A diagram of a thoracic vertebra. Notice the articulations for the ribs

Different regions of the vertebral column

The Vertebral column (singular: vertebra) are the individual irregular bones that make up the spinal column (aka ischis) — a flexuous and flexible column common to all Vertebrates. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce In Vertebrate Anatomy, ribs ( Latin costae) are the long curved Bones which form the ribcage. In Human anatomy, the vertebral column ( backbone or spine) is a column of 34 Vertebrae the Sacrum, Intervertebral In Human anatomy, the vertebral column ( backbone or spine) is a column of 34 Vertebrae the Sacrum, Intervertebral The irregular bones are bones which from their peculiar form cannot be grouped as Long bone, Short bone, Flat bone or Sesamoid bone. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes

There are normally thirty-three (33) vertebrae in humans, including the five that are fused to form the sacrum (the others are separated by intervertebral discs) and the four coccygeal bones which form the tailbone. The sacrum is a large triangular bone at the base of the spine and at the upper and back part of the Pelvic cavity, where it is inserted like a wedge between Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine. The coccyx (pronounced kok -siks (Latin os coccygis) commonly referred to as the tailbone, is the final segment of the human vertebral column Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce The upper three regions comprise the remaining 24, and are grouped under the names cervical (7 vertebrae), thoracic (12 vertebrae) and lumbar (5 vertebrae), according to the regions they occupy. This number is sometimes increased by an additional vertebra in one region, or it may be diminished in one region, the deficiency often being supplied by an additional vertebra in another. The number of cervical vertebrae is, however, very rarely increased or diminished.

With the exception of the first and second cervical, the true or movable vertebrae (the upper three regions) present certain common characteristics which are best studied by examining one from the middle of the thoracic region.

General structure

Oblique view of cervical vertebrae

A typical vertebra consists of two essential parts: an anterior (front) segment, which is the vertebral body; and a posterior part – the vertebral (neural) arch – which encloses the vertebral foramen. 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. In a typical Vertebra, the vertebral foramen is the Foramen formed by the anterior segment (the body) and the posterior part the Vertebral arch The vertebral arch is formed by a pair of pedicles and a pair of laminae, and supports seven processes, four articular, two transverse, and one spinous, the latter also being known as the neural spine. The pedicles (from Latin pediculus, "small foot" are two short thick processes which project backward one on either side from the upper part of the body at the The laminæ are two broad plates directed backward and medially from the pedicles. In Anatomy, a process ( Latin: processus) is a projection or outgrowth of tissue from a larger body

When the vertebrae are articulated with each other, the bodies form a strong pillar for the support of the head and trunk, and the vertebral foramina constitute a canal for the protection of the medulla spinalis (spinal cord). In Anatomy, the head of an Animal is the Rostral part (from Anatomical position that usually comprises the Brain, Eyes Torso is an anatomical term for the central part of the many animal bodies (including that of the human from which extend the neck and limbs The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected In between every pair of vertebrae are two apertures, the intervertebral foramina, one on either side, for the transmission of the spinal nerves and vessels. 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 foramina constitute a canal

Two transverse processes and one spinous process are posterior to (behind) the vertebral body. 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 The spinous process of a Vertebra is directed backward and downward from the junction of the laminae (in humans and serves for the attachment of Muscles The spinous process comes out the back, one transverse process comes out the left, and one on the right. The spinous processes of the cervical and lumbar regions can be felt through the skin. Superior and inferior articular facets on each vertebra act to restrict the range of movement possible. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce A zygapophysial joint ( zygapophyseal, or facet joint) is a Synovial joint between the superior articular process of one Vertebra and These facets are joined by a thin portion of the neural arch called the pars interarticularis. The pars interarticularis is the part of Vertebra located between the inferior and superior Articular processes of the Facet joint.

