sacrum

Information about sacrum

Bone: Sacrum
Sacrum, pelvic surface
Image of pelvis. Sacrum is in center.
Latinos sacrum
subject #24 106
MeSH Sacrum
Dorlands/Elsevier o_07/12598664


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).

It is curved upon itself and placed obliquely (that is, tilted forward). It is kyphotic - that is, concave facing forwards. 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.

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 because the sacrum was the part of an animal offered in sacrifice. In Slavic languages and in German this bone is called the "cross bone" [2].

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 apex (apex oss. sacri) is directed downward, and presents an oval facet for articulation with the coccyx.
  • The vertebral canal (canalis sacralis; sacral canal) runs throughout the greater part of the bone; above, it is triangular in form; below, its posterior wall is incomplete, from the non-development of the laminae and spinous processes. It lodges the sacral nerves, and its walls are perforated by the anterior and posterior sacral foramina through which these nerves pass out.

Articulations

The sacrum articulates with four bones: 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]

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).

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 [1]; occasionally the number is reduced to four [2]. 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.

The sacrum, also, varies considerably with respect to its degree of curvature

Additional images


Vertebral column.

Sacrum, dorsal surface.

Lateral surfaces of sacrum and coccyx.

Base of sacrum.

Median sagittal section of the sacrum.

Vertebral column.

Left Levator ani from within.

The posterior divisions of the sacral nerves.

Median sagittal section of male pelvis.

Median sagittal section of female pelvis.


See also

External links

References

1. ^ [3]
2. ^ [4]
3. ^ [5]]


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.
Spine [ edit]
general structures: body of vertebra, vertebral arch (pedicle, lamina, vertebral notch), foramina (vertebral, intervertebral), processes (transverse, articular, spinous) cervical vertebrae: C1 (anterior arch, posterior arch, lateral mass), C2 (dens), C7, posterior tubercle, foramen transversarium thoracic vertebrae: costal facets (superior, inferior, transverse) lumbar vertebrae: accessory process, mammillary process sacrum/coccyx: pelvic surface (anterior sacral foramina, dorsal surface (posterior sacral foramina, median sacral crest, medial sacral crest, lateral sacral crest), lateral surface, base, sacral hiatus
pelvis (pl. pelvises or pelves) is the bony structure located at the base of the spine (properly known as the caudal end). The pelvis incorporates the socket portion of the hip joint for each leg (in bipeds) or hind leg (in quadrupeds).
..... Click the link for more information.
Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
..... Click the link for more information.
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. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
..... Click the link for more information.
Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
..... Click the link for more information.
vertebral column (backbone or spine) is a column of 34 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsal aspect of the torso, separated by spinal discs. It houses the spinal cord in its spinal canal.
..... Click the link for more information.
The pelvic cavity is a body cavity that is bounded by the bones of the pelvis and which primarily contains reproductive organs, the urinary bladder, and the rectum.

Borders

The boundaries are as follows:
  • anterior: pubic symphysis

..... Click the link for more information.
The hip bone (or innominate bone) is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below. It is one of the few ball and socket synovial joints in the body.
..... Click the link for more information.
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.
..... Click the link for more information.
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.
..... Click the link for more information.
The Sacral promontory is the anatomical term for the superiormost portion of the sacrum. It marks part of the border of the pelvic inlet.

See also

  • Sacrovertebral angle

External links

  • SUNY Labs 43:st-0408

..... Click the link for more information.
sacrovertebral angle when articulated with the last lumbar vertebra.

See also

  • Sacral promontory
  • Pelvic inlet
This article was originally based on an entry from a public domain edition of Gray's Anatomy.
..... Click the link for more information.
The pelvic cavity is a body cavity that is bounded by the bones of the pelvis and which primarily contains reproductive organs, the urinary bladder, and the rectum.

Borders

The boundaries are as follows:
  • anterior: pubic symphysis

..... Click the link for more information.
Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
..... Click the link for more information.
Holiness, or sanctity, is the state of being holy or sacred, that is, set apart for the worship or service of God or gods. It is often ascribed to people, objects, times, or places.
..... Click the link for more information.
Greek}}} 
Writing system: Greek alphabet 
Official status
Official language of:  Greece
 Cyprus
 European Union
recognised as minority language in parts of:
 European Union
 Italy
 Turkey
Regulated by:
..... Click the link for more information.
Sacrifice (from a Middle English verb meaning "to make sacred", from Old French, from Latin sacrificium: sacer, sacred; sacred + facere, to make) is commonly known as the practice of offering food, or the lives of animals or people to the gods, as an act of propitiation or worship.
..... Click the link for more information.
The pelvic surface of sacrum is concave from above downward, and slightly so from side to side.

Its middle part is crossed by four transverse ridges, the positions of which correspond with the original planes of separation between the five segments of the bone.
..... Click the link for more information.
The dorsal surface of sacrum is convex and narrower than the pelvic.

In the middle line it displays a crest, the middle sacral crest, surmounted by three or four tubercles, the rudimentary spinous processes of the upper three or four sacral vertebrae.
..... Click the link for more information.
The lateral surface of sacrum is broad above, but narrowed into a thin edge below. The upper half presents in front an ear-shaped surface, the auricular surface, covered with cartilage in the fresh state, for articulation with the ilium.
..... Click the link for more information.
The base of the sacrum, which is broad and expanded, is directed upward and forward.

In the middle is a large oval articular surface, the upper surface of the body of the first sacral vertebra, which is connected with the under surface of the body of the last lumbar
..... Click the link for more information.
The spinal canal (or vertebral canal or spinal cavity) is the space in vertebrae through which the spinal cord passes. It is a process of the dorsal human body cavity. This canal is enclosed within the intervertebral foramen of the vertebrae.
..... Click the link for more information.
The five sacral nerves emerge from the sacrum. Although the vertebral components of the sacrum are fused into a single bone, the sacral vertebrae are still used to number the sacral nerves.
..... Click the link for more information.
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.
..... Click the link for more information.
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.
..... Click the link for more information.
The hip bone (or innominate bone) is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below. It is one of the few ball and socket synovial joints in the body.
..... Click the link for more information.
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. It is a strong, weightbearing synovial joint with irregular elevations and depressions that produce interlocking of the bones.
..... Click the link for more information.
Ilia or ILIA may refer to:
  • Ilia Prefecture, Greece
  • Ilia Province, Greece
  • Ilia (Star Trek), a character in Star Trek: The Motion Picture
  • Ilium (bone) (plural: "ilia"), pelvic bones
  • Illinois Institute of Art - Chicago (ILIA)

..... Click the link for more information.
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.

The nutation of a planet is due to the fact that the tidal forces which cause the precession of the equinoxes
..... Click the link for more information.
Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. Examples include size, color, and the presence or absence of parts of the body used in courtship displays or fights, such as ornamental feathers, horns, antlers or tusks.
..... Click the link for more information.
In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. Non-scientists often wonder why zoological and human anatomists use complex terminology to describe locations on a body, when common terms like "up",
..... Click the link for more information.

This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.