Vertebra

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For other uses, see Vertebra (disambiguation). Vertebra_sentence_0

Vertebra_table_infobox_0

VertebraVertebra_header_cell_0_0_0
DetailsVertebra_header_cell_0_1_0
Part ofVertebra_header_cell_0_2_0 Spinal columnVertebra_cell_0_2_1
IdentifiersVertebra_header_cell_0_3_0
LatinVertebra_header_cell_0_4_0 VertebraeVertebra_cell_0_4_1
TA98Vertebra_header_cell_0_5_0 Vertebra_cell_0_5_1
TA2Vertebra_header_cell_0_6_0 Vertebra_cell_0_6_1
FMAVertebra_header_cell_0_7_0 Vertebra_cell_0_7_1

In the vertebrate spinal column, each vertebra is an irregular bone with a complex structure composed of bone and some hyaline cartilage, the proportions of which vary according to the segment of the backbone and the species of vertebrate. Vertebra_sentence_1

The basic configuration of a vertebra varies; the large part is the body, and the central part is the centrum. Vertebra_sentence_2

The upper and lower surfaces of the vertebra body give attachment to the intervertebral discs. Vertebra_sentence_3

The posterior part of a vertebra forms a vertebral arch, in eleven parts, consisting of two pedicles, two laminae, and seven processes. Vertebra_sentence_4

The laminae give attachment to the ligamenta flava (ligaments of the spine). Vertebra_sentence_5

There are vertebral notches formed from the shape of the pedicles, which form the intervertebral foramina when the vertebrae articulate. Vertebra_sentence_6

These foramina are the entry and exit conduits for the spinal nerves. Vertebra_sentence_7

The body of the vertebra and the vertebral arch form the vertebral foramen, the larger, central opening that accommodates the spinal canal, which encloses and protects the spinal cord. Vertebra_sentence_8

Vertebrae articulate with each other to give strength and flexibility to the spinal column, and the shape at their back and front aspects determines the range of movement. Vertebra_sentence_9

Structurally, vertebrae are essentially alike across the vertebrate species, with the greatest difference seen between an aquatic animal and other vertebrate animals. Vertebra_sentence_10

As such, vertebrates take their name from the vertebrae that compose the vertebral column. Vertebra_sentence_11

Structure Vertebra_section_0

General structure Vertebra_section_1

In the human vertebral column the size of the vertebrae varies according to placement in the vertebral column, spinal loading, posture and pathology. Vertebra_sentence_12

Along the length of the spine the vertebrae change to accommodate different needs related to stress and mobility. Vertebra_sentence_13

Each vertebra is an irregular bone. Vertebra_sentence_14

Every vertebra has a body, which consists of a large anterior middle portion called the centrum (plural centra) and a posterior vertebral arch, also called a neural arch. Vertebra_sentence_15

The body is composed of cancellous bone, which is the spongy type of osseous tissue, whose micro-anatomy has been specifically studied within the pedicle bones. Vertebra_sentence_16

This cancellous bone is in turn, covered by a thin coating of cortical bone (or compact bone), the hard and dense type of osseous tissue. Vertebra_sentence_17

The vertebral arch and processes have thicker coverings of cortical bone. Vertebra_sentence_18

The upper and lower surfaces of the body of the vertebra are flattened and rough in order to give attachment to the intervertebral discs. Vertebra_sentence_19

These surfaces are the vertebral endplates which are in direct contact with the intervertebral discs and form the joint. Vertebra_sentence_20

The endplates are formed from a thickened layer of the cancellous bone of the vertebral body, the top layer being more dense. Vertebra_sentence_21

The endplates function to contain the adjacent discs, to evenly spread the applied loads, and to provide anchorage for the collagen fibers of the disc. Vertebra_sentence_22

They also act as a semi-permeable interface for the exchange of water and solutes. Vertebra_sentence_23

The vertebral arch is formed by pedicles and laminae. Vertebra_sentence_24

Two pedicles extend from the sides of the vertebral body to join the body to the arch. Vertebra_sentence_25

The pedicles are short thick processes that extend, one from each side, posteriorly, from the junctions of the posteriolateral surfaces of the centrum, on its upper surface. Vertebra_sentence_26

From each pedicle a broad plate, a lamina, projects backwards and medialwards to join and complete the vertebral arch and form the posterior border of the vertebral foramen, which completes the triangle of the vertebral foramen. Vertebra_sentence_27

The upper surfaces of the laminae are rough to give attachment to the ligamenta flava. Vertebra_sentence_28

These ligaments connect the laminae of adjacent vertebra along the length of the spine from the level of the second cervical vertebra. Vertebra_sentence_29

