Vertebra

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Vertebrae
Spinal column
Identifiers
LatinVertebrae
TA98A02.2.01.001
TA21011
FMA9914
Anatomical terms of bone]

The

spinal column, characteristic of each vertebrate species,[vague
] is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic
phylogenetic differences among the vertebrate taxa
.

The basic configuration of a vertebra varies, but the bone is its body, with the central part of the body constituting the centrum. The upper (closer to) and lower (further from), respectively, the cranium and its central nervous system surfaces of the vertebra body support attachment to the intervertebral discs. The posterior part of a vertebra forms a vertebral arch (in eleven parts, consisting of

  • two pedicles (pedicle of vertebral arch)
  • two laminae, and
  • seven processes.

The laminae give attachment to the

articulate. These foramina are the entry and exit conduits accommodating the spinal nerves. The body of the vertebra, and its vertebral arch, form the vertebral foramen, which is the larger, stable and central opening: this accommodates the spinal canal, and encloses and protects the spinal cord
.

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. Structurally, vertebrae are essentially alike across the vertebrate species, with the greatest difference seen between an aquatic animal and other vertebrate animals. As such, vertebrates take their name from the vertebrae that compose the vertebral column.

Structure in humans

General structure

In the human vertebral column the size of the vertebrae varies according to placement in the vertebral column, spinal loading, posture and pathology. Along the length of the spine the vertebrae change to accommodate different needs related to stress and mobility.[2] Each vertebra is an irregular bone.

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

collagen fibers of the disc. They also act as a semi-permeable interface for the exchange of water and solutes.[6]

The vertebral arch is formed by pedicles and laminae. Two pedicles extend from the sides of the vertebral body to join the body to the arch. 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. 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.

intervertebral foramina
. The foramina allow the entry and exit of the spinal nerves from each vertebra, together with associated blood vessels. The articulating vertebrae provide a strong pillar of support for the body.

Processes

There are seven processes projecting from the vertebra:

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

muscles and ligaments
.

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

lumbar vertebra is also sometimes called the costal[10][11] or costiform process[12] because it corresponds to a rudimentary rib (costa) which, as opposed to the thorax, is not developed in the lumbar region.[12][13]

There are superior and inferior articular facet joints on each side of the vertebra, which serve to restrict the range of movement possible. These facets are joined by a thin portion of the vertebral arch called the pars interarticularis.

Regional variation

Vertebrae take their names from the regions of the vertebral column that they occupy. There are thirty-three vertebrae in the human vertebral column—seven

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

Cervical vertebrae

There are seven

skull to move up and down, while the atlanto-axial joint
allows the upper neck to twist left and right. The axis also sits upon the first intervertebral disc of the spinal column.

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. These are the smallest, lightest vertebrae and the vertebral foramina are triangular in shape. The spinous processes are short and often bifurcated (the spinous process of C7, however, is not bifurcated, and is substantially longer than that of the other cervical spinous processes).[14]

The atlas differs from the other vertebrae in that it has no body and no spinous process. It has instead a ring-like form, having an anterior and a posterior arch and two lateral masses. At the outside centre points of both arches there is a tubercle, an anterior tubercle and a posterior tubercle, for the attachment of muscles. The front surface of the anterior arch is convex and its anterior tubercle gives attachment to the

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

Specific to the cervical vertebra is the transverse foramen (also known as foramen transversarium). This is an opening on each of the transverse processes which gives passage to the vertebral artery and vein and a sympathetic nerve plexus. 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. The anterior tubercle on the sixth cervical vertebra is called the carotid tubercle because it separates the carotid artery from the vertebral artery.

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. 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). Luschka's joints involve the vertebral uncinate processes.

The spinous process on C7 is distinctively long and gives the name

vertebra prominens to this vertebra. Also a cervical rib can develop from C7 as an anatomical variation
.

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

Thoracic vertebrae

The twelve thoracic vertebrae and their transverse processes have surfaces that articulate with the ribs. Some rotation can occur between the thoracic vertebrae, but their connection with the rib cage prevents much flexion or other movement. They may also be known as "dorsal vertebrae" in the human context.

