NationMaster - Encyclopedia: Coccyx

The coccyx (pronounced kok-siks) (Latin: os coccygis), commonly referred to as the tailbone, is the final segment of the human vertebral column, of four fused vertebrae (the coccygeal vertebrae) below the sacrum. It is attached to the sacrum in a fibrocartilaginous joint, which permits limited movement between them. The term coccyx comes originally from the Greek language and means "cuckoo," referring to the shape of a cuckoo's beak^[1]. File links The following pages link to this file: Coccyx Wikipedia:Grays Anatomy images with missing articles 2 Categories: Public domain images ... File links The following pages link to this file: Coccyx Wikipedia:Grays Anatomy images with missing articles 2 Categories: Public domain images ... A diagram of a thoracic vertebra. ... The vertebral column seen from the side The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ... A diagram of a thoracic vertebra. ... For the record label, see Sacrum Torch. ... For other uses, see Joint (disambiguation). ... Genera See text. ...

Function

The coccyx provides an attachment for nine muscles, such as the gluteus maximus, and those necessary for defecation. It also acts as something of a shock absorber when a person sits down, although forceful impact can cause damage and subsequent bodily pains. A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... The gluteus maximus is the largest and most superficial of the three gluteal muscles. ... Anatomy of the anus and rectum Defecation is the act or process by which organisms eliminate solid or semisolid waste material (feces) from the digestive tract via the anus. ... Gasfilled Shock absorber. ...

Structure

The coccyx is usually formed of four rudimentary vertebrae; the number may be as high as five or as low as three. It articulates superiorly with the sacrum. In each of the first three segments may be traced a rudimentary body and articular and transverse processes; the last piece (sometimes the third) is a mere nodule of bone. All the segments are destitute of pedicles, laminae, and spinous processes. The first is the largest; it resembles the lowest sacral vertebra, and often exists as a separate piece; the last three diminish in size from above downward. Most anatomy books wrongly state that the coccyx is normally fused in adults. In fact it has been shown^[2] ^[3] that the coccyx may consist of up to 5 separate bony segments, the most common configuration being two or three segments. Only about 5% of the population have a coccyx in one piece, separate from the sacrum, as described in anatomy books. This error in anatomy teaching can lead doctors to diagnose a 'fractured coccyx' when they see a coccyx in several segments on x-ray.^{[citation needed]} A diagram of a thoracic vertebra. ... For the record label, see Sacrum Torch. ... The pedicles are two short, thick processes, which project backward, one on either side, from the upper part of the body, at the junction of its posterior and lateral surfaces. ... The laminÃ¦ are two broad plates directed backward and medialward from the pedicles. ... The 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 the two hip bones. ...

Surfaces

The anterior surface is slightly concave, and marked with three transverse grooves which indicate the junctions of the different segments. It gives attachment to the anterior sacrococcygeal ligament and the Levatores ani, and supports part of the rectum. In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... The Anterior Sacrococcygeal Ligament consists of a few irregular fibers, which descend from the anterior surface of the sacrum to the front of the coccyx, blending with the periosteum. ... The Levator ani is a broad, thin muscle, situated on the side of the pelvis. ... The rectum (from the Latin rectum intestinum, meaning straight intestine) is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. ...

The posterior surface is convex, marked by transverse grooves similar to those on the anterior surface, and presents on either side a linear row of tubercles, the rudimentary articular processes of the coccygeal vertebrae. Of these, the superior pair are large, and are called the coccygeal cornua; they project upward, and articulate with the cornua of the sacrum, and on either side complete the foramen for the transmission of the posterior division of the fifth sacral nerve. The English word POSTERIOR is identical to the original Latin adjective, and has two different uses : as an ADJECTIVE, it indicates that someone or something is behind another, either spatially or chronologically it also became a SUBSTANTIVE, indicating the rear-end, especially of a person, i. ... The Sacral Nervesâ€”The posterior divisions of the sacral nerves (rami posteriores) are small, and diminish in size from above downward; they emerge, except the last, through the posterior sacral foramina. ...

Borders

The lateral borders are thin, and exhibit a series of small eminences, which represent the transverse processes of the coccygeal vertebrae. Of these, the first is the largest; it is flattened from before backward, and often ascends to join the lower part of the thin lateral edge of the sacrum, thus completing the foramen for the transmission of the anterior division of the fifth sacral nerve; the others diminish in size from above downward, and are often wanting. The borders of the coccyx are narrow, and give attachment on either side to the sacrotuberous and sacrospinous ligaments, to the Coccygeus in front of the ligaments, and to the gluteus maximus behind them. The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis. ... The Coccygeus is situated behind the levator ani. ... The gluteus maximus is the largest of the gluteus muscles which are located in the buttock. ...