Above and below the pedicles are shallow depressions called vertebral notches (superior and inferior). Vertebra_sentence_30

When the vertebrae articulate the notches align with those on adjacent vertebrae and these form the openings of the intervertebral foramina. Vertebra_sentence_31

The foramina allow the entry and exit of the spinal nerves from each vertebra, together with associated blood vessels. Vertebra_sentence_32

The articulating vertebrae provide a strong pillar of support for the body. Vertebra_sentence_33

Processes Vertebra_section_2

There are seven processes projecting from the vertebra: Vertebra_sentence_34

Vertebra_unordered_list_0

  • one spinous processVertebra_item_0_0
  • two transverse processesVertebra_item_0_1
  • four articular processesVertebra_item_0_2

A major part of a vertebra is a backward extending spinous process (sometimes called the neural spine) which projects centrally. Vertebra_sentence_35

This process points dorsally and caudally from the junction of the laminae. Vertebra_sentence_36

The spinous process serves to attach muscles and ligaments. Vertebra_sentence_37

The two transverse processes, one on each side of the vertebral body, project laterally from either side at the point where the lamina joins the pedicle, between the superior and inferior articular processes. Vertebra_sentence_38

They also serve for the attachment of muscles and ligaments, in particular the intertransverse ligaments. Vertebra_sentence_39

There is a facet on each of the transverse processes of thoracic vertebrae which articulates with the tubercle of the rib. Vertebra_sentence_40

A facet on each side of the thoracic vertebral body articulates with the head of the rib. Vertebra_sentence_41

The transverse process of a lumbar vertebra is also sometimes called the costal or costiform process because it corresponds to a rudimentary rib (costa) which, as opposed to the thorax, is not developed in the lumbar region. Vertebra_sentence_42

There are superior and inferior articular facet joints on each side of the vertebra, which serve to restrict the range of movement possible. Vertebra_sentence_43

These facets are joined by a thin portion of the vertebral arch called the pars interarticularis. Vertebra_sentence_44

Regional variation Vertebra_section_3

Vertebrae take their names from the regions of the vertebral column that they occupy. Vertebra_sentence_45

There are thirty-three vertebrae in the human vertebral column—seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, five fused sacral vertebrae forming the sacrum and three to five coccygeal vertebrae, forming the coccyx. Vertebra_sentence_46

The regional vertebrae increase in size as they progress downwards but become smaller in the coccyx. Vertebra_sentence_47

Cervical vertebrae Vertebra_section_4

Main article: Cervical vertebrae Vertebra_sentence_48

There are seven cervical vertebrae (but eight cervical spinal nerves), designated C1 through C7. Vertebra_sentence_49

These bones are, in general, small and delicate. Vertebra_sentence_50

Their spinous processes are short (with the exception of C2 and C7, which have palpable spinous processes). Vertebra_sentence_51

C1 is also called the atlas, and C2 is also called the axis. Vertebra_sentence_52

The structure of these vertebrae is the reason why the neck and head have a large range of motion. Vertebra_sentence_53

The atlanto-occipital joint allows the skull to move up and down, while the atlanto-axial joint allows the upper neck to twist left and right. Vertebra_sentence_54

The axis also sits upon the first intervertebral disc of the spinal column. Vertebra_sentence_55

Cervical vertebrae possess transverse foramina to allow for the vertebral arteries to pass through on their way to the foramen magnum to end in the circle of Willis. Vertebra_sentence_56

These are the smallest, lightest vertebrae and the vertebral foramina are triangular in shape. Vertebra_sentence_57

The spinous processes are short and often (the spinous process of C7, however, is not bifurcated, and is substantially longer than that of the other cervical spinous processes). Vertebra_sentence_58

The atlas differs from the other vertebrae in that it has no body and no spinous process. Vertebra_sentence_59

It has instead a ring-like form, having an anterior and a posterior arch and two lateral masses. Vertebra_sentence_60

At the outside centre points of both arches there is a tubercle, an anterior tubercle and a posterior tubercle, for the attachment of muscles. Vertebra_sentence_61

The front surface of the anterior arch is convex and its anterior tubercle gives attachment to the longus colli muscle. Vertebra_sentence_62

The posterior tubercle is a rudimentary spinous process and gives attachment to the rectus capitis posterior minor muscle. Vertebra_sentence_63

The spinous process is small so as not to interfere with the movement between the atlas and the skull. Vertebra_sentence_64

On the under surface is a facet for articulation with the dens of the axis. Vertebra_sentence_65

Specific to the cervical vertebra is the transverse foramen (also known as foramen transversarium). Vertebra_sentence_66

