NationMaster - Encyclopedia: Lumbar vertebrae

The lumbar vertebrae are the largest segments of the movable part of the vertebral column, and are characterized by the absence of the foramen transversarium within the transverse process, and by the absence of facets on the sides of the body. Image File history File links No higher resolution available. ... Image File history File links Illu_vertebral_column. ... The vertebral column seen from the side Different regions (curvatures) of the vertebral column The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ... The transverse processes of the cervical vertebrae are each pierced by the foramen transversarium, which, in the upper six vertebrÃ¦, gives passage to the vertebral artery and vein and a plexus of sympathetic nerves. ...

General characteristics

These are the general characteristics of the first through fourth lumbar vertebrae. The fifth vertebra contain 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. In anatomy, a process (Latin: processus) is a projection or outgrowth of tissue from a larger body. ...

Vertebral body

The vertebral body of each lumbar vertebra is large, 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. A diagram of a thoracic vertebra. ...

Vertebral 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 pedicles change in morphology from the upper lumbar to the lower lumbar. They increase in sagittal 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 of bone cement as with kyphoplasty or vertebroplasty. In anatomy, the pedicle (also spelled pedicel) is the segment between the transverse process and the vertebral body. ... This article or section does not cite its references or sources. ... Kyphoplasty is a medical procedure where the original height and angle of kyphosis of a fractured vertebra (of certain types) are restored, followed by its stabilization using injected bone filler material. ...

The laminae are broad, short, and strong. 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 connect the spinous process to the pedicles.

The vertebral foramen within the arch is triangular, larger than in the thoracic vertebrae, but smaller than in the cervical vertebrae. In anatomy, a foramen is any opening. ... A typical thoracic vertebra The thoracic vertebrae (vertebrae thoracales) compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. ... In vertebrates, cervical vertebrae (singular: vertebra) are those vertebrae immediately behind (caudal to) the skull. ...

Processes

The spinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.

The superior and inferior articular 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 and medialward; 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. In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. ...

The transverse 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 farther 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 are homologous with the ribs. In biology, homology is any similarity between structures that is due to their shared ancestry. ...

Of the three tubercles noticed in connection with the transverse processes of the lower thoracic vertebrae, the superior one is connected in the lumbar region with the back part of the superior articular process, and is named the mammillary process. The inferior is situated at the back part of the base of the transverse process, and is called the accessory process.

Peculiar lumbar vertebrae

Some individuals have four lumbar vertebrae, while others have six. Lumbar disorders that normally affect L5 will affect L4 or L6 in these individuals. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...

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.

The fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis. Spondylolysis is a defect in the pars interarticularis of a vertebra. ... Spondylolisthesis (not to be confused with spondylosis or spondylolysis), also known as hangmans fracture, is an anteroposterior translatory movement (displacement) of two spinal vertebrae in relationship to each other caused by instability between the two involved vertebrae. ...

Additional images

See Also

Bertolottis syndrome is a form of lumbago in the lumbosacral transitional vertebrae. ...

External links

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant. The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ... An illustration from the 1918 edition Henry Grays Anatomy of the Human Body (or Grays Anatomy as it has more commonly become known) is an anatomy textbook widely regarded as a classic work on human anatomy. ...