Apex

The apex is rounded, and has attached to it the tendon of the Sphincter ani externus. It may be bifid. The Sphincter ani externus (external anal sphincter) is a flat plane of muscular fibers, elliptical in shape and intimately adherent to the integument surrounding the margin of the anus. ... Spina bifida (Latin: split spine) is a developmental birth defect involving the neural tube: incomplete closure of the embryonic neural tube results in an incompletely formed spinal cord. ...

Sacrococcygeal and intercoccygeal joints

The joints are variable and may be: (1) synovial joints; (2) thin discs of fibrocartilage; (3) intermediate between these two; (4) ossified.^[4] ^[5] Synovial joints (or diarthroses, or diarthroidal joints) are the most common and most moveable type of joints in the body. ... Cartilage is type of dense connective tissue. ...

Pathology

Injuring the coccyx can give rise to a condition called coccydynia. ^[6] ^[7] Coccydynia is a medical condition characterized by pain in the coccyx or tailbone area. ...

Additional images

See also

Coccydynia is a medical condition characterized by pain in the coccyx or tailbone area. ... This article is about the skeletal organs. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... The pelvic portion of each sympathetic trunk is situated in front of the sacrum, medial to the anterior sacral foramina. ... The muscles connected to the ears of a human do not develop enough to have the same mobility allowed to monkeys. ...

