Thelumbar vertebrae are located between thethoracic vertebrae andpelvis. They form the lower part of theback in humans, and the tail end of the back inquadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe the anatomy of humans and quadrupeds, such as horses, pigs, or cattle. These bones are found in particular cuts of meat, including tenderloin or sirloin steak.

Lumbar vertebrae
Position of human lumbar vertebrae (shown in red). It consists of 5 bones, from the top down, L1, L2, L3, L4 and L5.
Animation of L1
Details
Insertions	Psoas major muscle
Nerve	Lumbar nerves
Identifiers
Latin	vertebrae lumbales
MeSH	D008159
TA98	A02.2.04.001
TA2	1068
FMA	9921
Anatomical terms of bone [edit on Wikidata]

In human anatomy, the fivevertebrae are between therib cage and thepelvis. They are the largest segments of thevertebral column and are characterized by the absence of theforamen transversarium within the transverse process (since it is only found in thecervical region) and by the absence of facets on the sides of the body (as found only in thethoracic region). They are designated L1 to L5, starting at the top. The lumbar vertebrae help support the weight of the body, and permit movement.

The adjacent figure depicts the general characteristics of the first through fourth lumbar vertebrae. The fifth vertebra contains certain peculiarities, which are detailed below.

As with other vertebrae, each lumbar vertebra consists of avertebral body and avertebral arch. The vertebral arch, consisting of a pair ofpedicles and a pair oflaminae, encloses thevertebral foramen (opening) and supports sevenprocesses.

Thevertebral body of each lumbar vertebra is kidney shaped, wider from side to side than from front to back, and a little thicker in front than in back. It is flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides.^[1]

Thepedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth.^[1] The pedicles change in morphology from the upper lumbar to the lower lumbar. They increase insagittal width from 9 mm to up to 18 mm at L5. They increase in angulation in the axial plane from 10 degrees to 20 degrees by L5. The pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement ofbone cement as withkyphoplasty or vertebroplasty.

Thelaminae are broad, short, and strong.^[1] They form the posterior portion of the vertebral arch. In the upper lumbar region the lamina are taller than wide, but in the lower lumbar vertebra the lamina are wider than tall. The lamina connects the spinous process to the pedicles.

Thevertebral foramen within the arch is triangular, larger than thethoracic vertebrae, but smaller than in thecervical vertebrae.^[1]

Thespinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.^[1]

The superior and inferiorarticular processes are well-defined, projecting respectively upward and downward from the junctions of pedicles and laminae. The facets on the superior processes are concave, and look backward andmedialward; those on the inferior are convex, and are directed forward and lateralward. The former are wider apart than the latter since in the articulated column, the inferior articular processes are embraced by the superior processes of the subjacent vertebra.^[1]

Thetransverse processes are long and slender. They are horizontal in the upper three lumbar vertebrae and incline a little upward in the lower two. In the upper three vertebrae they arise from the junctions of the pedicles and laminae, but in the lower two they are set further forward and spring from the pedicles and posterior parts of the vertebral bodies. They are situated in front of the articular processes instead of behind them as in the thoracic vertebrae, and arehomologous with the ribs.^[1]

Three portions ortubercles can be noticed in a transverse process of a lower lumbar vertebrae: the lateral orcostiform process, themammillary process, and theaccessory process.^[2] The costiform is lateral, the mammillary is superior (cranial), and the accessory is inferior (caudal). The mammillary is connected in the lumbar region with the back part of the superior articular process.^{[clarification needed]} The accessory process is situated at the back part of the base of the transverse process. The tallest and thickest costiform process is usually that of L5.^[2]

The first lumbar vertebra is level with the anterior end of theninth rib. This level is also called the importanttranspyloric plane, since thepylorus of the stomach is at this level. Other important structures are also located at this level. They include fundus of the gall bladder, celiac trunk, superior mesenteric artery, termination of spinal cord, beginning offilum terminale, renal vessels, middle suprarenal arteries, andhila of kidneys.