This is an opening on each of the transverse processes which gives passage to the vertebral artery and vein and a sympathetic nerve plexus. Vertebra_sentence_67

On the cervical vertebrae other than the atlas, the anterior and posterior tubercles are on either side of the transverse foramen on each transverse process. Vertebra_sentence_68

The anterior tubercle on the sixth cervical vertebra is called the carotid tubercle because it separates the carotid artery from the vertebral artery. Vertebra_sentence_69

There is a hook-shaped uncinate process on the side edges of the top surface of the bodies of the third to the seventh cervical vertebrae and of the first thoracic vertebra. Vertebra_sentence_70

Together with the vertebral disc, this uncinate process prevents a vertebra from sliding backwards off the vertebra below it and limits lateral flexion (side-bending). Vertebra_sentence_71

Luschka's joints involve the vertebral uncinate processes. Vertebra_sentence_72

The spinous process on C7 is distinctively long and gives the name vertebra prominens to this vertebra. Vertebra_sentence_73

Also a cervical rib can develop from C7 as an anatomical variation. Vertebra_sentence_74

The term cervicothoracic is often used to refer to the cervical and thoracic vertebrae together, and sometimes also their surrounding areas. Vertebra_sentence_75

Thoracic vertebrae Vertebra_section_5

Main article: Thoracic vertebrae Vertebra_sentence_76

The twelve thoracic vertebrae and their transverse processes have surfaces that articulate with the ribs. Vertebra_sentence_77

Some rotation can occur between the thoracic vertebrae, but their connection with the rib cage prevents much flexion or other movement. Vertebra_sentence_78

They may also be known as "dorsal vertebrae" in the human context. Vertebra_sentence_79

The vertebral bodies are roughly heart-shaped and are about as wide anterio-posteriorly as they are in the transverse dimension. Vertebra_sentence_80

Vertebral foramina are roughly circular in shape. Vertebra_sentence_81

The top surface of the first thoracic vertebra has a hook-shaped uncinate process, just like the cervical vertebrae. Vertebra_sentence_82

The thoracolumbar division refers to the thoracic and lumbar vertebrae together, and sometimes also their surrounding areas. Vertebra_sentence_83

The thoracic vertebrae attach to ribs and so have articular facets specific to them; these are the superior, transverse and inferior costal facets. Vertebra_sentence_84

As the vertebrae progress down the spine they increase in size to match up with the adjoining lumbar section. Vertebra_sentence_85

Lumbar vertebrae Vertebra_section_6

Main article: Lumbar vertebrae Vertebra_sentence_86

The five lumbar vertebrae are the largest of the vertebrae, their robust construction being necessary for supporting greater weight than the other vertebrae. Vertebra_sentence_87

They allow significant flexion, extension and moderate lateral flexion (side-bending). Vertebra_sentence_88

The discs between these vertebrae create a natural lumbar lordosis (a spinal curvature that is concave posteriorly). Vertebra_sentence_89

This is due to the difference in thickness between the front and back parts of the intervertebral discs. Vertebra_sentence_90

The lumbar vertebrae are located between the ribcage and the pelvis and are the largest of the vertebrae. Vertebra_sentence_91

The pedicles are strong, as are the laminae, and the spinous process is thick and broad. Vertebra_sentence_92

The vertebral foramen is large and triangular. Vertebra_sentence_93

The transverse processes are long and narrow and three tubercles can be seen on them. Vertebra_sentence_94

These are a lateral cosiform process, a mammillary process and an accessory process. Vertebra_sentence_95

The superior, or upper tubercle is the mammillary process which connects with the superior articular process. Vertebra_sentence_96

The multifidus muscle attaches to the mammillary process and this muscle extends through the length of the vertebral column, giving support. Vertebra_sentence_97

The inferior, or lower tubercle is the accessory process and this is found at the back part of the base of the transverse process. Vertebra_sentence_98

The term lumbosacral is often used to refer to the lumbar and sacral vertebrae together, and sometimes includes their surrounding areas. Vertebra_sentence_99

Sacrum Vertebra_section_7

Main article: Sacrum Vertebra_sentence_100

There are five sacral vertebrae (S1–S5) which are fused in maturity, into one large bone, the sacrum, with no intervertebral discs. Vertebra_sentence_101

The sacrum with the ilium forms a sacroiliac joint on each side of the pelvis, which articulates with the hips. Vertebra_sentence_102

Coccyx Vertebra_section_8

Main article: Coccyx Vertebra_sentence_103

The last three to five coccygeal vertebrae (but usually four) (Co1–Co5) make up the tailbone or coccyx. Vertebra_sentence_104

