, approximately at the level of the neck of the fibula, it divides into two: superficial and deep.
The superficial peroneal nerve or cutaneous muscle is directed towards the lateral compartment of the leg and supplies the long and short lateral peroneal muscles, which are responsible for the eversion of the foot. The long lateral fibula contributes to the support of the longitudinal and transverse arches of the foot.
The deep or anterior tibial branch enters the anterior compartment of the leg and supplies the anterior tibial muscles, the extensor digitorum longus, the extensor digitorum longus and the third peroneum. They are in charge of dorsal flexion or ankle extension. The tibialis anterior produces inversion and contributes to the support of the transverse arch of the foot, together with the long fibula. The third fibula collaborates in the eversion movements of the lateral compartment.
At the level of the popliteal hollow, it forms the lateral sural cutaneous nerve that supplies the calf and a communicating fibular branch that forms the sural nerve. The common peroneal nerve is the most affected in trauma to the lower limb, especially at the level of the neck of the fibula, causing loss of dorsiflexor and eversor musculature. This injury causes a fallen or equine foot and a gait “in step”.
Lower limb arteries and veins.
The superficial peroneal nerve or cutaneous muscle is directed towards the lateral compartment of the leg and supplies the long and short lateral peroneal muscles, which are responsible for the eversion of the foot. The long lateral fibula contributes to the support of the longitudinal and transverse arches of the foot.
The deep or anterior tibial branch enters the anterior compartment of the leg and supplies the anterior tibial muscles, the extensor digitorum longus, the extensor digitorum longus and the third peroneum. They are in charge of dorsal flexion or ankle extension. The tibialis anterior produces inversion and contributes to the support of the transverse arch of the foot, together with the long fibula. The third fibula collaborates in the eversion movements of the lateral compartment.
At the level of the popliteal hollow, it forms the lateral sural cutaneous nerve that supplies the calf and a communicating fibular branch that forms the sural nerve. The common peroneal nerve is the most affected in trauma to the lower limb, especially at the level of the neck of the fibula, causing loss of dorsiflexor and eversor musculature. This injury causes a fallen or equine foot and a gait “in step”.
Lower limb arteries and veins.
The irrigation of the gluteal region comes from the gluteal arteries. The superior gluteal artery is the largest in size and is a direct branch of the hypogastric artery (internal iliac artery). It exits through the suprapyriform foramen and in the gluteal region it divides into a deep branch (for the gluteus minimus and medius muscles) and a superficial branch (for the gluteus maximus muscle).
The hypogastric artery continues with the femoral artery from its exit through the inguinal opening. The artery enters the femoral triangle under the inguinal ligament, between the iliopectineal band and the femoral vein, which at this level is medial to the artery (see inguinocrural region).
The femoral or Scarpa triangle is a triangle that has as its base the inguinal ligament and as sides the edges of the major approximator muscles inside and sartorius outside. The floor of the triangle is made up (from medial to lateral) of the long approximator, the pectineus and the iliopsoas, where the artery, vein and femoral nerve are located. There are also the lateral femorocutaneous nerve (collects the sensitivity of the lateral aspect of the thigh), the femoral branch of the genitofemoral nerve, and some vessels and lymph nodes. The femoral artery supplies the lower portion of the abdominal wall and the inguinal region.
The deep femoral artery exits the femoral triangle and descends behind the major approximator muscle, emitting the perforating and circumflex sfemoral arteries. It is the main artery of the thigh supplying the thigh, hip and muscles. The superficial femoral artery runs through the femoral triangle and enters the duct of the adductors or Hunter without giving branches to the thigh. At its exit, it continues with the popliteal artery that supplies most of the knee and is accompanied outside the vein of the same name. It continues with the tibioperoneal artery at the level of the popliteal muscle and is divided into the anterior tibial, posterior tibial, and fibular arteries that are responsible for irrigation of the leg and foot.
The blood of all the lower limbs is collected by the external iliac vein through a superficial and a deep system. The deep venous system is twofold, with numerous anastomoses that join them and accompany the arteries. The superficial venous system is formed by the major or internal saphenous vein and the minor or external saphenous vein. The major saphenous vein begins at the medial end of the dorsal venous arch of the foot and runs in front of the internal malleolus along with the saphenous nerve. Then it ascends obliquely to the medial aspect of the knee and runs along the inner aspect of the thigh until reaching the femoral triangle, where it empties into the femoral vein (MIR 94-95, 248).
Venous drainage from the lower limb.
The minor saphenous vein passes behind the external malleolus and ascends along the sural nerve on the external aspect of the leg until it reaches the popliteal fossa, where it is inserted to empty into the popliteal vein.
There are numerous anastomoses between the territories of both veins. There are vessels that connect the superficial venous system with the deep one that are called perforating vessels. They form a series of groups that are named after the author who first described them. The most important are: Dodd perforators (in the duct of the adductors), Boyd (next to the anterior tuberosity of the tibia), Cockett (medial aspect of the leg) and Kuster (region of malleoli and tibial fibula).