The fifth lumbar vertebra is characterized by its body being much deeper in front than behind, which accords with the prominence of the sacrovertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articular processes, and by the thickness of its transverse processes, which spring from the body as well as from the pedicles.^[1]The fifth lumbar vertebra is by far the most common site ofspondylolysis andspondylolisthesis.^[3]

Most individuals have five lumbar vertebrae, while some have four or six. Lumbar disorders that normally affect L5 will affect L4 or L6 in these latter individuals.

The range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but also because it is age and sex dependent. Furthermore, flexion and extension in the lumbal spine is the product of a combination of rotation and translation in the sagittal plane between each vertebra.^[4]

Ranges of segmental movements in the lumbar spine (White and Punjabi, 1990) are (in degrees):^[5]

Congenital vertebral anomalies can cause compression of thespinal cord by deforming the vertebral canal or causing instability.

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  Lumbarization ofsacral vertebra 1, seen as 6 vertebrae that do not connect toribs.
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  Sacralization of the L5 vertebra is seen at the lower right of the image.
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  Congenital block vertebra of the lumbar spine. CT volume rendering.

African apes have three and four lumbar vertebrae, (bonobos have longer spines with an additional vertebra) and humans normally five. This difference, and because the lumbar spines of the extinctNacholapithecus (aMiocene hominoid with six lumbar vertebrae and no tail) are similar to those of earlyAustralopithecus and earlyHomo, it is assumed that thechimpanzee–human last common ancestor also had a long vertebral column with a long lumbar region and the reduction in the number of lumbar vertebrae evolved independently in each apeclade.^[6]The limited number of lumbar vertebrae inchimpanzees andgorillas result in an inability tolordose (curve) their lumbar spines, in contrast to the spines ofOld World monkeys andNacholapithecus andProconsul, which suggests that the last common ancestor was not "short-backed" as previously believed.^[7]

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  MRI lumbar spine with degeneration (sagittal T2 FRFSE)
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  MRI lumbar spine with degeneration (sagittal T1 FSE)
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  MRI lumbar spine with degeneration (sagittal FAST STIR)
• MRI lumbar spine pre-hemilaminectomy (sagittal T2 FRFSE)
• MRI lumbar spine pre-hemilaminectomy (sagittal T1 FSE)
• MRI lumbar spine pre-hemilaminectomy (sagittal FAST STIR)
• MRI lumbar spine post-hemilaminectomy (sagittal T2 FRFSE)
• MRI lumbar spine post-hemilaminectomy (sagittal T1 FSE)
• Contrast MRI lumbar spine post-hemilaminectomy (sagittal T1 FSE FS)

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  3D image of a lumbar vertebra
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  Position of lumbar vertebrae (shown in red). Animation.
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  Same as the left. Bones around the lumbar vertebrae are shown as semi-transparent.
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  Shape of lumbar vertebrae (shown in blue and yellow). Animation.
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  Vertebral column.
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  Muscles of the iliac and anterior femoral regions. First lumbar vertebra second highest vertebra seen.
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  Orientation of vertebral column on surface. T3 is at level of medial part ofspine of scapula. T7 is atinferior angle of the scapula. L4 is at highest point ofiliac crest. S2 is at the level ofposterior superior iliac spine. Furthermore, C7 is easily localized as a prominence at the lower part of the neck.^[8]
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  Vertebral column
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  Illustration highlighting lumbar spine.
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  A lumbar vertebra seen from the side
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  Ossification of lumbar vertebrae

• Bertolotti's syndrome
• Spinal disc herniation
• Lumbar spinal stenosis
• Degenerative disc disease

 This article incorporates text in thepublic domain frompage 104 of the 20th edition ofGray's Anatomy(1918)

• "Lower Back Pain Condition, Treatment and Exercise". SpineUniverse. RetrievedFebruary 15, 2017.
• "Virtual Spine — Online Learning Resource". Toronto Western Hospital Department of Anesthesia and Pain Management. RetrievedFebruary 15, 2017.