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

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

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

The thoracic vertebrae attach to ribs and so have articular facets specific to them; these are the superior, transverse and inferior costal facets. As the vertebrae progress down the spine they increase in size to match up with the adjoining lumbar section.

Lumbar vertebrae

The five lumbar vertebrae are the largest of the vertebrae, their robust construction being necessary for supporting greater weight than the other vertebrae. They allow significant flexion, extension and moderate lateral flexion (side-bending). The discs between these vertebrae create a natural lumbar lordosis (a spinal curvature that is concave posteriorly).[citation needed] This is due to the difference in thickness between the front and back parts of the intervertebral discs.

The lumbar vertebrae are located between the ribcage and the pelvis and are the largest of the vertebrae. The pedicles are strong, as are the laminae, and the spinous process is thick and broad. The vertebral foramen is large and triangular. The transverse processes are long and narrow and three tubercles can be seen on them. These are a lateral costiform process, a mammillary process and an accessory process.[15] The superior, or upper tubercle is the mammillary process which connects with the superior articular process. The multifidus muscle attaches to the mammillary process and this muscle extends through the length of the vertebral column, giving support. The inferior, or lower tubercle is the accessory process and this is found at the back part of the base of the transverse process. The term lumbosacral is often used to refer to the lumbar and sacral vertebrae together, and sometimes includes their surrounding areas.

Sacrum

There are five sacral vertebrae (S1–S5) which are fused in maturity, into one large bone, the

hips
.

Coccyx

The last three to five coccygeal vertebrae (but usually four) (Co1–Co5) make up the tailbone or coccyx. There are no intervertebral discs.

Development

Development of vertebrae

vertebral arch. Other cells move distally to the costal processes of thoracic vertebrae to form the ribs.[17]

Function

Functions of vertebrae include:

  1. Support of the vertebrae function in the skeletomuscular system by forming the vertebral column to support the body
  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.
  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.
  4. Feeding of the intervertebral discs through the reflex (hyaline ligament) plate that separates the cancellous bone of the vertebral body from each disk
  • The spinal cord nested in the vertebral column.

    The spinal cord nested in the vertebral column.

  • Vertebral joint

    Vertebral joint

  • Costovertebral joint

    Costovertebral joint

  • A facet joint between the superior and inferior articular processes (labeled at top and bottom).

    A facet joint between the superior and inferior articular processes (labeled at top and bottom).

Clinical significance

There are a number of

Block vertebrae where some vertebrae have become fused can cause problems. Spina bifida
can result from the incomplete formation of the vertebral arch.

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

minimally-invasive endoscopic procedure called Tessys method
.

A laminectomy is a surgical operation to remove the laminae in order to access the spinal canal.[18] The removal of just part of a lamina is called a laminotomy.

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

Another condition is spondylolisthesis when one vertebra slips forward onto another. The reverse of this condition is retrolisthesis where one vertebra slips backwards onto another.

The vertebral pedicle is often used as a radiographic marker and entry point in

kyphoplasty, and spinal fusion
procedures.

The arcuate foramen is a common anatomical variation more frequently seen in females. It is a bony bridge found on the first cervical vertebra, the atlas where it covers the groove for the vertebral artery.[19]

Degenerative disc disease is a condition usually associated with ageing in which one or more discs degenerate. This can often be a painfree condition but can also be very painful.

Other animals

Regions of vertebrae in the goat

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. 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. The spinous processes which are backward extending are directed upwards in animals without an erect stance. These processes can be very large in the larger animals since they attach to the muscles and ligaments of the body. In the

, where they form a sailback or finback.

