The lumbar nerves are the five pairs of
spinal nerves
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into ...
emerging from the
lumbar vertebrae
The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe t ...
. They are divided into posterior and anterior divisions.
Structure
The lumbar nerves are five
spinal nerve
A spinal nerve is a mixed nerve, which carries Motor neuron, motor, Sensory neuron, sensory, and Autonomic nervous system, autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each s ...
s which arise from either side of the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...
below the
thoracic spinal cord and above the
sacral spinal cord. They arise from the spinal cord between each pair of lumbar
spinal vertebrae and travel through the
intervertebral foramina. The nerves then split into an
anterior branch, which travels forward, and a
posterior branch, which travels backwards and supplies the area of the back.
Posterior divisions
The middle divisions of the posterior branches run close to the articular processes of the vertebrae and end in the
multifidus muscle
The multifidus (multifidus spinae; : ''multifidi'') muscle consists of a number of fleshy and tendinous fasciculi, which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis. While very thin, ...
. The outer branches supply the
erector spinae muscles
The erector spinae ( ) or spinal erectors is a set of muscles that straighten and rotate the back. The spinal erectors work together with the glutes ( gluteus maximus, gluteus medius and gluteus minimus) to maintain stable posture standing or ...
.
The nerves give off branches to the skin. These pierce the
aponeurosis
An aponeurosis (; : aponeuroses) is a flattened tendon by which muscle attaches to bone or fascia. Aponeuroses exhibit an ordered arrangement of collagen fibres, thus attaining high tensile strength in a particular direction while being vulnerable ...
of the
greater trochanter.
Anterior divisions
The anterior divisions of the lumbar nerves () increase in size from above downward.
The anterior divisions communicate with the
sympathetic trunk. Near the origin of the divisions, they are joined by
gray rami communicantes from the
lumbar ganglia
The lumbar ganglia are paravertebral ganglia located in the inferior portion of the sympathetic trunk. The lumbar portion of the sympathetic trunk typically has 4 lumbar ganglia. The lumbar splanchnic nerves arise from the Ganglion, ganglia here, ...
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
The psoas major ( or ; from ) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis. It joins the iliacus muscle to form the iliopsoas. In other animals, this muscle is e ...
. Their arrangement is somewhat irregular: one ganglion may give rami to two lumbar nerves, or one lumbar nerve may receive
rami (branches) from two
ganglia
A ganglion (: ganglia) is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system, this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system, there a ...
. 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
The psoas major ( or ; from ) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis. It joins the iliacus muscle to form the iliopsoas. In other animals, this muscle is e ...
, or between its
fasciculi, distributing filaments to it and the
Quadratus lumborum.
As the nerves travel forward, they create
nervous plexuses. The first three lumbar nerves, and the greater part of the fourth together form the
lumbar plexus
The lumbar plexus is a web of nerves (a nerve plexus) in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1–L4) and from contributions of the su ...
. 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
furcal nerve, from the fact that it is subdivided between the two plexuses.
Divisions
First lumbar nerve
The first lumbar spinal nerve (L1) originates from the spinal column from below the
lumbar vertebra 1 (L1). The three terminal branches of this nerve are the
iliohypogastric,
ilioinguinal, and the
genitofemoral nerves
The genitofemoral nerve is a mixed branch of the lumbar plexus derived from anterior rami of lumbar nerves L1–L2. It splits into a genital branch and a femoral branch. It provides sensory innervation to the upper anterior thigh, as well as ...
.
L1 supplies many muscles, either directly or through nerves originating from L1. They may be innervated with L1 as single origin, or be innervated partly by L1 and partly by other spinal nerves. The muscles are:
*
quadratus lumborum (partly)
*
iliopsoas muscle
The iliopsoas muscle (; ) refers to the joined psoas major muscle, psoas major and the iliacus muscles. The two muscles are separate in the abdomen, but usually merge in the thigh. They are usually given the common name ''iliopsoas''. The iliopso ...
(partly)
Second lumbar nerve
The second lumbar spinal nerve (L2) originates from the spinal column from below the
lumbar vertebra 2 (L2).
L2 supplies many muscles, either directly or through nerves originating from L2. They may be innervated with L2 as single origin, or be innervated partly by L2 and partly by other spinal nerves. The muscles are:
*
quadratus lumborum (partly)
*
iliopsoas
The iliopsoas muscle (; ) refers to the joined psoas major and the iliacus muscles. The two muscles are separate in the abdomen, but usually merge in the thigh. They are usually given the common name ''iliopsoas''. The iliopsoas muscle joins t ...
(partly)
Third lumbar nerve
The third lumbar spinal nerve (L3) originates from the spinal column from below the
lumbar vertebra 3 (L3).
