Lumbar vertebrae

In human anatomy, the five lumbar vertebrae are between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse process (since it is only found in the cervical region) and by the absence of facets on the sides of the body (as found only in the thoracic region). They are designated L1 to L5, starting at the top. The lumbar vertebrae help support the weight of the body, and permit movement. General characteristics 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 a vertebral body and a vertebral arch. The vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven processes. Body The vertebral 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. Arch The pedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth. 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. 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. 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. Segmental movements 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. Ranges of segmental movements in the lumbar spine are (in degrees): Congenital anomalies Congenital vertebral anomalies can cause compression of the spinal cord by deforming the vertebral canal or causing instability. File:Lumbarization of S1.jpg|Lumbarization of sacral vertebra 1, seen as 6 vertebrae that do not connect to ribs. File:Sacralization of the fifth lumbar vertebra.jpg|Sacralization of the L5 vertebra is seen at the lower right of the image. File:Blockwirbel CT VR frontal.jpg|Congenital block vertebra of the lumbar spine. CT volume rendering. ==Other apes==

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 extinct Nacholapithecus (a Miocene hominoid with six lumbar vertebrae and no tail) are similar to those of early Australopithecus and early Homo, it is assumed that the chimpanzee–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 ape clade. The limited number of lumbar vertebrae in chimpanzees and gorillas result in an inability to lordose (curve) their lumbar spines, in contrast to the spines of Old World monkeys and Nacholapithecus and Proconsul, which suggests that the last common ancestor was not "short-backed" as previously believed. == Additional images ==

MRI File:SAGITTAL-FRFSE-T2 MRI.jpg|MRI lumbar spine with degeneration (sagittal T2 FRFSE) File:SAGITTAL-FSE T1 MRI.jpg|MRI lumbar spine with degeneration (sagittal T1 FSE) File:SAGITTAL-FAST-STIR-MRI.jpg|MRI lumbar spine with degeneration (sagittal FAST STIR) File:SAGITTAL-FRFSE-T2 MRI.ogg|MRI lumbar spine pre-hemilaminectomy (sagittal T2 FRFSE) File:SAGITTAL-FSE T1 MRI.ogg|MRI lumbar spine pre-hemilaminectomy (sagittal T1 FSE) File:SAGITTAL-FAST-STIR MRI.ogg|MRI lumbar spine pre-hemilaminectomy (sagittal FAST STIR) File:SAG.-T2-FRFSE-L-SPINE.ogg|MRI lumbar spine post-hemilaminectomy (sagittal T2 FRFSE) File:SAG.-T1-FSE-L-SPINE.ogg|MRI lumbar spine post-hemilaminectomy (sagittal T1 FSE) File:SAG.-T1-FSE-FS-L-SPINE-C+.ogg|Contrast MRI lumbar spine post-hemilaminectomy (sagittal T1 FSE FS) Illustrations File:Human lumbar vertebra.stl|3D image of a lumbar vertebra File:Lumbar vertebrae animation.gif|Position of lumbar vertebrae (shown in red). Animation. File:Lumbar vertebrae animation4.gif|Same as the left. Bones around the lumbar vertebrae are shown as semi-transparent. File:Lumbar vertebrae - close-up - animation2.gif|Shape of lumbar vertebrae (shown in blue and yellow). Animation. File:Gray_111_-_Vertebral_column-coloured.png|Vertebral column. File:Gray430.png|Muscles of the iliac and anterior femoral regions. First lumbar vertebra second highest vertebra seen. File:Orientation.PNG|Orientation of vertebral column on surface. T3 is at level of medial part of spine of scapula. T7 is at inferior angle of the scapula. L4 is at highest point of iliac crest. S2 is at the level of posterior superior iliac spine. Furthermore, C7 is easily localized as a prominence at the lower part of the neck. File:Illu vertebral column.svg|Vertebral column File:Blausen 0618 LumbarSpine.png|Illustration highlighting lumbar spine. File:Gray92.png|A lumbar vertebra seen from the side File:Gray106.png|Ossification of lumbar vertebrae == See also ==