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. The basic configuration of a vertebra varies; the upper and lower surfaces of the vertebra body give attachment to the intervertebral discs. The posterior part of a vertebra forms a vertebral arch, in eleven parts, consisting of two pedicles, two laminae, seven processes; the laminae give attachment to the ligamenta flava. There are vertebral notches formed from the shape of the pedicles, which form the intervertebral foramina when the vertebrae articulate; these foramina are the exit conducts for the spinal nerves. 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. Vertebrae articulate with each other to give strength and flexibility to the spinal column, the shape at their back and front aspects determines the range of movement.
Structurally, vertebrae are 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; each vertebra is an irregular bone. The size of the vertebrae varies according to placement in the vertebral column, spinal loading and pathology. Along the length of the spine the vertebrae change to accommodate different needs related to stress and mobility; every vertebra has a body, which consists of a large anterior middle portion called the centrum and a posterior vertebral arch called a neural arch. The body is composed of cancellous bone, the spongy type of osseous tissue, whose micro-anatomy has been studied within the pedicle bones; this cancellous bone is in turn, covered by a thin coating of cortical bone, the hard and dense type of osseous tissue. The vertebral arch and processes have thicker coverings of cortical bone; the upper and lower surfaces of the body of the vertebra are flattened and rough in order to give attachment to the intervertebral discs.
These surfaces are the vertebral endplates which are in direct contact with the intervertebral discs and form the joint. The endplates are formed from a thickened layer of the cancellous bone of the vertebral body, the top layer being more dense; the endplates function to contain the adjacent discs, to evenly spread the applied loads, to provide anchorage for the collagen fibers of the disc. They act as a semi-permeable interface for the exchange of water and solutes; 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, 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; the upper surfaces of the laminae are rough to give attachment to the ligamenta flava.
These ligaments connect the laminae of adjacent vertebra along the length of the spine from the level of the second cervical vertebra. Above and below the pedicles are shallow depressions called vertebral notches; when the vertebrae articulate the notches align with those on adjacent vertebrae and these form the openings of the 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. There are seven processes projecting from the vertebra. A major part of a vertebra is a backward extending spinous process; this process points caudally from the junction of the laminae. The spinous process serves to attach ligaments; the two transverse processes, one on each side of the vertebral body, project from either side at the point where the lamina joins the pedicle, between the superior and inferior articular processes. They serve for the attachment of muscles and ligaments, in particular the intertransverse ligaments.
There is a facet on each of the transverse processes of thoracic vertebrae which articulates with the tubercle of the rib. A facet on each side of the thoracic vertebral body articulates with the head of the rib. 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. The transverse process of a lumbar vertebra is sometimes called the costal or costiform process because it corresponds to a rudimentary rib which, as opposed to the thorax, is not developed in the lumbar region. Vertebrae take their names from the regions of the vertebral column. 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; the regional vertebrae increase in size as they become smaller in the coccyx.
There are seven cervical vertebrae
The intervertebral foramen, is a foramen between two spinal vertebrae. Cervical and lumbar vertebrae all have intervertebral foramina; the foramina, or openings, are present between every pair of vertebrae in these areas. A number of structures pass through the foramen; these are the root of each spinal nerve, the spinal artery of the segmental artery, communicating veins between the internal and external plexuses, recurrent meningeal nerves, transforaminal ligaments. When the spinal vertebrae are articulated with each other, the bodies form a strong pillar that supports the head and trunk, the vertebral foramen constitutes a canal for the protection of the medulla spinalis; the size of the foramina is variable due to placement, spinal loading, posture. Foramina can be occluded by arthritic degenerative changes and space-occupying lesions like tumors and spinal disc herniations; the intervertebral foramen is bordered by the superior notch of the adjacent vertebra, the inferior notch of the vertebra, the intervertebral joint and the intervertebral disc.
This article incorporates text in the public domain from page 96 of the 20th edition of Gray's Anatomy Diagram at emory.edu "Anatomy diagram: 06363.008-2". Roche Lexicon - illustrated navigator. Elsevier. Archived from the original on 2014-01-01. Skeleton2/intervertebralforamen Photo of model at Waynesburg College Intervertebral foramina - BlueLink Anatomy - University of Michigan Medical School
Loyola University Chicago
Loyola University Chicago is a private Catholic research university in Chicago, Illinois. Founded in 1870 by the Jesuits, today Loyola is one of the largest Catholic universities in the United States. Loyola's professional schools have educated generations of local business and civic leaders, distinguished programs in medicine and health sciences are anchored by the nationally recognized Loyola University Medical Center. Comprising eleven colleges and schools, Loyola offers over 80 undergraduate and 140 graduate/professional programs and enrolls 16,000 students. Loyola has six campuses across the Chicago metropolitan area, as well as a campus in Rome and guest programs in Beijing and Ho Chi Minh City; the flagship Lake Shore Campus is on the shores of Lake Michigan in the Rogers Park and Edgewater neighborhoods of Chicago, eight miles north of the Loop. Loyola's athletic teams, nicknamed the Ramblers, compete in NCAA Division I as members of the Missouri Valley Conference. Loyola won the 1963 NCAA men's basketball championship, remains the only school from Illinois to do so.