L3 supplies many muscles, either directly or through nerves originating from L3. They may be innervated with L3 as single origin, or be innervated partly by L3 and partly by other spinal nerves. The muscles are:
*
quadratus lumborum (partly)
*
iliopsoas
The iliopsoas muscle (; ) refers to the joined psoas major and the iliacus muscles. The two muscles are separate in the abdomen, but usually merge in the thigh. They are usually given the common name ''iliopsoas''. The iliopsoas muscle joins t ...
(partly)
*
obturator externus
The external obturator muscle or obturator externus muscle (; OE) is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis.
It is sometimes considered part of the medial compartment of thigh, and sometime ...
(partly)
Fourth lumbar nerve
The fourth lumbar spinal nerve (L4) originates from the spinal column from below the
lumbar vertebra 4 (L4).
L4 supplies many muscles, either directly or through nerves originating from L4. They are not innervated with L4 as single origin, but partly by L4 and partly by other spinal nerves. The muscles are:
*
quadratus lumborum
*
gluteus medius muscle
*
gluteus minimus muscle
*
tensor fasciae latae
*
obturator externus
The external obturator muscle or obturator externus muscle (; OE) is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis.
It is sometimes considered part of the medial compartment of thigh, and sometime ...
*
inferior gemellus
*
quadratus femoris
*
tibialis anterior
The tibialis anterior muscle is a muscle of the anterior compartment of the lower leg. It originates from the upper portion of the tibia; it inserts into the medial cuneiform and first metatarsal bones of the foot. It acts to dorsiflex and invert ...
*
vastus lateralis
The vastus lateralis (), also called the vastus externus, is the largest and most powerful part of the quadriceps femoris, a muscle in the thigh. Together with other muscles of the quadriceps group, it serves to extend the knee joint, moving the ...
Fifth lumbar nerve
The fifth lumbar spinal nerve 5 (L5)
American Medical Association
Nervous System -- Groups of Nerves originates from the spinal column from below the lumbar vertebra 5 (L5).
L5 supplies many muscles, either directly or through nerves originating from L5. They are not innervated with L5 as single origin, but partly by L5 and partly by other spinal nerves. The muscles are:
* gluteus maximus muscle mainly S1
* gluteus medius muscle
* gluteus minimus muscle
* tensor fasciae latae
* tibialis anterior
The tibialis anterior muscle is a muscle of the anterior compartment of the lower leg. It originates from the upper portion of the tibia; it inserts into the medial cuneiform and first metatarsal bones of the foot. It acts to dorsiflex and invert ...
* tibialis posterior
* extensor digitorum brevis
The extensor digitorum brevis muscle (sometimes EDB) is a muscle on the upper surface of the foot that helps extend digits 2 through 4.
Structure
The muscle originates from the forepart of the upper and lateral surface of the calcaneus (in front ...
* extensor hallucis longus
File:Slide1w.JPG, Lumbar spinal nerve 3
File:Slide2w.JPG, Lumbar spinal nerve 4
File:CORECTAT.jpg, Lumbar spinal nerve 5
Sobo 1909 612.png, The spinal cord with spinal nerves
Sobo 1909 715.png, The plan of the lumbosacral plexus
Function
Additional images
File:Gray823.png, The lumbar plexus and its branches.
File:Slide4ARS.JPG, Lumbar spinal nerves.Deep dissection. Posterior view.
See also
* Lumbar plexus
The lumbar plexus is a web of nerves (a nerve plexus) in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1–L4) and from contributions of the su ...
References
Hsu, Philip S., MD, Carmel Armon, MD, and Kerry Levin, MD. "Acute Lumbosacral Radiculopathy: Pathophysiology.Clinical, Features, and Diagnosis." www.uptodate.com. Uptodate, 11 Jan. 2011.Web. 26 Sept. 2012. https://www.uptodate.com/contents/acute-lumbosacral-radiculopathy-pathophysiology-clinical-features-and-diagnosis
Loizidez, Alexander, MD, Siegfried Peer, MD, Michaela Plaikner, MD, Verena Spiss, MD, and HannesGruber, MD. "Ultrasound-guided Injections in the Lumbar Spine." www.medultrason.ro. Medical Ultrasonography, 20 Jan. 2011. Web. 26 Sept. 2012. http://www.medultrason.ro/assets/Magazines/Medultrason-2011-vol13-no1/10loizides.pdf
Zhu, Jie, MD, and Obi Onyewu, MD. "Alternative Approach for Lumbar Transforaminal Epidural Steroid Injections." www.painphysicianjournal.com. Pain Physician, 21 Apr. 2011. Web. 26 Sept. 2012. http://www.painphysicianjournal.com/2011/july/2011;14;331-341.pdf
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Spinal nerves