There are no intervertebral discs. Vertebra_sentence_105

Development Vertebra_section_9

Somites form in the early embryo and some of these develop into sclerotomes. Vertebra_sentence_106

The sclerotomes form the vertebrae as well as the rib cartilage and part of the occipital bone. Vertebra_sentence_107

From their initial location within the somite, the sclerotome cells migrate medially towards the notochord. Vertebra_sentence_108

These cells meet the sclerotome cells from the other side of the paraxial mesoderm. Vertebra_sentence_109

The lower half of one sclerotome fuses with the upper half of the adjacent one to form each vertebral body. Vertebra_sentence_110

From this vertebral body, sclerotome cells move dorsally and surround the developing spinal cord, forming the vertebral arch. Vertebra_sentence_111

Other cells move distally to the costal processes of thoracic vertebrae to form the ribs. Vertebra_sentence_112

Function Vertebra_section_10

Functions of vertebrae include: Vertebra_sentence_113

Vertebra_ordered_list_1

  1. Support of the vertebrae function in the skeletomuscular system by forming the vertebral column to support the bodyVertebra_item_1_3
  2. Protection. Vertebrae contain a vertebral foramen for the passage of the spinal canal and its enclosed spinal cord and covering meninges. They also afford sturdy protection for the spinal cord. The upper and lower surfaces of the centrum are flattened and rough in order to give attachment to the intervertebral discs.Vertebra_item_1_4
  3. Movement. The vertebrae also provide the openings, the intervertebral foramina which allow the entry and exit of the spinal nerves. Similarly to the surfaces of the centrum, the upper and lower surfaces of the fronts of the laminae are flattened and rough to give attachment to the ligamenta flava. Working together in the vertebral column their sections provide controlled movement and flexibility.Vertebra_item_1_5
  4. Feeding of the intervertebral discs through the reflex (hyaline ligament) plate that separates the cancellous bone of the vertebral body from each diskVertebra_item_1_6

Vertebra_unordered_list_2

  • Vertebra_item_2_7
  • Vertebra_item_2_8
  • Vertebra_item_2_9
  • Vertebra_item_2_10

Clinical significance Vertebra_section_11

There are a number of congenital vertebral anomalies, mostly involving variations in the shape or number of vertebrae, and many of which are unproblematic. Vertebra_sentence_114

Others though can cause compression of the spinal cord. Vertebra_sentence_115

Wedge-shaped vertebrae, called hemivertebrae can cause an angle to form in the spine which can result in the spinal curvature diseases of kyphosis, scoliosis and lordosis. Vertebra_sentence_116

Severe cases can cause spinal cord compression. Vertebra_sentence_117

Block vertebrae where some vertebrae have become fused can cause problems. Vertebra_sentence_118

Spina bifida can result from the incomplete formation of the vertebral arch. Vertebra_sentence_119

Spondylolysis is a defect in the pars interarticularis of the vertebral arch. Vertebra_sentence_120

In most cases this occurs in the lowest of the lumbar vertebrae (L5), but may also occur in the other lumbar vertebrae, as well as in the thoracic vertebrae. Vertebra_sentence_121

Spinal disc herniation, more commonly called a slipped disc, is the result of a tear in the outer ring (anulus fibrosus) of the intervertebral disc, which lets some of the soft gel-like material, the nucleus pulposus, bulge out in a hernia. Vertebra_sentence_122

This may be treated by a minimally-invasive endoscopic procedure called Tessys method. Vertebra_sentence_123

A laminectomy is a surgical operation to remove the laminae in order to access the spinal canal. Vertebra_sentence_124

The removal of just part of a lamina is called a laminotomy. Vertebra_sentence_125

A pinched nerve caused by pressure from a disc, vertebra or scar tissue might be remedied by a foraminotomy to broaden the intervertebral foramina and relieve pressure. Vertebra_sentence_126

It can also be caused by a foramina stenosis, a narrowing of the nerve opening, as a result of arthritis. Vertebra_sentence_127

Another condition is spondylolisthesis when one vertebra slips forward onto another. Vertebra_sentence_128

The reverse of this condition is retrolisthesis where one vertebra slips backwards onto another. Vertebra_sentence_129

The vertebral pedicle is often used as a radiographic marker and entry point in vertebroplasty, kyphoplasty, and spinal fusion procedures. Vertebra_sentence_130

The arcuate foramen is a common anatomical variation more frequently seen in females. Vertebra_sentence_131

It is a bony bridge found on the first cervical vertebra, the atlas where it covers the groove for the vertebral artery. Vertebra_sentence_132

Degenerative disc disease is a condition usually associated with ageing in which one or more discs degenerate. Vertebra_sentence_133