The Ramblers are two-time NCAA champions in men's volleyball. Among the more than 150,000 Loyola alumni, there are executives of major Chicago-based corporations such as McDonald's and Baxter International, as well as dozens of local and national political leaders including the current Illinois Attorney General and Speaker of the House. Loyola alumni have won Emmy, Grammy and Pulitzer awards, as well as Guggenheim and MacArthur fellowships. Loyola was established as St. Ignatius College on June 30, 1870, by Jesuit educator Fr. Arnold Damen. At that time Chicago was a much smaller, but growing, city just shy of 300,000 people, as a result the original campus was much closer to the city center along Roosevelt Road. In 1909 the school was renamed Loyola University, in 1912 it began to move to the current Lake Shore Campus. To meet the growing needs of Chicago, Loyola established professional schools in law, medicine and nursing; the Chicago College of Dental Surgery became part of the university in 1923, was closed 70 years later.
A downtown campus was founded in 1914, with it the School of Sociology. As the predecessor to the School of Social Work, it enrolled Loyola's first female students, though the school would not become coeducational until 1966. Loyola Academy, a college prep high school, occupied Dumbach Hall on the Lake Shore Campus until it was relocated to north suburban Wilmette in 1957; the current Water Tower Campus opened in 1949. In 1962, Loyola opened a campus in Rome near the site of the 1960 Summer Olympics. In 1969, Loyola established the School of Education and consolidated medical programs at the Loyola University Medical Center, a hospital and health care complex located in Maywood, an immediate suburb of Chicago; the university separated from the Jesuits in 1970, today is under lay control and governed by a board of trustees. Loyola purchased neighboring Mundelein College in 1991. Major capital campaigns since the turn of the century have enhanced Loyola's academic profile and campuses. In 2005 the Loyola University Museum of Art was established on the Water Tower Campus, the Rome campus was renamed in honor of Director Emeritus John P. Felice.
In 2009, the Cuneo Foundation presented the university with the Cuneo Mansion and Gardens, a 100-acre estate with an Italianate mansion and extensive collections of art and furnishings located in suburban Vernon Hills. The $50 million gift is the largest in Loyola history. In 2010, Loyola purchased the Resurrection Retreat Center in Woodstock, which became the school's fifth campus for retreat and ecological study. In 2012, Loyola alumnus Michael R. Quinlan donated $40 million to the business school, renamed in his honor. During this time over 200,000 square-feet of LEED-certified sustainable spaces have been built on the Lake Shore Campus alone, along with significant mixed-use developments on the Water Tower Campus. Today, Loyola ranks among the top 89 universities in the nation, is in the midst of over $800 million in capital construction projects. In 2015, the university established Arrupe College, a uniquely structured two-year college designed to give low-income students access to a Loyola education.
On May 23, 2016, Loyola named Jo Ann Rooney its 24th president. She is the first female president in the history of the university. Loyola's flagship Lake Shore Campus is along the shores of Lake Michigan in the Rogers Park and Edgewater neighborhoods on the north side of Chicago, eight miles north of the Loop. Founded in 1912, it is the primary residential campus for the school, is the home of the College of Arts and Sciences, a variety of graduate programs. A collection of over forty buildings, the campus offers ample green space and lakeshore access, as well as several landmarks: The Madonna della Strada Chapel, a striking Art Deco masterpiece completed in 1939, is the center of Loyola's religious life; the Mundelein Center, a 200-foot tall Art Deco skyscraper completed in 1930, is the home of Loyola's fine and performing arts programs and a National Historical Landmark. The Joseph J. Gentile Arena, which holds 5,500 for basketball and campus events, was expanded to include the Norville Center, a student-athlete academic center and home of Rambler athletics.