References

External links

Categories: All articles with unsourced statements | Articles with unsourced statements since October 2007 | Skeletal system An illustration from the 1918 edition Henry Grays Anatomy of the Human Body (or Grays Anatomy as it has more commonly become known) is an anatomy textbook widely regarded as a classic work on human anatomy. ... The State University of New York Health Science Center at Brooklyn, better known as SUNY Downstate Medical Center, is an academic medical center and is the only one of its kind in the Borough of Brooklyn in New York City. ... The Medical University of Vienna , formerly the faculty of medicine of the University of Vienna, became an independent university on January 1, 2004. ... This article is about the skeletal organs. ... The human torso Torso is an anatomical term for the greater part of the human body without the head and limbs. ... The sternum (from Greek ÏƒÏ„ÎÏÎ½Î¿Î½, sternon, chest) or breastbone is a long, flat bone located in the center of the thorax (chest). ... This article needs to be cleaned up to conform to a higher standard of quality. ... Sternum or breastbone is a long, flat bone located in the center of the thorax (chest). ... The sternal angle is the angle formed by the junction of the manubrium and the body of the sternum. ... The body of the sternum (gladiolus), considerably lengthier, narrower, and thinner than the manubrium, attains its greatest breadth close to the lower end. ... The xiphisternal joint (or xiphisternal synchondrosis) is a location near the bottom of the sternum, where the following two parts of the sternum meet: body of the sternum xiphoid process It is in line with the T9 vertebrae. ... The xiphoid process is a small cartilaginous extension to the lower part of the sternum which is usually ossified in the adult human. ... The human rib cage. ... The first rib is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward. ... The second rib is much longer than the first, but has a very similar curvature. ... The tenth rib has only a single articular facet on its head. ... The eleventh rib has a single articular facet on the head, which is of rather large size. ... The twelfth rib has a single articular facet on the head, which is of rather large size. ... Excluding the first seven ribs, the remaining five are false ribs. ... the four floating ribs Four of the ribs (two pairs) in the ribcage are said to be floating ribs because they are attached to the vertebrae only, and not to the sternum or cartilage coming off of the sternum. ... The external surface of the rib is convex, smooth, and marked, a little in front of the tubercle, by a prominent line, directed downward and laterally; this gives attachment to a tendon of the Iliocostalis, and is called the angle. ... On the posterior surface at the junction of the neck and body of the rib, and nearer the lower than the upper border, is an eminenceâ€”the tubercle It consists of an articular and a non-articular portion. ... Between the ridge of the interal surface of the rib and the inferior border is a groove, the costal groove, for the intercostal vessels and intercostal nerve. ... The neck of the rib is the flattened portion which extends lateralward from the head; it is about 2. ... The head of the rib is marked by a kidney-shaped articular surface, divided by a horizontal crest into two facets for articulation with the depression formed on the bodies of two adjacent thoracic vertebrae; the upper facet is the smaller; to the crest is attached the interarticular ligament. ... The body is the largest part of a vertebra, and is more or less cylindrical in shape. ... The vertebral arch (or neural arch) is the posterior part of a vertebra. ... The pedicles are two short, thick processes, which project backward, one on either side, from the upper part of the body, at the junction of its posterior and lateral surfaces. ... The laminÃ¦ are two broad plates directed backward and medialward from the pedicles. ... The concavities above and below the pedicles are named the vertebral notches; and when the vertebrae are articulated, the notches of each contiguous pair of bones form the intervertebral foramina. ... In a typical vertebra, the vertebral foramen is the foramen formed by the anterior segment (the body), and the posterior part, the vertebral arch. ... When the spinal vertebrae are articulated with each other the bodies form a strong pillar for the support of the head and trunk, and the vertebral foraminae constitute a canal for the protection of the medulla spinalis (spinal cord). ... The transverse processes of a vertebra, two in number, project one at either side from the point where the lamina joins the pedicle, between the superior and inferior articular processes. ... The articular processes of a vertebra, two superior and two inferior, spring from the junctions of the pedicles and laminÃ¦. The superior project upward, and their articular surfaces are directed more or less backward; the inferior project downward, and their surfaces look more or less forward. ... A zygapophysis is process which sticks out of an end of a vertebra to lock with a zygapophysis on the next vertebra, to make the backbone more stable. ... A diagram of a thoracic vertebra. ... In vertebrates, cervical vertebrae (singular: vertebra) are those vertebrae immediately behind (caudal to) the skull. ... In anatomy, the atlas (C1) is the topmost (first) cervical vertebra of the spine. ... The anterior arch of the atlas forms about one-fifth of the ring of the atlas: its anterior surface is convex, and presents at its center the anterior tubercle for the attachment of the Longus colli muscles; posteriorly it is concave, and marked by a smooth, oval or circular facet... In a cervical vertebra, the posterior arch forms about two-fifths of the circumference of the ring: it ends behind in the posterior tubercle, which is the rudiment of a spinous process and gives origin to the Recti capitis posteriores minores. ... The lateral masses are the most bulky and solid parts of the atlas, in order to support the weight of the head. ... In anatomy, the second cervical vertebra (C2) of the spine is named the axis or epistropheus. ... The dens or odontoid process or odontoid peg of the axis exhibits a slight constriction or neck, where it joins the body. ... The most distinctive characteristic of the seventh cervical vertebra is the existence of a long and prominent spinous process, hence the name vertebra prominens. ... The anterior arch forms about one-fifth of the ring: its anterior surface is convex, and presents at its center the anterior tubercle for the attachment of the Longus colli muscles. ... The posterior arch of a cervical vertebra forms about two-fifths of the circumference of the ring: it ends behind in the posterior tubercle, which is the rudiment of a spinous process and gives origin to the Recti capitis posteriores minores. ... The transverse processes of the cervical vertebrae are each pierced by the foramen transversarium, which, in the upper six vertebrÃ¦, gives passage to the vertebral artery and vein and a plexus of sympathetic nerves. ... A typical thoracic vertebra The thoracic vertebrae (vertebrae thoracales) compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. ... The superior costal facet (or superior costal fovea) is a site where a rib forms a joint with the top of a vertebra. ... The inferior costal facet (or inferior costal fovea) is a site where a rib forms a joint with the bottom of a vertebra. ... The transverse costal facet (or transverse costal fovea) is a site where a rib forms a joint with the transverse process of a vertebra. ... The lumbar vertebrae are the largest segments of the movable part of the vertebral column, and are characterized by the absence of the foramen transversarium within the transverse process, and by the absence of facets on the sides of the body. ... Of the tubercles noticed in connection with the transverse processes of the lower thoracic vertebrae, the inferior is situated at the back part of the base of the transverse process, and is called the accessory process. ... Of the three tubercles noticed in connection with the transverse processes of the lower thoracic vertebrae, the superior one is connected in the lumbar region with the back part of the superior articular process, and is named the mammillary process. ... For the record label, see Sacrum Torch. ... The pelvic surface of sacrum is concave from above downward, and slightly so from side to side. ... At the ends of the transverse ridges of the pelvic surface of the sacrum are seen the anterior sacral foramina (or pelvic sacral foramina), four in number on either side, somewhat rounded in form, diminishing in size from above downward, and directed lateralward and forward; they give exit to the... The dorsal surface of sacrum is convex and narrower than the pelvic. ... Lateral to the articular processes of the sacrum are the four posterior sacral foramina (or dorsal sacral foramina); they are smaller in size and less regular in form than the anterior, and transmit the posterior divisions of the sacral nerves. ... In the middle line of the dorsal surface of the sacrum, it displays a crest, the median sacral crest, surmounted by three or four tubercles, the rudimentary spinous processes of the upper three or four sacral vertebrae. ... On the lateral aspect of the sacral groove is a linear series of tubercles produced by the fusion of the articular processes which together form the indistinct medial sacral crest (intermediate sacral crest, sacral articular crest). ... On the lateral side of the posterior sacral foramina is a series of tubercles, which represent the transverse processes of the sacral vertebrae, and form the lateral sacral crest. ... The lateral surface of sacrum is broad above, but narrowed into a thin edge below. ... The base of the sacrum, which is broad and expanded, is directed upward and forward. ... The laminae of the fifth sacral vertebra, and sometimes those of the fourth, fail to meet behind, and thus a sacral hiatus or deficiency occurs in the posterior wall of the sacral canal. ... In human anatomy, the presacral space is behind the rectum and in front of the coccyx. ... The Sacral promontory is the anatomical term for the anteriormost portion of the sacrum. ...

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