| apex of sacrum | The tapering lower end of the sacrum that articulates with the coccyx. Synonym: apex ossis sacri. (05 Mar 2000) |
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| auricular surface of sacrum | The rough articular surface on the lateral aspect of the sacrum that articulates with the ilium on each side. Synonym: facies auricularis ossis sacri. (05 Mar 2000) |
| base of sacrum | The upper end of the sacrum that articulates with the body of the fifth lumbar vertebra in the midline and the alae on either side. Synonym: basis ossis sacri. (05 Mar 2000) |
| pelvic surface of sacrum | The surface of the sacrum that faces downward and forward forming part of the posterior wall of the pelvic cavity. Synonym: facies pelvina ossis sacri. (05 Mar 2000) |
| wing of sacrum | The upper surface of the lateral part of the sacrum adjacent to the body. Synonym: ala sacralis. (05 Mar 2000) |
| sacrum | <anatomy> The triangular-shaped bone lying between the 5th lumbar vertebra and the coccyx (tailbone). It consists of 5 vertebrae fused together and it articulates on each side with the bones of the pelvis (ilium), forming the sacroiliac joints. (17 Dec 1997) |
| promontory of the sacrum | The most prominent anterior projection of the base of the sacrum. Synonym: pelvic promontory, promontorium ossis sacri, promontory of the sacrum. (05 Mar 2000) |
| superior articular process of sacrum | The large process on each side of the sacrum posteriorly that articulates with the corresponding inferior articular process of the fifth lumbar vertebra. Synonym: processus articularis superior ossis sacri. (05 Mar 2000) |
| dorsal surface of sacrum | The posterosuperior aspect of the sacrum marked by a median and two lateral sacral crests between which four dorsal sacral foramina are located on each side. Synonym: facies dorsalis ossis sacri. (05 Mar 2000) |
| os sacrum | <anatomy> The triangular-shaped bone lying between the 5th lumbar vertebra and the coccyx (tailbone). It consists of 5 vertebrae fused together and it articulates on each side with the bones of the pelvis (ilium), forming the sacroiliac joints. (17 Dec 1997) |
| transverse lines of sacrum | One of four ridges that cross the pelvic surface of the sacrum; these mark the positions of the intervertebral disks between the bodies of the five sacral vertebrae in the immature bone. Synonym: lineae transversa ossi sacri. (05 Mar 2000) |
| lateral part of sacrum | The lateral mass of the sacrum formed by the fused costal elements. Synonym: pars lateralis ossis sacri. (05 Mar 2000) |