Vertebrae with saddle-shaped articular surfaces on their bodies, called "heterocoelous", allow vertebrae to flex both vertically and horizontally while preventing twisting motions. Such vertebrae are found in the necks of birds and some turtles.[20]

"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.

muscle surrounding the vertebral column does not lead to an opening between vertebrae.[24]

In many species, though not in mammals, the cervical vertebrae bear ribs. In many groups, such as

amniotes. In the whale the cervical vertebrae are typically fused, an adaptation trading flexibility for stability during swimming.[25][26] All mammals except manatees and sloths have seven cervical vertebrae, whatever the length of the neck.[27] This includes seemingly unlikely animals such as the giraffe, the camel, and the blue whale, for example. Birds
usually have more cervical vertebrae with most having a highly flexible neck consisting of 13–25 vertebrae.

In all mammals, the thoracic vertebrae are connected to

There are fewer lumbar vertebrae in chimpanzees and gorillas, which have three in contrast to the five in the genus Homo. 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.[31] The bonobo differs by having four lumbar vertebrae.

Caudal vertebrae are the bones that make up the tails of vertebrates.[32]
They range in number from a few to fifty, depending on the length of the animal's tail. In humans and other tailless
coccygeal vertebrae, number from three to five and are fused into the coccyx.[33]

Additional images

  • Vertebral arches of three thoracic vertebrae

    Vertebral arches of three thoracic vertebrae

  • Costovertebral joints seen from the front

    Costovertebral joints seen from the front

  • Lower thoracic and upper lumbar vertebrae seen from the side

    Lower thoracic and upper lumbar vertebrae seen from the side

  • Cervical vertebrae seen from the back

    Cervical vertebrae seen from the back

  • Vertebrae Anatomy

See also

References

Public domain This article incorporates text in the public domain from page 96 of the 20th edition of Gray's Anatomy (1918)

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  2. ^ McGraw-Hill Science and Technology[full citation needed]
  3. ^ O'Rahilly, Müller, Carpenter & Swenson. "Chapter 39: The vertebral column". Basic Human Anatomy. www.dartmouth.edu.{{cite web}}: CS1 maint: multiple names: authors list (link)
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  7. ^ Taylor, Tim. "Lumbar Vertebrae". InnerBody. Retrieved May 7, 2017.
  8. ^ , retrieved 2020-11-03
  9. ^ Standring, Susan (2008). "Thoracic vertebrae". Gray's Anatomy. p. 746.
  10. ^ Platzer (2004), pp 42–43
  11. ^ Latin costa refers to either a "rib" or "side" of the body. (Diab (1999), p 76)
  12. ^ a b Tweedie, A. The library of medicine p. 31
  13. ^ Heinz Feneis, Wolfgang Dauber (2000) Pocket Atlas of Human Anatomy: Based on the International Nomenclature p. 2
  14. , retrieved 2020-11-03
  15. ^ Postacchini, Franco (1999) Lumbar Disc Herniation p. 19
  16. ^ Drake et al, Gray's Anatomy for Students, Churchill Livingstone/Elsevier (2010), 2nd edition, chapter 2
  17. ^ a b Walker, Warren F., Jr. (1987) Functional Anatomy of the Vertebrate San Francisco: Saunders College Publishing.
  18. .
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  21. ^ Romer, Alfred (1962). The Vertebrate Body (3 ed.). Philadelphia, Pa; London, W.C.I.: W.B. Saunders Company.
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  23. ^ Romer, Alfred (1956). Osteology of the Reptiles. Malabar, Florida: Krieger Publishing Company. pp. 0–89464–985–X.
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  25. ^ "Beluga Whale". Yellowmagpie.com. 2012-06-27. Retrieved 2012-08-12.
  26. ^ "About Whales". Whalesalive.org.au. 2009-06-26. Retrieved 2013-08-12.
  27. . Retrieved May 7, 2017.
  28. ^ Hyman, Libbie (1922). Comparative Vertebrate Anatomy. Chicago: University of Chicago Press. pp. 123.
  29. ^ "Physical Characteristics of the Koala". Australian Koala Foundation. Retrieved 1 February 2012.
  30. ^ Hyman (1922), p. 124
  31. PMID 20855303.{{cite journal}}: CS1 maint: multiple names: authors list (link
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External links