Sacrum

The sacrum (Latin os sacrum ) is a bone of land vertebrates. In adult humans it is approximately wedge-shaped. It evolved through fusion ( synostosis ) of the original single, growing together vertebrae, called the sacral vertebrae. In adolescents this merger ( a cartilaginous composite ago ) until the end of the growth phase takes place. The sacrum encloses the posterior portion of the spinal canal and forms with the coxal one unit, the pelvic girdle.

Vertebrae

The number of fused vertebrae varies within the class of mammals between three (eg, dogs) and five (humans, horses). The individual vertebrae are ( transversae lineae ) by Verwachsungslinien still be seen.

In a few people the original upper sacral vertebra (S1 ) is not as common with the other sacral vertebrae fused ( lumbalization ). So, these people seem to have six lumbar vertebrae instead of five. This has definitely mean a greater mobility of the spine and can result in a lower carrying capacity of the spine, but does not usually cause discomfort.

Caudal ( tail down) - ie in animals and humans back down - joins the tailbone ( coccyx ) or the tail spine.

Exiting nerve

The emerging from the sacral spinal nerves form a network together with shares of emerging from the lower lumbar nerves - the lumbosacral plexus. From this tangle of nerves that supply the pelvis and legs mainly form.

Anatomy

The sacrum still has despite the merger all the basic characteristics of the vertebrae.

The former spinous form, artlich differerierenden in the ridge, the median sacral crest. The individual, very long spinous processes ( spinous processes ) usually remain isolated only in horses.

Back to top (with animals in front) is on a small extension ( cranial articular process ) on each side an articular surface for the last lumbar vertebra. The remaining articular processes form in some species ( eg human, ruminant ) a strip-like elevation ( sacral crest intermedia).

The transverse processes form a wide plate, the pars lateralis ( " side part " ) in all mammals. The front part of the side part is enlarged in animals to the sacrum (ala of the sacrum ). This is in all mammals ( including humans) on both sides of an ear-shaped articular surface (facies auricular ), which forms the respective sacroiliac joint ( sacroiliac joint) with the same joint surface of the ilium. Attach the pelvis to the hull. The side edge of the lateral part is referred to as the lateral sacral crest.

The pars lateralis shares the openings for the spinal nerves. So find each dorsal side of which the sacral foramina dorsalia that serve the Dorsalästen of sacral spinal nerves to exit, and basin- ward the sacral foramina pelvina for the corresponding Ventraläste.

Special

As Sacrum Arcuate refers to a particularly strong curved sacrum.

Movement possibilities

The movement of the sacrum is called nutation or counternutation. Here, the promontory moved to ventrocaudal ( down and forward ) and the lower surface (apex of the sacrum ), to which the tailbone ( coccyx ) followed, after dorsokranial ( up and back ). So it is in the sacrum -iliac joint ( sacroiliac joint ), not only to a rotation, but also to a shift of the surfaces against each other.

In the cranio- sacral therapy several axes of motion are postulated, the upper transverse axis (OTA ), the mean transverse axis (MTA ) - nutation and counternutation -, the lower transverse axis (UTA ), a cranio- caudal axis and a right and left diagonal axis.

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