Regions

Orientation of vertebral column on surface. T3 is at level of medial part of spine of scapula. The spine of the scapula is a prominent plate of Bone, which crosses obliquely the medial four-fifths of the dorsal surface of the Scapula at its upper part and separates T7 is at inferior angle of the scapula. The inferior angle of the Scapula, thick and rough is formed by the union of the vertebral and axillary borders its dorsal surface affords attachment to the Teres major L4 is at highest point of iliac crest. The crest of the ilium (or iliac crest) is the superior border of the Wing of ilium and the superolateral margin of the Greater pelvis. S2 is at the level of posterior superior iliac spine. The posterior border of the ala, shorter than the anterior also presents two projections separated by a notch the posterior superior iliac spine and the Posterior inferior iliac Furthermore, C7 is easily localized as a prominence at the lower part of the neck. ^[1]

Cervical

Note: For more detailed information, see Cervical vertebrae

These are generally small and delicate. In Vertebrates cervical vertebrae (singular vertebra) are those vertebrae immediately behind (posterior to the Skull. Their spinous processes are short (with the exception of C2 and C7, which have palpable spinous processes), and often split. Numbered top-to-bottom from C1-C7, atlas (C1) and axis (C2), are the vertebrae that allow the neck and head so much movement. In Anatomy, the atlas (C1 is the topmost (first Cervical vertebra of the spine. In Anatomy, the second Cervical vertebra (C2 of the spine is named the axis (from Latin axis, "axle" or epistropheus. The neck is the part of the Body on many limbed Vertebrates that distinguishes the head from the Torso or trunk In Anatomy, the head of an Animal is the Rostral part (from Anatomical position that usually comprises the Brain, Eyes For the most part, 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. The Atlanto-occipital joint ( articulation between the atlas and the Occipital bone) consists of a pair of Condyloid joints The Atlanto-axial joint ( articulation of the atlas with the axis) is of a complicated nature comprising no fewer than four distinct joints The axis also sits upon the first intervertebral disk of the spinal column. All mammals except manatees and sloths have seven cervical vertebrae, whatever the length of the neck. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Manatees ( family Trichechidae, Genus Trichechus) are large fully aquatic Marine mammals sometimes known as sea The living sloths comprise six Species of medium-sized Mammals that live in Central and South America belonging to the families

Thoracic

Note: For more detailed information, see Thoracic vertebrae

Their spinous processes have surfaces that articulate with the ribs. The 12 thoracic vertebrae compose the middle segment of the Vertebral column, between the Cervical vertebrae and the Lumbar vertebrae. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce In Vertebrate Anatomy, ribs ( Latin costae) are the long curved Bones which form the ribcage. Some rotation can occur between the thoracic vertebrae, but their connection with the rib cage prevents much flexion or other excursion. They may also be known as 'dorsal vertebrae', in the human context.

Lumbar

Note: For more detailed information, see Lumbar vertebrae

These vertebrae are very robust in construction, as they must support more weight than other 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 They allow significant flexion and extension, moderate lateral flexion (sidebending), and a small degree of rotation. The discs between these vertebrae create a lumbar lordosis (curvature that is concave posteriorly) in the human spine. In Anatomy, lumbar is an Adjective that means of or pertaining to the Abdominal segment of the Torso, between the diaphragm and

Sacral

Note: For more detailed information, see Sacral vertebrae

There are 5 vertebrae (S1-S5). The sacrum is a large triangular bone at the base of the spine and at the upper and back part of the Pelvic cavity, where it is inserted like a wedge between They are fused in maturity, with no intervertebral discs. Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine.

Coccygeal

Note: For more detailed information, see Coccygeal vertebrae

There are 3-5 vertebrae (Co1-Co5), again fused, with no intervertebral discs. The coccyx (pronounced kok -siks (Latin os coccygis) commonly referred to as the tailbone, is the final segment of the human vertebral column Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine. Many animals have a greater number of "tail vertebrae" and, in animals, they are more commonly known as "caudal vertebrae. " Pain at the coccyx (tailbone) is known as coccydynia. The coccyx (pronounced kok -siks (Latin os coccygis) commonly referred to as the tailbone, is the final segment of the human vertebral column Coccydynia is a medical term meaning pain in the Coccyx or tailbone area usually brought on by sitting

