Sacrum ( lat. Os sacrum , literally "sacred bone" [comm. 1] ) - part of the spine of terrestrial vertebrates , providing its connection with the pelvis . It is located between the lumbar and caudal (in the human - coccygeal ) vertebrae .
|lat os sacrum|
Human sacral bone, pelvic surface.
Taz . The sacral bone is in the center.
In modern amphibians , the sacrum includes 1 vertebra, in modern reptiles - 2, in mammals - 1-2 truly sacral vertebrae fuse with several anterior caudal vertebrae, in birds - 2 truly sacral vertebrae fuse together not only with the anterior caudal vertebrae, but also with all the lumbar and hind chest ( complex sacrum ). In vertebrates that have lost hind limbs, the sacrum is not pronounced   .
The human sacrum is a large triangular bone of 5 fused vertebrae  . It forms the upper back of the pelvic cavity, like a wedge located between two pelvic bones. The upper part of the sacrum connects with the last lumbar vertebra , the lower - with the coccyx .
- 1 The structure of the human sacrum
- 2 Connections
- 3 Sex differences
- 4 See also
- 5 notes
The structure of the human sacrum
- The front (pelvic) surface ( facies pelvica ) is concave - more in the upper-lower and less in the lateral directions. In the middle part it is intersected by four parallel transverse lines that represent the fusion sites of five separate sacral vertebrae. Anterior sacral openings are located on both sides of these lines - four on each side. The holes are approximately round in shape, directed forward and sideways, and their diameter decreases from top to bottom. They pass the anterior branches of the sacral nerves and the lateral sacral arteries. Laterally of these openings are the lateral parts of the sacrum, each of which is formed by five segments in the early stages of life, and in an adult it merges into a single structure.
- The back surface ( facies dorsalis ) is convex and narrower than the front, rough. It carries five parallel scallops that run parallel downward, which were formed by the fusion of the spinous, transverse and articular processes of the sacral vertebrae. The middle, formed by the spinous processes, the sacral scallop is represented by four tubercles, which are the residual processes. Sometimes the tubercles can merge into one rough scallop.
- Lateral surfaces ( pars lateralis ) are wide in the upper part and taper downward. Connections with the pelvic bones are carried out using a large number of ligaments and saddle joints of the L-shaped form. The mobility of the joints provides the inclination of the sacrum forward and backward, as well as torsion (tilt with rotation) when walking. A small volume of movement and loading of the sacroiliac joints often leads to immobility, as a result of which the function of these joints is transferred to the hip joints and to the L5-S1 joint, an increase in load leads to the gradual development of coxarthrosis and protrusion / hernia of the intervertebral disc.
- The base of the sacrum ( basis ossis sacri ) is wide and protruding, facing up and forward. Its front edge at the junction with the V lumbar vertebra forms a prominent protrusion in the pelvic cavity - the cape.
- The top of the sacrum ( apex ossis sacri ) is turned down, represented by an oval articular surface for connection with the coccyx.
- The sacral canal ( canalis sacralis ) runs along the entire length of the bone, has a curved shape, is widened at the top and has a triangular shape, the canal is narrowed at the bottom, and its posterior wall is not filled. The sacral nerves pass through the canal, which exit through the anterior and posterior sacral openings.
- With V lumbar vertebra
- With tailbone
- With pelvic bones on both sides
The dorsal surface of the sacrum, facies dorsalis, is convex in the longitudinal direction, already anterior and rough. On it there are five adjacent bone ridges extending from top to bottom, resulting from the fusion of the spinous, transverse and articular processes of the sacral vertebrae. The median sacral crest, Crista sacralis mediana, was formed from the fusion of the spinous processes of the sacral vertebrae and is represented by four tubercles located one above the other, sometimes merging into one rough crest.
In women, the sacral bone is shorter, wider and less curved than in men.
- Sacroiliac Joint
- Sacral brain
- The origin of the name is not exactly known. It was used even in antiquity and can originate in ancient Greek or even ancient Egyptian culture   .
- Foundational Model of Anatomy
- Sugar O. How the sacrum got its name ( Journal ) // Journal of the American Medical Association : journal. - 1987. - Vol. 257 , no. 15 . - P. 2061-2063 . - DOI : 10.1001 / jama.1987.03390150077038 . - PMID 3550163 .
- Wilson JA Anatomical Terminology for the Sacrum of Sauropod Dinosaurs // Contributions from the Museum of Paleontology, University of Michigan: journal. - 2011 .-- Vol. 32 , no. 5 . - P. 59-69 .
- Sacrum // Biological Encyclopedic Dictionary / Ch. ed. M.S. Gilyarov ; Editorial: A.A. Baev , G.G. Vinberg, G.A. Zavarzin et al. - M .: Sov. Encyclopedia , 1986.- S. 293.- 831 p. - 100,000 copies.
- Sacral / Sukhanov V. B. // Great Soviet Encyclopedia : [in 30 vol.] / Ch. ed. A.M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.
- Cherkasov V.G., Kravchuk S. Yu. Human anatomy . - Vinnitsa: Nova Kniga, 2014 .-- S. 35. - 584 p. - ISBN 9789663825144 .