Lower limb movements include hip extension, hip flexion, knee flexion, knee extension, ankle inversion, ankle, eversion dorsiflexion and plantarflexion. All of these movements (aside from hip extension) are caused by nerves that arise from the lumbar plexus. It gives of 5 major branches that innervate thigh muscles and supply sensation to the thigh and genitalia. 

The Lumbar Plexus is the nerve plexus of the lower limb. It arises from the ventral rami of the L1-L4 nerve roots, deep to the psoas major muscle. The Iliohypogastric (L1) arises from the first lumbar nerve, and emerges as a common trunk with the Ilioinguinal nerve. After the Ilioinguinal nerve branches off, it continues to run along the anterior surface of quadratus lumborum (the muscle of the posterior abdominal wall) but still runs posterior to the kidney. It will continue to travel along its course and will pierce the transversus abdominis and internal oblique muscles. It eventually will descend down the abdominal wall to pass obliquely downwards and becomes more and more superficial. It eventually pierces the external oblique aponeurosis to give off many cutaneous branches to the skin of the pubic region. The Ilioinguinal (L1) is a nerve that enters the abdomen posterior to the arcuate ligament, and runs parallel to the iliac crests, and runs along the quadratus lumborum muscle on the posterior abdominal wall. It often crossed the iliacus muscle, and passes to the anterior end of the iliac crest. Here the nerve pierces the internal oblique and transversus abdominis muscle, and enters the inguinal canal via the deep ring. The nerve leaves the superficial inguinal ring and pierces the external spermatic fascia in order to terminate as a subcutaneous nerve.

 

The Genitofemoral (L1-2) emerges through the psoas major muscle, and passes posterior to the ureter and gonadal vessels. The nerve passes downwards and pierces the psoas major fascia just superior to the inguinal ligament. It divides into femoral and genital branches. The femoral branch pierces the femoral sheath and fascia lata, and supplies sensation to the skin of the groin inferior to the middle of the inguinal ligament. The genital branch runs with the spermatic cord and supplies motor innervation to the cremaster muscle, and cutaneous sensation to the superior part of the scrotum.

 

The Lateral femoral cutaneous (L2-3) nerve provides sensation to the lateral surface of the thigh. It emerges just above the inguinal ligament, and enters the fibrous compartment just medial to the anterior superior iliac spine. It runs superficial to the Sartorius muscle and divides into anterior and posterior branches. The anterior branch supplies sensation to the anterolateral thigh, and the posterior branch supplies sensation to the posterolateral thigh as well as the iliotibial tract. 

 

The Obturator (L2-4, anterior divisions) nerve descends medial to the psoas major muscle and innervates the medial compartment of the thigh. The anterior division supplies the adductor longus, brevis and gracilis, as well as the skin of the medial thigh. The posterior division innervates obturator externus, adductor magnus and provides an articular branch that pierces the oblique popliteal ligament. Finally the Femoral (L2-4, posterior divisions) emerges just inferior to the anterior superior iliac spine and the inguinal ligament. The nerve runs lateral to the femoral artery and vein, and supplies the anterior compartment of the thigh i.e. quadriceps femoris (vastus medialis, vastus lateralis, vastus intermedius and rectus femoris). The nerve also gives rise to the anterior and medial cutaneous nerves of the thigh. The Lumbosacral trunk (L4, L5) contributes to the sacral plexus.

Developmental precursor

Alar and basal plate of L1-L4 spinal nerves

Nerve roots- anterior rami of L1-L4

Branches- Iliohypogastric nerve, Ilioinguinal nerve, Genitofemoral nerve, lateral femoral cutaneous nerve, Obturator nerve, Femoral nerve

 

Muscles supplied

Iliohypogastric- Transversus abdominis and internal oblique

Genitofemoral- Cremaster muscle

Obdurator- Adductor magnus (adductor head), adductor longus, adductor brevis, gracilis

Femoral- Quadriceps, iliacus, Sartorius, pectineus

 

Dermatome

Ilioinguinal- Upper part of the scrotum and root of the penis in men, skin over anterior 1/3^rd of labia majora and root of the clitoris.

Iliohypogastric- Lateral cutaneous branch supplies superior buttock, anterior branch supplies the lower rectus abdominis and the mons pubis.

Genitofemoral- Femoral branch supplies sensation to the superomedial thigh. Genital branch supplies sensation to mons pubis.

Obdurator- Femoral- Medial and intermediate thigh, medial leg (saphenous nerve)

I twice Get Lunch On Fridays (the twice implies two nerves beginning with I, and does not stand for a separate nerve)

 

Iliohypogastric (I twice), L1

Ilioinguinal (I twice), L1

 

Genitofemoral (Get) L1,2

 

Lateral femoral cutaneous (Lunch) L2,3

 

Obturator (On) L2-4

 

Femoral (Fridays) L2-4

The lumbar plexus is the nerve plexus of the lower limb. It gives of 5 major branches that innervate thigh muscles and supply sensation to the thigh and genitalia. 

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