One of the largest events held annually in Gentile Arena is Colossus, which features a musical artist and comedian. Artists including Jason Derulo and John Mulaney have performed for Colossus; the Halas Recreation Center was remodeled and incorp
In anatomy, the atlas is the most superior cervical vertebra of the spine. It is named for the Atlas of Greek mythology, because it supports the globe of the head, the skull; the atlas is the topmost vertebra and with the axis forms the joint connecting the spine. The atlas and axis are specialized to allow a greater range of motion than normal vertebrae, they are responsible for the nodding and rotation movements of the head. The atlanto-occipital joint allows the head to nod down on the vertebral column; the dens acts as a pivot that allows the atlas and attached head to rotate on the axis, side to side. The atlas's chief peculiarity is, it consists of an anterior and a posterior arch and two lateral masses. The atlas and axis are important neurologically; the anterior arch forms about one-fifth of the ring: its anterior surface is convex, presents at its center the anterior tubercle for the attachment of the Longus colli muscles and the anterior longitudinal ligament. The upper and lower borders give attachment to the anterior atlantooccipital membrane and the anterior atlantoaxial ligament.
The posterior arch forms about two-fifths of the circumference of the ring: it ends behind in the posterior tubercle, the rudiment of a spinous process and gives origin to the Recti capitis posteriores minores and the ligamentum nuchae. The diminutive size of this process prevents any interference with the movements between the atlas and the skull; the posterior part of the arch presents above and behind a rounded edge for the attachment of the posterior atlantooccipital membrane, while behind each superior articular process is the superior vertebral notch. This is a groove, sometimes converted into a foramen by ossification of the posterior atlantooccipital membrane to create a delicate bony spiculum which arches backward from the posterior end of the superior articular process; this anatomical variant is known as an arcuate foramen. This groove transmits the vertebral artery, after ascending through the foramen in the transverse process, winds around the lateral mass in a direction backward and medially to enter the vertebrobasilar circulation through the foramen magnum.
The lower border gives attachment to the posterior atlantoaxial ligament, which connects it with the axis. The lateral masses are the most bulky and solid parts of the atlas, in order to support the weight of the head; each carries a superior and an inferior. The superior facets are of large size, oval and approach each other in front, but diverge behind: they are directed upward, a little backward, each forming a cup for the corresponding condyle of the occipital bone, are admirably adapted to the nodding movements of the head. Not infrequently they are subdivided by indentations which encroach upon their margins; the inferior articular facets are circular in form, flattened or convex and directed downward and medially, articulating with the axis, permitting the rotatory movements of the head. Just below the medial margin of each superior facet is a small tubercle, for the attachment of the transverse atlantal ligament which stretches across the ring of the atlas and divides the vertebral foramen into two unequal parts: the anterior or smaller receiving the odontoid process of the axis the posterior transmitting the spinal cord and its membranesThis part of the vertebral canal is of considerable size, much greater than is required for the accommodation of the spinal cord.
The transverse processes are large. They are long, their anterior and posterior tubercles are fused into one mass; the atlas is ossified from three centers. Of these, one appears in each lateral mass about the seventh week of fetal life, extends backward. Between the third and fourth years they unite either directly or through the medium of a separate center developed in the cartilage. At birth, the anterior arch consists of cartilage; the lines of union extend across the anterior portions of the superior articular facets. There is no separate center, the anterior arch being formed by the forward extension and ultimate junction of the two lateral masses. Upper surface: rectus capitis anterior – occipital bone rectus capitis lateralis – occipital bone obliquus capitis superior – occipital bone Interior and dorsal part: obliquus capitis inferior – spinous process of the axisLower surface: splenius cervicis – spinous processes of T02–T05 levator scapulae – superior part of medial border of the scapula intertransversarius posterior cervici
Chicago the City of Chicago, is the most populous city in Illinois, as well as the third most populous city in the United States. With an estimated population of 2,716,450, it is the most populous city in the Midwest. Chicago is the principal city of the Chicago metropolitan area referred to as Chicagoland, the county seat of Cook County, the second most populous county in the United States; the metropolitan area, at nearly 10 million people, is the third-largest in the United States, the fourth largest in North America and the third largest metropolitan area in the world by land area. Located on the shores of freshwater Lake Michigan, Chicago was incorporated as a city in 1837 near a portage between the Great Lakes and the Mississippi River watershed and grew in the mid-nineteenth century. After the Great Chicago Fire of 1871, which destroyed several square miles and left more than 100,000 homeless, the city made a concerted effort to rebuild; the construction boom accelerated population growth throughout the following decades, by 1900 Chicago was the fifth largest city in the world.
