| C3 | third cervical nerve; third cervical vertebra; third component of complement |
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| C4 | fourth cervical nerve; fourth cervical vertebra; fourth component of complement |
| C5 | fifth cervical nerve; fifth cervical vertebra; fifth component of complement |
| C6 | sixth cervical nerve; sixth cervical vertebra; sixth component of complement |
| C7 | seventh cervical nerve; seventh cervical vertebra; seventh component of complement |
| spina dorsalis | The series of vertebrae that extend from the cranium to the coccyx, providing support and forming a flexible bony case for the spinal cord. Synonym: columna vertebralis, backbone, dorsal spine, rachis, spina dorsalis, spina, spina, spinal column, spine, vertebrarium. (05 Mar 2000) |
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| spina frontalis | S, nasalis ossis frontalis. (05 Mar 2000) |
| spina helicis | An anteriorly directed spine at the extremity of the crus of the helix of the auricle. Synonym: spina helicis, apophysis helicis. (05 Mar 2000) |
| spina iliaca anterior inferior | Spine on the anterior border of the ilium between the anterior superior iliac spine and the acetabulum; site of origin for the direct head of the rectus femoris muscle. Synonym: spina iliaca anterior inferior. (05 Mar 2000) |
| spina iliaca anterior superior | The anterior extremity of the iliac crest, which provides attachment for the inguinal ligament and the sartorius muscle. Synonym: spina iliaca anterior superior. (05 Mar 2000) |
| spina iliaca posterior inferior | Spine at the inferior end of the posterior border of the ilium between the posterior superior iliac spine and the greater sciatic notch; it forms the upper margin of the latter. Synonym: spina iliaca posterior inferior. (05 Mar 2000) |
| spina iliaca posterior superior | The posterior extremity of the iliac crest, the uppermost point of attachment of the sacrotuberous and posterior sacroiliac ligaments; a readily apparent dimple occurs in the skin overlying the posterior superior iliac spine which is clinically useful as an indication of the level of the S-2 vertebra, the level of the inferior limit of the subarachnoid space. Synonym: spina iliaca posterior superior. (05 Mar 2000) |
| spina ischiadica | A pointed process from the posterior border of the ischium on a level with the lower border of the acetabulum; gives attachment to the sacrospinous ligament; the pudendal nerve passes dorsal to the ischial spine, which is palpable per vagina or rectum, and thus is used as a target for the needle-tip in administering a pudendal nerve block. Synonym: spina ischiadica, ischiadic spine, sciatic spine. (05 Mar 2000) |
| spina meatus | Small bony prominence anterior to the supramastoid pit at the posterosuperior margin of the bony external acoustic meatus. Synonym: spina suprameatica, Henle's spine, meatal spine, spina meatus. (05 Mar 2000) |
| spina mentalis | A slight projection, sometimes two, in the middle line of the posterior surface of the body of the mandible, giving attachment to the geniohyoid muscle (below) and the genioglossus (above). Synonym: spina mentalis, genial tubercle. (05 Mar 2000) |
| spina nasalis anterior | A pointed projection at the anterior extremity of the intermaxillary suture; the tip, as seen on a lateral cephalometric radiograph, is used as a cephalometric landmark. Synonym: spina nasalis anterior. (05 Mar 2000) |
| spina nasalis ossis frontalis | A projection from the centre of the nasal part of the frontal bone, which lies between and articulates with the nasal bones and the perpendicular plate of the ethmoid. Synonym: spina nasalis ossis frontalis. (05 Mar 2000) |
| spina nasalis posterior | The sharp posterior extremity of the nasal crest of the hard palate. Synonym: spina nasalis posterior, posterior palatine spine. (05 Mar 2000) |
| spina ossis sphenoidalis | A posterior and downward projection from the greater wing of the sphenoid bone on either side, located posterolateral to the foramen spinosum, so-named for its proximity to the sphenoidal spine; gives attachment to the sphenomandibular ligament. Synonym: processus spinosus, spina ossis sphenoidalis, alar spine, angular spine, spina angularis, spinous process. (05 Mar 2000) |
| spina pedis | An obsolete term for a hard or soft corn. (05 Mar 2000) |