The lumbar plexus is a network of nerve fibres that gives the skin and musculature of the lower limb. That is situated in the lumbar region, in ~ the substance of the psoas major muscle and anterior come the transverse processes of the lumbar vertebrae.

You are watching: The obturator and femoral nerves branch from this plexus.

The plexus is formed by the anterior rami (divisions) that the lumbar spinal nerves L1, L2, L3 and also L4. It likewise receives contribute from thoracic spinal nerve 12. In this article, we shall look at the anatomy the the lumbar plexus – its formation and significant branches.


Spinal Nerves

The spinal nerves L1 – L4 kind the communication of the lumbar plexus. At every vertebral level, paired spinal nerves leave the spinal cord via the intervertebral foramina of the vertebral column. Every nerve climate divides right into anterior and also posterior nerve fibres.

The lumbar plexus begins as the anterior fibres that the spinal nerves L1, L2, L3, and also L4.


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Fig 1.0 – The spinal cord outflow at every vertebral level. The anterior rami of vertebral levels L1-L4 comprise the root of the lumbar plexus


The Branches


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Fig 1.1 – The right lumbar plexus, and the left sacral plexus.


The anterior rami the the L1-L4 spinal roots divide right into several cords. These cords then integrate together to kind the six major peripheral nerves that the lumbar plexus. These nerves then descend down the posterior abdominal wall to reach the reduced limb, whereby they innervate their target structures.

We shall now think about the branches the the lumbar plexus. (Note: In this article we shall include only brief notes on the duty of this nerves – for more detailed information click the title to visit their particular pages)

Iliohypogastric Nerve

The iliohypogastric nerve is the very first major branch of the lumbar plexus. It operation to the iliac crest, across the quadratus lumborum muscle of the posterior ab wall. It then perforates the transversus abdominis, and also divides right into its terminal branches.

Roots: L1 (with contribute from T12).

Motor Functions: Innervates the inner oblique and transversus abdominis.

Sensory Functions: Innervates the posterolateral gluteal skin in the pubic region. (Tip: an easy means to remember the the IlioHypogastric comes prior to the IlioInguinal is that H comes before I in the alphabet!)


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Fig 1.2 – source of the iliohypogastric nerve.


Ilioinguinal Nerve

The ilioinguinal nerve adheres to the same anatomical course as the bigger iliohypogastric nerve. After ~ innervating the muscles of the anterior ab wall, that passes through the superficial inguinal ring come innervate the skin of the genitalia and middle thigh.

Roots: L1.

Motor Functions: Innervates the inner oblique and also transversus abdominis.

Sensory Functions: Innervates the skin ~ above the premium antero-medial thigh. In males, it likewise supplies the skin over the root of the penis and also anterior scrotum. In females, it provides the skin end mons pubis and labia majora.


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Fig 1.3 – derivation of the ilioinguinal nerve.


Genitofemoral Nerve

After leaving the psoas significant muscle, the genitofemoral nerve conveniently divides right into a genital branch, and also a femoral branch.

Roots: L1, L2.

Motor Functions: The genital branch innervates the cremasteric muscle.

Sensory Functions: The genital branch innervates the skin the the anterior scrotum (in males) or the skin end mons pubis and labia majora (in females). The femoral branch innervates the skin on the upper anterior thigh.


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Fig 1.4 – derivation of the genitofemoral nerve.


Lateral Cutaneous Nerve the the Thigh

This nerve has a completely sensory function. That enters the thigh in ~ the lateral aspect of the inguinal ligament, where it provides cutaneous innervation to the skin there.

Roots: L2, L3

Motor Functions: None.

Sensory Functions: Innervates the anterior and also lateral thigh down to the level the the knee.


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Fig 1.5 – derivation of the lateral cutaneous nerve of thigh.


Obturator Nerve

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Roots: L2, L3, L4.

Motor Functions: Innervates the muscles of the medial thigh – the obturator externus, adductor longus, adductor brevis, adductor magnus and gracilis.

Sensory Functions: Innervates the skin over the medial thigh.


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Fig 1.6 – derivation of the obturator nerve.


Femoral Nerve

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Roots: L2, L3, L4.

Motor Functions: Innervates the muscle of the anterior thigh – the illiacus, pectineus, sartorius and also quadriceps femoris.

Sensory Functions: Innervates the skin ~ above the anterior thigh and the medial leg.


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Fig 1.7 – source of the femoral nerve


Note: A useful memory assist for the branches of the lumbar plexus is: I, I Get Leftovers On Fridays. This represents the Iliohypogastric, Ilioinguinal, Genitofemoral, Lateral cutaneous nerve the the thigh, Obturator and Femoral.


Clinical relationship – Lumbosacral Plexopathy

A lumbosacral plexopathy is a disorder affecting one of two people the lumbar or sacral plexus the nerves. They space rare syndromes, brought about by damages to the nerve bundles.

A plexopathy is doubt if the symptoms can not be localised to a single nerve. Patients may complain that neuropathic pains, numbness or weakness and wasting that muscles.

One that the main reasons of lumbosacral plexopathy is diabetic amyotrophy, likewise known as lumbosacral radioplexus neurophagy. In this condition, the high blood sugar levels damage the nerves.

See more: What Is The Another Term For An Icv Is The Full Form Of Icv?

Idiopathic plexopathy is an additional cause, gift the lumbosacral equivalent of Parsonage-Turner syndrome (which affects the brachial plexus). Tumours and also other local invasions can reason the plexopathy because of the compression the the plexus.

Treatment counts on what is bring about the symptoms. For tumours and also space-occupying lesions, they need to be gotten rid of if possible. For diabetic and idiopathic causes, treatment with high-dose corticosteroids have the right to be useful.