Chicago made noted contributions to urban planning and zoning standards, including new construction styles, the development of the City Beautiful Movement, the steel-framed skyscraper. Chicago is an international hub for finance, commerce, technology, telecommunications, transportation, it is the site of the creation of the first standardized futures contracts at the Chicago Board of Trade, which today is the largest and most diverse derivatives market gobally, generating 20% of all volume in commodities and financial futures. O'Hare International Airport is the one of the busiest airports in the world, the region has the largest number of U. S. highways and greatest amount of railroad freight. In 2012, Chicago was listed as an alpha global city by the Globalization and World Cities Research Network, it ranked seventh in the entire world in the 2017 Global Cities Index; the Chicago area has one of the highest gross domestic products in the world, generating $680 billion in 2017. In addition, the city has one of the world's most diversified and balanced economies, not being dependent on any one industry, with no single industry employing more than 14% of the workforce.
Chicago's 58 million domestic and international visitors in 2018, made it the second most visited city in the nation, behind New York City's approximate 65 million visitors. The city ranked first place in the 2018 Time Out City Life Index, a global quality of life survey of 15,000 people in 32 cities. Landmarks in the city include Millennium Park, Navy Pier, the Magnificent Mile, the Art Institute of Chicago, Museum Campus, the Willis Tower, Grant Park, the Museum of Science and Industry, Lincoln Park Zoo. Chicago's culture includes the visual arts, film, comedy and music jazz, soul, hip-hop and electronic dance music including house music. Of the area's many colleges and universities, the University of Chicago, Northwestern University, the University of Illinois at Chicago are classified as "highest research" doctoral universities. Chicago has professional sports teams in each of the major professional leagues, including two Major League Baseball teams; the name "Chicago" is derived from a French rendering of the indigenous Miami-Illinois word shikaakwa for a wild relative of the onion, known to botanists as Allium tricoccum and known more as ramps.
The first known reference to the site of the current city of Chicago as "Checagou" was by Robert de LaSalle around 1679 in a memoir. Henri Joutel, in his journal of 1688, noted that the eponymous wild "garlic" grew abundantly in the area. According to his diary of late September 1687:...when we arrived at the said place called "Chicagou" which, according to what we were able to learn of it, has taken this name because of the quantity of garlic which grows in the forests in this region. The city has had several nicknames throughout its history such as the Windy City, Chi-Town, Second City, the City of the Big Shoulders, which refers to the city's numerous skyscrapers and high-rises. In the mid-18th century, the area was inhabited by a Native American tribe known as the Potawatomi, who had taken the place of the Miami and Sauk and Fox peoples; the first known non-indigenous permanent settler in Chicago was Jean Baptiste Point du Sable. Du Sable arrived in the 1780s, he is known as the "Founder of Chicago".
In 1795, following the Northwest Indian War, an area, to be part of Chicago was turned over to the United States for a military post by native tribes in accordance with the Treaty of Greenville. In 1803, the United States Army built Fort Dearborn, destroyed in 1812 in the Battle of Fort Dearborn and rebuilt; the Ottawa and Potawatomi tribes had ceded additional land to the United States in the 1816 Treaty of St. Louis; the Potawatomi were forcibly removed from their land after the Treaty of Chicago in 1833. On August 12, 1833, the Town of Chicago was organized with a population of about 200. Within seven years it grew to more than 4,000 people. On June 15, 1835, the first public land sales began with Edmund Dick Taylor as U. S. Receiver of Public Monies; the City of Chicago was incorporated on Saturday, March 4, 1837, for several decades was the world's fastest-growing city. As the site of the Chicago Portage, the city became an important transportation hub between the eastern and western United States.
Chicago's first railway and Chicago Union Railroad, the Illi
The lumbar vertebrae are, in human anatomy, the five vertebrae 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 and by the absence of facets on the sides of the body, they are designated L1 to L5, starting at the top. The lumbar vertebrae help support the weight of the body, permit movement; the figure on the left depicts the general characteristics of the first through fourth lumbar vertebrae. The fifth vertebra contains certain peculiarities; as with other vertebrae, each lumbar vertebra consists of a vertebral arch. The vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen and supports seven processes; the vertebral body of each lumbar vertebra is large, wider from side to side than from front to back, a little thicker in front than in back. It is flattened or concave above and below, concave behind, constricted in front and at the sides.
The pedicles are strong, directed backward from the upper part of the vertebral body. 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. The laminae are broad 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 connects the spinous process to the pedicles. The vertebral foramen within the arch is triangular, larger than the thoracic vertebrae, but smaller than in the cervical vertebrae; the spinous process is thick and somewhat quadrilateral. The superior and inferior articular processes are well-defined, projecting upward and downward from the junctions of pedicles and laminae.
