Sacrum

The large, heavy bone at the base of the spine, which is made up of fused sacral vertebrae. The sacrum is located in the vertebral column, between the lumbar vertebrae and the coccyx. It is roughly triangular in shape, and makes up the back wall of the pelvis. The female sacrum is wider and less curved than the male. See also pelvis, vertebral column, sacral vertebrae.

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The segment of the vertebral column forming part of the pelvis; a broad, slightly curved, spade-shaped bone, thick above, thinner below, closing in the pelvic girdle posteriorly; it is formed by the fusion of five originally separate sacral vertebrae; it articulates with the last lumbar vertebra, the coccyx, and the hip bone on either side. SYN: os s. [TA], sacred bone, vertebra magna. [L. (lit. sacred bone), neuter of sacer (sacr-), sacred]

- assimilation s. one which is composed of six segments, the last lumbar vertebra assuming the appearance of a sacral segment; or one which is composed of but four segments, the first sacral being free and having the characteristics of a lumbar vertebra.

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sa·crum 'sak-rəm, 'sā-krəm n, pl sa·cra 'sak-rə, 'sā-krə the part of the spinal column that is directly connected with or forms a part of the pelvis by articulation with the ilia and that in humans forms the dorsal wall of the pelvis and consists of five fused vertebrae diminishing in size to the apex at the lower end which bears the coccyx

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n. (pl. sacra)

a curved triangular element of the backbone consisting of five fused vertebrae (sacral vertebrae). It articulates with the last lumbar vertebra above, the coccyx below, and the hip bones laterally. See also vertebra.

• sacral adj.

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sa·crum (saґkrəm) [L. “sacred”] the triangular bone just below the lumbar vertebrae; see os sacrum [TA]. See illustration. sacral adj

Dorsal (A) and pelvic (B) surfaces of the sacrum and coccyx.