Development

The striking segmented pattern of the human spine is established during embryogenesis when the precursor of the vertebrae, the somites, are rhythmically added to the forming posterior part of the embryo. In human, somite formation begins around the third week post-fertilization and continues until a total of around 52 somites are formed. The somites are epithelial spheres that contain the precursors of the vertebrae, the ribs, the skeletal muscles of the body wall and limbs, and the dermis of the back. The periodicity of somite distribution and production is thought to be imposed by a molecular oscillator or clock acting in cells of the presomitic mesoderm (PSM). Somites form soon after the beginning of gastrulation, on both sides of the neural tube from a tissue called the presomitic mesoderm (PSM). The PSM is part of the paraxial mesoderm and is generated caudally by gastrulation when cells ingress through the primitive streak, and later, through the tail bud. Soon after their formation, somites become subdivided into the dermomyotome dorsally, which gives rise to the muscles and dermis, and the sclerotome ventrally which will form the spine components. Sclerotomes become subvidided into an anterior and a posterior compartment. This subdivision plays a key role in the definitive patterning of vertebrae which form when the posterior part of one somite fuses to the anterior part of the consecutive somite during a process termed resegmentation. Disruption of the somitogenesis process in humans results in diseases such as congenital scoliosis. So far, the human homologues of three genes associated to the mouse segmentation clock (MESP2, DLL3 and LFNG) have been shown to be mutated in human patients with human congenital scoliosis suggesting that the mechanisms involved in vertebral segmentation are conserved across vertebrates. In humans the first four somites are incoporated in the basi-occipital bone of the skull and the next 33 somites will form the vertebrae. The remaining posterior somites degenerate. During the fourth week of embryonic development, the sclerotomes shift their position to surround the spinal cord and the notochord. Embryogenesis is the process by which the Embryo is formed and develops A sclerotome is part of a Somite, a structure in vertebrate embryonic development. The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected The notochord is a flexible rod-shaped body found in Embryos of all Chordates It is composed of cells derived from the Mesoderm and defines the The sclerotome is made of mesoderm and originates from the ventromedial part of the somites. A germ layer is a collection of cells formed during animal Embryogenesis. A somite is a division of the body of an animal In vertebrates this is mainly discernible in the embryo stage in arthropods it is a characteristic of a hypothetical ancestor This column of tissue has a segmented appearance, with alternating areas of dense and less dense areas.

As the sclerotome develops, it condenses further eventually developing into the vertebral body. The body is the largest part of a Vertebra, and is more or less cylindrical in shape Development of the appropriate shapes of the vertebral bodies is regulated by HOX genes. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance

The less dense tissue that separates the sclerotome segments develop into the intervertebral discs. Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine.

The notochord disappears in the sclerotome (vertebral body) segments, but persists in the region of the intervertebral discs as the nucleus pulposus. Nucleus pulposus is the jelly-like substance in the middle of the Spinal disc. The nucleus pulposus and the fibers of the annulus fibrosus make up the intervertebral disc. Each Intervertebral fibrocartilage is composed at its circumference of laminæ of fibrous tissue and Fibrocartilage, forming the annulus fibrosus.

The primary curves (thoracic and sacral curvatures) form during fetal development. The secondary curves develop after birth. The cervical curvature forms as a result of lifting the head and the lumbar curvature forms as a result of walking.

There are various defects associated with vertebral development. Scoliosis can result from improper fusion of the vertebrae. Scoliosis is a medical condition in which a person's spine is curved from side to side and may also be rotated In Klippel-Feil anomaly patients have two or more cervical vertebrae that are fused together, along with other associated birth defects. Klippel-Feil syndrome is a rare disorder initially reported in 1912 by Maurice Klippel and Andre Feil from France characterized by the congenital fusion of any 2 One of the most serious defects is failure of the vertebral arches to fuse. This results in a condition called spina bifida. Spina bifida ( Latin: "split spine" is a developmental Birth defect involving the Neural tube: incomplete closure of the Embryonic neural There are several variations of spina bifida that reflect the severity of the defect.

Footnotes

References

• Gray's Anatomy: The Vertebral column - The 1917 Gray's Anatomy is available via the Bartleby project. Year 1917 ( MCMXVII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common year Henry Gray's Anatomy of the Human Body (or Gray's Anatomy as it has commonly been shortened is an English-language Human anatomy Textbook It is available with full colour diagrams, and provides an excellent starting point in anatomy, as well as a relatively complete source for gross anatomy. Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration Gross anatomy is the study of Anatomy at the macroscopic level. This article was copied and pasted from the 1917 Gray's Anatomy, which is in the public domain. The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone
• Smart implant will help broken vertebra - An article from IsraCast