HEAD AND ANTERIOR CERVICAL STRUCTURES. 



61 



Sacral and coccygeal nerves, 828. (808-9) 



Internal branches. External branches. 

 Lower two sacral and the coccygeal nerve. 

 Rotatores spinze, 449. (444) 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. 

 Interspinales, 449-50. (444) 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. 

 Intertransversales, 449-50. (445) 



Structure. Nerve-supply. Relations. 

 Levatores costarum, 421 ; Fig. 299. (418) 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. 

 Ligamentum nuchae, 1250. (1226) 

 Spinal veins, 667-8 ; Fig. 390. (653-4) 

 Extraspinal and intraspinal. 



The extraspinal veins: 

 Anterior spinal plexus. 

 Posterior spinal or dorsal spinal plexus. 



In the suboccipital triangle trace the branches and expose the posterior primary division of the first cer- 

 vical nerve. 



Posterior primary division of the first cervical nerve, 826-7. (806-7) 

 The Suboccipital Muscles, 450-1 ; Fig. 308. (445-6) 

 Rectus capitis posticus major : 



Origin. Insertion. Structure. 

 Rectus capitis posticus minor: 



Origin. Insertion. Structure. 

 Obliquus capitis inferior: 



Origin. Insertion. Structure. 

 Obliquus capitis superior: 



Origin. Insertion. Structure. 

 Rectus capitis lateral is, Fig. 316. 



Origin. Insertion. Structure. 



Variations. 



Vertebral artery, 540; Fig. 342. (532) 



The second or vertebral portion. 

 Vertebral artery, 540-1 ; Fig. 342. (532). 

 The third or occipital portion. 



In front. Behind. 



Branches of the occipital artery, 520 ; Fig. 335. (511-12) 

 Communicating. 



Clean away the muscles, exposing the laminae of the vertebrae. Saw through the lamime of the verte- 

 bra close to the inner side of the articular processes. Divide the ligamenta subflava and remove the 

 posterior wall of the spinal canal, exposing the cord inclosed in its membranes. 



The spinal arteries are derived from : 



Vertebral arteries; 



Lateral spinal branches, 542. (532) 

 Intercostal arteries ; 



Spinal branch, 582. (571) 

 Lumbar arteries ; 



Dorsal branch, 588. (577) 

 The intraspinal veins, 668 ; Fig. 390. (654-5) 



Meningeal extra-medullary or meningo-rachidian veins: 



Anterior longitudinal spinal veins (exposed later). 

 Posterior longitudinal spinal veins. 

 The Spinal Cord, Spinal nerves, etc. 

 The spinal cord, 771. (754) 

 The dura mater, 772-3 ; Figs. 435-6. (755-6) 



Open the dural sheath by a median incision, ami expose the arachnoid. 