Categories: Lower back | Skeletal system This article is about the skeletal organs. ... The human torso Torso is an anatomical term for the greater part of the human body without the head and limbs. ... The sternum (from Greek ÏƒÏ„ÎÏÎ½Î¿Î½, sternon, chest) or breastbone is a long, flat bone located in the center of the thorax (chest). ... This article needs to be cleaned up to conform to a higher standard of quality. ... Sternum or breastbone is a long, flat bone located in the center of the thorax (chest). ... The sternal angle is the angle formed by the junction of the manubrium and the body of the sternum. ... The body of the sternum (gladiolus), considerably lengthier, narrower, and thinner than the manubrium, attains its greatest breadth close to the lower end. ... The xiphisternal joint (or xiphisternal synchondrosis) is a location near the bottom of the sternum, where the following two parts of the sternum meet: body of the sternum xiphoid process It is in line with the T9 vertebrae. ... The xiphoid process is a small cartilaginous extension to the lower part of the sternum which is usually ossified in the adult human. ... The human rib cage. ... The first rib is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward. ... The second rib is much longer than the first, but has a very similar curvature. ... The tenth rib has only a single articular facet on its head. ... The eleventh rib has a single articular facet on the head, which is of rather large size. ... The twelfth rib has a single articular facet on the head, which is of rather large size. ... Excluding the first seven ribs, the remaining five are false ribs. ... the four floating ribs Four of the ribs (two pairs) in the ribcage are said to be floating ribs because they are attached to the vertebrae only, and not to the sternum or cartilage coming off of the sternum. ... The external surface of the rib is convex, smooth, and marked, a little in front of the tubercle, by a prominent line, directed downward and laterally; this gives attachment to a tendon of the Iliocostalis, and is called the angle. ... On the posterior surface at the junction of the neck and body of the rib, and nearer the lower than the upper border, is an eminenceâ€”the tubercle It consists of an articular and a non-articular portion. ... Between the ridge of the interal surface of the rib and the inferior border is a groove, the costal groove, for the intercostal vessels and intercostal nerve. ... The neck of the rib is the flattened portion which extends lateralward from the head; it is about 2. ... The head of the rib is marked by a kidney-shaped articular surface, divided by a horizontal crest into two facets for articulation with the depression formed on the bodies of two adjacent thoracic vertebrae; the upper facet is the smaller; to the crest is attached the interarticular ligament. ... The body is the largest part of a vertebra, and is more or less cylindrical in shape. ... The vertebral arch (or neural arch) is the posterior part of a vertebra. ... The pedicles are two short, thick processes, which project backward, one on either side, from the upper part of the body, at the junction of its posterior and lateral surfaces. ... The laminÃ¦ are two broad plates directed backward and medialward from the pedicles. ... The concavities above and below the pedicles are named the vertebral notches; and when the vertebrae are articulated, the notches of each contiguous pair of bones form the intervertebral foramina. ... In a typical vertebra, the vertebral foramen is the foramen formed by the anterior segment (the body), and the posterior part, the vertebral arch. ... When the spinal vertebrae are articulated with each other the bodies form a strong pillar for the support of the head and trunk, and the vertebral foraminae constitute a canal for the protection of the medulla spinalis (spinal cord). ... The transverse processes of a vertebra, two in number, project one at either side from the point where the lamina joins the pedicle, between the superior and inferior articular processes. ... The articular processes of a vertebra, two superior and two inferior, spring from the junctions of the pedicles and laminÃ¦. The superior project upward, and their articular surfaces are directed more or less backward; the inferior project downward, and their surfaces look more or less forward. ... A zygapophysis is process which sticks out of an end of a vertebra to lock with a zygapophysis on the next vertebra, to make the backbone more stable. ... A diagram of a thoracic vertebra. ... In vertebrates, cervical vertebrae (singular: vertebra) are those vertebrae immediately behind (caudal to) the skull. ... In anatomy, the atlas (C1) is the topmost (first) cervical vertebra of the spine. ... The anterior arch of the atlas forms about one-fifth of the ring of the atlas: its anterior surface is convex, and presents at its center the anterior tubercle for the attachment of the Longus colli muscles; posteriorly it is concave, and marked by a smooth, oval or circular facet... In a cervical vertebra, the posterior arch forms about two-fifths of the circumference of the ring: it ends behind in the posterior tubercle, which is the rudiment of a spinous process and gives origin to the Recti capitis posteriores minores. ... The lateral masses are the most bulky and solid parts of the atlas, in order to support the weight of the head. ... In anatomy, the second cervical vertebra (C2) of the spine is named the axis or epistropheus. ... The dens or odontoid process or odontoid peg of the axis exhibits a slight constriction or neck, where it joins the body. ... The most distinctive characteristic of the seventh cervical vertebra is the existence of a long and prominent spinous process, hence the name vertebra prominens. ... The anterior arch forms about one-fifth of the ring: its anterior surface is convex, and presents at its center the anterior tubercle for the attachment of the Longus colli muscles. ... The posterior arch of a cervical vertebra forms about two-fifths of the circumference of the ring: it ends behind in the posterior tubercle, which is the rudiment of a spinous process and gives origin to the Recti capitis posteriores minores. ... The transverse processes of the cervical vertebrae are each pierced by the foramen transversarium, which, in the upper six vertebrÃ¦, gives passage to the vertebral artery and vein and a plexus of sympathetic nerves. ... A typical thoracic vertebra The thoracic vertebrae (vertebrae thoracales) compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. ... The superior costal facet (or superior costal fovea) is a site where a rib forms a joint with the top of a vertebra. ... The inferior costal facet (or inferior costal fovea) is a site where a rib forms a joint with the bottom of a vertebra. ... The transverse costal facet (or transverse costal fovea) is a site where a rib forms a joint with the transverse process of a vertebra. ... Of the tubercles noticed in connection with the transverse processes of the lower thoracic vertebrae, the inferior is situated at the back part of the base of the transverse process, and is called the accessory process. ... Of the three tubercles noticed in connection with the transverse processes of the lower thoracic vertebrae, the superior one is connected in the lumbar region with the back part of the superior articular process, and is named the mammillary process. ... For the record label, see Sacrum Torch. ... The coccyx is formed of up to five vertebrae. ... The pelvic surface of sacrum is concave from above downward, and slightly so from side to side. ... At the ends of the transverse ridges of the pelvic surface of the sacrum are seen the anterior sacral foramina (or pelvic sacral foramina), four in number on either side, somewhat rounded in form, diminishing in size from above downward, and directed lateralward and forward; they give exit to the... The dorsal surface of sacrum is convex and narrower than the pelvic. ... Lateral to the articular processes of the sacrum are the four posterior sacral foramina (or dorsal sacral foramina); they are smaller in size and less regular in form than the anterior, and transmit the posterior divisions of the sacral nerves. ... In the middle line of the dorsal surface of the sacrum, it displays a crest, the median sacral crest, surmounted by three or four tubercles, the rudimentary spinous processes of the upper three or four sacral vertebrae. ... On the lateral aspect of the sacral groove is a linear series of tubercles produced by the fusion of the articular processes which together form the indistinct medial sacral crest (intermediate sacral crest, sacral articular crest). ... On the lateral side of the posterior sacral foramina is a series of tubercles, which represent the transverse processes of the sacral vertebrae, and form the lateral sacral crest. ... The lateral surface of sacrum is broad above, but narrowed into a thin edge below. ... The base of the sacrum, which is broad and expanded, is directed upward and forward. ... The laminae of the fifth sacral vertebra, and sometimes those of the fourth, fail to meet behind, and thus a sacral hiatus or deficiency occurs in the posterior wall of the sacral canal. ... In human anatomy, the presacral space is behind the rectum and in front of the coccyx. ... The Sacral promontory is the anatomical term for the anteriormost portion of the sacrum. ...

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