NationMaster - Encyclopedia: Sacrum

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. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx (tailbone). Image File history File links Circle-question-red. ... File links The following pages link to this file: Sacrum Wikipedia:Grays Anatomy images with missing articles 2 Categories: Public domain images ... Image File history File links Gray241. ... The pelvis (pl. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Elseviers logo. ... Sacrum Torchs logo. ... The vertebral column seen from the side Different regions (curvatures) of the vertebral column The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ... The Pelvic cavity is a body cavity that is bounded by the bones of the pelvis and which primarily contains reproductive organs. ... The hip bone (or innominate bone) is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below. ... The lumbar vertebrae are the largest segments of the movable part of the vertebral column, and can be distinguished by the absence of a foramen (hole) in the transverse process, and by the absence of facets on the sides of the body. ... The coccyx is formed of up to five vertebrae. ...

It is curved upon itself and placed obliquely (that is, tilted forward). It is concave facing forwards, thus its curvature is considered a kyphosis. The base projects forward as the sacral promontory internally, and articulates with the last lumbar vertebra to form the prominent sacrovertebral angle. The central part is curved outward towards the posterior, allowing greater room for the pelvic cavity. Kyphosis, in general terms, is a curvature of the upper spine. ... The Sacral promontory is the anatomical term for the anteriormost portion of the sacrum. ... The sacrum is curved upon itself and placed very obliquely, its base projecting forward and forming the prominent sacrovertebral angle when articulated with the last lumbar vertebra. ... 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 Pelvic cavity is a body cavity that is bounded by the bones of the pelvis and which primarily contains reproductive organs. ...

Etymology

The name is derived from the Latin sacer, "sacred", a translation of the Greek hieron (osteon), meaning sacred or strong bone.^[1] This is supposedly derived from the belief that it could not be destroyed and was the part that would allow rising from the dead.^[2]^{[citation needed]} In Slavonic languages this bone is called the cross bone. Two of them symbolise passage of time. In bone chapel is a main cross formed by assembly of 4 sacrum bones. It hurts like hell to break, so be careful.... I have done this before, and trust me, the broccoli knows... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... In various religions, sacred (from Latin, sacrum, sacrifice) or holy, objects, places or concepts are believed by followers to be intimately connected with the supernatural, or divinity, and are thus greatly revered. ...

Parts

The pelvic surface of sacrum is concave from above downward, and slightly so from side to side. ... The dorsal surface of sacrum is convex and narrower than the pelvic. ... 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 spinal canal (or vertebral canal) is the space in vertebrae through which the spinal cord passes. ... 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. ...

Articulations

Although in most people the sacro-iliac joints are tightly bound and immobile, some are able to rotate the sacrum forward a few degrees vis-à-vis the ilia. This motion is sometimes called "nutation", and the reverse motion "counter-nutation."^[3] A typical lumbar vertebra The lumbar vertebrae are the largest segments of the movable part of the vertebral column, and can be distinguished by the absence of a foramen (hole) in the transverse process, and by the absence of facets on the sides of the body. ... The coccyx is formed of up to five vertebrae. ... The hip bone (or innominate bone) is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below. ... The sacroiliac joint is the joint between the sacrum, at the base of the spine, and the ilium of the pelvis, which are joined by ligaments. ... Ilia, or ILIA, can refer to: The Prefecture of Ilia in Greece Ilia, Hunedoara is a commune in Hunedoara County, Romania Jointly, ILIA is the Illinois Institute of Art - Schaumburg and Illinois Institute of Art - Chicago[1] Rhea Sylvia, also known as Ilia, is in Roman mythology the mother of... Rotation (green), Precession (blue) and Nutation (red) of the Earth Nutation is a slight irregular motion (etymologically a nodding) in the axis of rotation of a largely axially symmetric object, such as a gyroscope or a planet. ...

It is called the sacrum when referred to all of the parts combined, but sacral vertebrae when referred individually.

Sexual dimorphism

The sacrum is noticeably sexually dimorphic (differently-shaped in males and females). Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size between the sexes Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. ...

In the female the sacrum is shorter and wider than in the male; the lower half forms a greater angle with the upper; the upper half is nearly straight, the lower half presenting the greatest amount of curvature. The bone is also directed more obliquely backward; this increases the size of the pelvic cavity and renders the sacrovertebral angle more prominent.

In the male the curvature is more evenly distributed over the whole length of the bone, and is altogether greater than in the female.

Variations

The sacrum, in some cases, consists of six pieces; occasionally the number is reduced to four. The bodies of the first and second vertebrae may fail to unite.

Sometimes the uppermost transverse tubercles are not joined to the rest of the ala on one or both sides, or the sacral canal may be open throughout a considerable part of its length, in consequence of the imperfect development of the laminae and spinous processes.

Additional images

See also

Grays Anatomy illustration of a human femur. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... Pelvimetry is the assessment of the female pelvis is relation to the birth of a baby. ...

External links

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 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. ... eMedicine is an online clinical medical knowledge base that was founded in 1996. ...

References

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant. The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ... 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. ...

Categories: Cleanup from December 2006 | Wikipedia articles needing clarification | Articles with unsourced statements since February 2007 | All articles with unsourced statements | Irregular bones | Pelvis Grays Anatomy illustration of a human femur. ... 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). ... Sternum or breastbone is a long, flat bone located in the center of the thorax (chest). ... The body of the sternum (gladiolus), considerably lengthier, narrower, and thinner than the manubrium, attains its greatest breadth close to the lower end. ... The xiphoid process is a small cartilaginous extension to the lower part of the sternum which is usually ossified in the adult human. ... This article needs to be cleaned up to conform to a higher standard of quality. ... 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 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. ... 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. ... Excluding the first seven ribs, the remaining five are false ribs. ... 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 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 can be distinguished by the absence of a foramen (hole) in 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. ... The coccyx is formed of up to five vertebrae. ... 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. ...

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