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The sacrum (pl.: sacra or sacrums [1]), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1–S5) between ages 18 and 30. [2] The sacrum situates at the upper, back part of the pelvic cavity, between the two wings of the pelvis. It forms joints with four other bones.
This structure can only be seen in birds. Some posterior thoracic vertebrae, the lumbar, sacral and a few anterior caudal vertebrae are fused to form a complex bone called synsacrum. The innominate bones are fused with the synsacrum to a greater or lesser extent, according to species, forming an avian pelvis. This forms a more extensive rigid ...
Vertebrae take their names from the regions of the vertebral column that they occupy. There are usually thirty-three vertebrae in the human vertebral column — seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, five fused sacral vertebrae forming the sacrum and four coccygeal vertebrae, forming the coccyx.
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
The thoracic vertebrae number between five and ten, and the first thoracic vertebra is distinguishable due to the fusion of its attached rib to the sternum while the ribs of cervical vertebrae are free. [7] Anterior thoracic vertebrae are fused in many birds and articulate with the notarium of the pectoral girdle. [13]
A coccyx with four vertebrae below the sacrum. The coccyx is formed of three, four or five rudimentary vertebrae.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.
The sacrals, or sacral vertebrae, of the vertebral column are located between the dorsal and caudal vertebrae. They are frequently fused together into a structure known as the sacrum (plural: sacra). [1]: 143 Sometimes one or more dorsal vertebrae are fused to the sacrum into a structure termed a synsacrum. [48]: 368
The most common findings are lower limb fusion into a single extremity, deformities of the sacrum and pelvic girdle, absence of external genitalia, absence of anal patency, and lethal renal ...