This can often be a painfree condition but can also be very painful. Vertebra_sentence_134

Other animals Vertebra_section_12

In other animals the vertebrae take the same regional names except for the coccygeal – in animals with tails the separate vertebrae are usually called the caudal vertebrae. Vertebra_sentence_135

Because of the different types of locomotion and support needed between the aquatic and other vertebrates, the vertebrae between them show the most variation, though basic features are shared. Vertebra_sentence_136

The spinous processes which are backward extending are directed upwards in animals without an erect stance. Vertebra_sentence_137

These processes can be very large in the larger animals since they attach to the muscles and ligaments of the body. Vertebra_sentence_138

In the elephant the vertebrae are connected by tight joints, which limit the backbone's flexibility. Vertebra_sentence_139

Spinous processes are exaggerated in some animals, such as the extinct Dimetrodon and Spinosaurus, where they form a sailback or finback. Vertebra_sentence_140

Vertebrae with saddle-shaped articular surfaces on their bodies, called "heterocoelous", allow vertebrae to flex both vertically and horizontally while preventing twisting motions. Vertebra_sentence_141

Such vertebrae are found in the necks of birds and some turtles. Vertebra_sentence_142

"Procoelous" vertebrae feature a spherical protrusion extending from the caudal end of the centrum of one vertebra that fits into a concave socket on the cranial end of the centrum of an adjacent vertebra. Vertebra_sentence_143

These vertebrae are most often found in reptiles, but are found in some amphibians such as frogs. Vertebra_sentence_144

The vertebrae fit together in a ball-and-socket articulation, in which the convex articular feature of an anterior vertebra acts as the ball to the socket of a caudal vertebra. Vertebra_sentence_145

This type of connection permits a wide range of motion in most directions, while still protecting the underlying nerve cord. Vertebra_sentence_146

The central point of rotation is located at the midline of each centrum, and therefore flexion of the muscle surrounding the vertebral column does not lead to an opening between vertebrae. Vertebra_sentence_147

In many species, though not in mammals, the cervical vertebrae bear ribs. Vertebra_sentence_148

In many groups, such as lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae. Vertebra_sentence_149

The transverse processes of mammals are homologous to the cervical ribs of other amniotes. Vertebra_sentence_150

In the whale the cervical vertebrae are typically fused, an adaptation trading flexibility for stability during swimming. Vertebra_sentence_151

All mammals except manatees and sloths have seven cervical vertebrae, whatever the length of the neck. Vertebra_sentence_152

This includes seemingly unlikely animals such as the giraffe, the camel, and the blue whale, for example. Vertebra_sentence_153

Birds usually have more cervical vertebrae with most having a highly flexible neck consisting of 13–25 vertebrae. Vertebra_sentence_154

In all mammals, the thoracic vertebrae are connected to ribs and their bodies differ from the other regional vertebrae due to the presence of facets. Vertebra_sentence_155

Each vertebra has a facet on each side of the vertebral body, which articulates with the head of a rib. Vertebra_sentence_156

There is also a facet on each of the transverse processes which articulates with the tubercle of a rib. Vertebra_sentence_157

The number of thoracic vertebrae varies considerably across the species. Vertebra_sentence_158

Most marsupials have thirteen, but koalas only have eleven. Vertebra_sentence_159

The norm is twelve to fifteen in mammals, (twelve in the human), though there are from eighteen to twenty in the horse, tapir, rhinoceros and elephant. Vertebra_sentence_160

In certain sloths there is an extreme number of twenty-five and at the other end only nine in the cetacean. Vertebra_sentence_161

There are fewer lumbar vertebrae in chimpanzees and gorillas, which have three in contrast to the five in the genus Homo. Vertebra_sentence_162

This reduction in number gives an inability of the lumbar spine to lordose but gives an anatomy that favours vertical climbing, and hanging ability more suited to feeding locations in high-canopied regions. Vertebra_sentence_163

The bonobo differs by having four lumbar vertebrae. Vertebra_sentence_164

Caudal vertebrae are the bones that make up the tails of vertebrates. Vertebra_sentence_165

They range in number from a few to fifty, depending on the length of the animal's tail. Vertebra_sentence_166

In humans and other tailless primates, they are called the coccygeal vertebrae, number from three to five and are fused into the coccyx. Vertebra_sentence_167

Additional images Vertebra_section_13

Vertebra_unordered_list_3

  • Vertebra_item_3_11
  • Vertebra_item_3_12
  • Vertebra_item_3_13
  • Vertebra_item_3_14

See also Vertebra_section_14

Vertebra_unordered_list_4


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Vertebra.