The facets on the superior processes are concave, look backward and medialward. 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; the transverse processes are 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, are homologous with the ribs. Three portions or tubercles can be noticed in a transverse process of a lower lumbar vertebrae: the lateral or costiform process, the mammillary process, the accessory process; the costiform is lateral, the mammillary is superior, the accessory is inferior. 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 that of L5; the first lumbar vertebra is level with the anterior end of the ninth rib. This level is called the important transpyloric plane, since the pylorus of the stomach is at this level. Other important structures are located at this level, they include; 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. The fifth lumbar vertebra is by far the most common site of spondylolisthesis. Most individuals have five lumbar vertebrae, while some have six. Lumbar disorders that affect L5 will affect L4 or L6 in these latter individuals; the range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but because it is age and gender dependent. Furthermore 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 lumbal spine are: Congenital vertebral anomalies can cause compression of the spinal cord by deforming the vertebral canal or causing instability. African apes have three and four lumbar vertebrae, humans five; this difference, because the lumbar spines of the extinct Nacholapithecus are similar to those of early Australopithecus and early Homo, it is assumed that the Chimpanzee-human last common ancestor had a long vertebral column with a l
In vertebrates, cervical vertebrae are the vertebrae of the neck below the skull. Thoracic vertebrae in all mammalian species are those vertebrae that carry a pair of ribs, lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which belong to the trunk, but do not carry ribs. In reptiles, all trunk vertebrae are called dorsal vertebrae. In many species, though not in mammals, the cervical vertebrae bear ribs. In many other groups, such as lizards and saurischian dinosaurs, the cervical ribs are large; the vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes. Most mammals have 7 cervical vertebrae. In humans, cervical vertebrae are the smallest of the true vertebrae, can be distinguished from those of the thoracic or lumbar regions by the presence of a foramen in each transverse process, through which the vertebral artery, vertebral veins and inferior cervical ganglion pass; the remainder of this article focuses upon human anatomy.
By convention, the cervical vertebrae are numbered, with the first one closest to the skull and higher numbered vertebrae proceeding away from the skull and down the spine. The general characteristics of the third through sixth cervical vertebrae are described here; the first and seventh vertebrae are extraordinary, are detailed later. The bodies of these four vertebrae are small, broader from side to side than from front to back; the anterior and posterior surfaces are flattened and of equal depth. The upper surface is concave transversely, presents a projecting lip on either side; the lower surface is concave from front to back, convex from side to side, presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra. The pedicles are directed laterally and backward, attach to the body midway between its upper and lower borders, so that the superior vertebral notch is as deep as the inferior, but it is, at the same time, narrower; the laminae are narrow, thinner above than below.
The spinous process is short and bifid, the two divisions being of unequal size. Because the spinous processes are so short, certain superficial muscles attach to the nuchal ligament rather than directly to the vertebrae; the superior and inferior articular processes of cervical vertebrae have fused on either or both sides to form articular pillars, columns of bone that project laterally from the junction of the pedicle and lamina. The articular facets are flat and of an oval form: the superior face backward and medially; the inferior face forward and laterally. The transverse processes are each pierced by the foramen transversarium, which, in the upper six vertebrae, gives passage to the vertebral artery and vein, as well as a plexus of sympathetic nerves; each process consists of a posterior part. These two parts are joined, outside the foramen, by a bar of bone that exhibits a deep sulcus on its upper surface for the passage of the corresponding spinal nerve; the anterior portion is the homologue of the rib in the thoracic region, is therefore named the costal process or costal element.
It arises from the side of the body, is directed laterally in front of the foramen, ends in a tubercle, the anterior tubercle. The posterior part, the true transverse process, springs from the vertebral arch behind the foramen, is directed forward and laterally; the anterior tubercle of the sixth cervical vertebra is known as the carotid tubercle or Chassaignac tubercle. This separates the carotid artery from the vertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms of supraventricular tachycardia; the carotid tubercle is used as a landmark for anaesthesia of the brachial plexus and cervical plexus. The cervical spinal nerves emerge from above the cervical vertebrae. For example, the cervical spinal nerve 3 passes above C3; the atlas and axis are the two topmost vertebrae. The atlas, C1, is the topmost vertebra, along with the axis, its chief peculiarity is that it has no body because the body of the atlas has been fused with that of the axis. The axis, C2, forms the pivot.
The most distinctive characteristic of this bone is the strong odontoid process that rises perpendicularly from the upper surface of the body. The body is deeper in front than behind, prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra; the vertebra prominens, or C7, has a distinctive long and prominent spinous process, palpable from the skin surface. Sometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a cervical rib, which develops from the anterior root of the transverse process; these ribs are small, but may compress blood vessels or nerves in the brachial plexus, causing pain, numbness and weakness in the upper limb, a condition known as thoracic outlet syndrome. This rib occurs in a pair; the long spinous process of C7 is thick and nearly horizontal in dire