| sacral hiatus | A normally-occurring gap at the lower end of the sacrum, exposing the vertebral canal, due to failure of the laminae of the last sacral segment to coalesce. It is closed by the sacrococcygeal ligament, and provides cannular access to the sacral epidural space for administration of anaesthetics (caudal nerve blocks). Synonym: hiatus sacralis. (05 Mar 2000) |
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| sacral horns | The most caudal parts of the intermediate sacral crest. On each side they form the lateral margin of the sacral hiatus and articulate with the coccygeal cornua. Synonym: cornua sacralia, sacral horns. (05 Mar 2000) |
| sacral index | A ratio obtained by multiplying the greatest breadth of the sacrum by 100 and dividing by the length. (05 Mar 2000) |
| sacral lymph nodes | Nodes in the concavity of the sacrum that drain the rectum and posterior pelvic wall. Synonym: nodi lymphatici sacrales. (05 Mar 2000) |
| sacral nerves | Five nerves issuing from the sacral foramina on either side; the ventral branches of the first three enter into the formation of the sacral plexus, and the last two into the coccygeal plexus. Synonym: nervi sacrales. (05 Mar 2000) |
| sacral part of spinal cord | The part of the cord from which consists of the five sacral segments of the spinal cord (S1-S5) and from which five pairs of sacral nerves originate. Synonym: pars sacralis medullae spinalis, segmenta medullae spinalis sacralia. (05 Mar 2000) |
| sacral plexus | Formed by the fourth and fifth lumbar (lumbosacral trunk) and first, second, and third sacral nerves; it lies on the inner surface of the posterior wall of the pelvis usually embedded in the piriformis muscle; its nerves supply the lower limbs, its major product being the sciatic nerve. Synonym: plexus sacralis, ischiadic plexus, sciatic plexus. (05 Mar 2000) |
| sacral promontory | The most prominent anterior projection of the base of the sacrum. Synonym: pelvic promontory, promontorium ossis sacri, promontory of the sacrum. (05 Mar 2000) |
| sacral region | The area of the back overlying the sacrum. Synonym: regio sacralis. (05 Mar 2000) |
| sacral splanchnic nerves | Branches from the sacral sympathetic trunk that pass to the inferior hypogastric plexus; part of the abdominopelvic (sympathetic) splanchnic nerves, but their specific function is unclear. They tend to be confused with the pelvic splanchnic nerves, which are much more significant structures. Synonym: nervi splanchnici sacrales. (05 Mar 2000) |
| sacral triangle | The surface area over the sacrum. (05 Mar 2000) |
| sacral tuberosity | A rough prominence on the lateral surface of the sacrum posterior to the auricular surface for attachment of posterior sacroiliac ligaments. Synonym: tuberositas sacralis. (05 Mar 2000) |
| sacral veins | See: lateral sacral veins, median sacral vein. (05 Mar 2000) |
| sacral venous plexus | A venous plexus on the pelvic surface of the sacrum, formed by tributaries to the lateral sacral veins. Synonym: plexus venosus sacralis. (05 Mar 2000) |
| sacral vertebrae | The segments of the vertebral column, usually five in number, that fuse to form the sacrum. Synonym: vertebrae sacrales. (05 Mar 2000) |