anatomy of spine

PMR PG Teaching

1. Anatomy of Spine -1 PMR PG Teaching- August 2016 Dr. Jimy Jose Resident, Deptt. Of PMR SMS Medical College, Jaipur

2. ANATOMY OF VERTEBRAL COLUMN Vertebral column -33 vertebrae divided into five sections seven c ervical twelve thoracic five lumbar five sacral four coccygeal vertebral body increases in size from cranial to caudal.

3. The thoracic and sacral segments maintain kyphotic postures found in utero- attachment points for the rib cage and pelvic girdle. The cervical and lumbar segments develop lordosis as erect posture is acquired.

4. A typical vertebra anterior body and a posterior arch - enclose the vertebral canal or foramen through which runs the spinal cord. The neural arch - two cylindrical pedicles laterally and two flattened laminae posteriorly which unite to form the spinous process. To either side of the arch - transverse process and superior and inferior articular processes - articulate with adjacent vertebrae to form synovial joints.

5. A typical vertebra spinous process: posteriorly and inferiorly from junction of the two laminae , it’s a site for muscle and ligament attachment . transverse process : posterolaterally from the junction of the pedicle and lamina ; site for articulation with ribs in the thoracic region. superior and inferior articular processes : Also from the region where the pedicles join the laminae ; articulate with the inferior and superior articular processes, respectively, of adjacent vertebrae.

6. articular processes : accounts for the degree of flexion, extension, or rotation possible in each segment of the vertebral column. spinous and transverse processes : levers for the numerous muscles attached to them. The length of vertebral column : averages 72 cm in men and 7 to 10 cm less in women.

7. ANATOMY OF SPINAL JOINTS vertebrae are connected by joints between the neural arches ; and between the bodies. total of six joints : The joints between the neural arches : zygapophyseal joints or facet joints. inferior articular process of one vertebra and the superior articular process of the vertebra immediately caudal. synovial joints with surfaces covered by articular cartilage, a synovial membrane, and a joint capsule enclosing them. four synovial joints (two above and two below) Interbody joints contain intervertebral discs . two symphyses (one above and one below). found throughout the vertebral column except between the first and second cervical vertebrae . The discs are designed to accommodate movement, weight bearing, and shock.

8. A typical vertebra

9. Intervertebral foramina intervertebral foramen is formed by : inferior vertebral notch on the pedicle of the vertebra above superior vertebral notch on the pedicle of the vertebra below . The foramen is bordered: posteriorly by the zygapophysial joint between the articular processes of the two vertebrae; and anteriorly by the intervertebral disc and adjacent vertebral bodies. The foramina allow structures, such as spinal nerves and blood vessels , to pass in and out of the vertebral canal. The anterior and posterior nerve roots of a spinal nerve unite within these foramina with their coverings of dura to form the segmental spinal nerves .

10. Cervical vertebrae : small size foramen transversarium in trough transverse process for the passage of the vertebral artery and veins verterbral artery passes through the transverse process of C1 to C6 , not C7 . the vertebral body is short in height , square shaped when viewed from above -- concave superior surface and a convex inferior surface spinous process is short and bifid vertebral foramen is triangular and large

11. Atypical cervical vertebrae The first , second and seventh cervical vertebrae The first and second cervical vertebrae- the atlas and axis- specialized to accommodate movement of the head. The seventh cervical vertebrae – ( vertebrae prominens ) named cos it had the longest spinous process, and its not bifid .

12. Vertebra CI (the atlas) – lacks a vertebral body or a spinous process . ring-shaped articular surfaces on its upper surface for articulation with occipital condyles ( Atlanto-occipital joints) articular surfaces on its lower surface for articulation with the axis (atlanto-axial joint) In fact, the vertebral body of CI fuses onto the body of CII during development to become the dens of CII . As a result, there is no intervertebral disc between CI and CII.

13. Atlas and axis The atlanto-occipital joint (synovial joint) allows the head to nod up and down on the vertebral column. The dens is held in position by a strong transverse ligament of atlas posterior to it and acts as a pivot that allows the atlas and attached head to rotate on the axis , side to side. The transverse processes of the atlas are large and protrude further laterally than those of the other cervical vertebrae

14. The two superolateral surfaces of the dens - attachment sites for strong alar ligaments . one on each side, which connect the dens to the medial surfaces of the occipital condyles . alar ligaments check excessive rotation of the head and atlas relative to the axis.

15. Thoracic vertebrae The twelve thoracic vertebrae – characterized by articulation with ribs. two partial facets on each side of the vertebral body--- for articulation with ribs superior costal facets- head of its own rib inferior costal facets - head of the rib below . The superior costal facet is much larger than the inferior costal facet . Each transverse process also has a facet ( transverse costal facet ) for articulation with the tubercle of its own rib . The vertebral body - heart-shaped when viewed from above vertebral foramen is circular.

16. Lumbar vertebrae distinguished by their large size The vertebral body is cylindrical vertebral foramen is triangular and larger than in the thoracic vertebrae. The transverse processes are generally thin and long, with the exception of those on vertebra LV , which are massive and cone-shaped for the attachment of iliolumbar ligaments to connect the transverse processes to the pelvic bones.

17. The sacrum The sacrum is a single bone : five fused sacral vertebrae. It is triangular in shape with the apex pointed inferiorly, and is curved concave anterior surface and convex posteriorly It articulates above with vertebra LV and below with the coccyx . It has two large L-shaped facets, one on each lateral surface, for articulation with the pelvic bones to form the sacroiliac joints The posterior surface of the sacrum has four pairs of posterior sacral foramina, anterior surface has four pairs of anterior sacral foramina for the passage of the posterior and anterior rami, respectively, of S1 to S4 spinal nerves. Sacral Promontory : anterior upper margin of first sacral vertebra- forms posterior margin of pelvi

18. Sacral canal contains- Anterior and posterior roots of sacral and coccygeal spinal nerves Filum terminale Fibrofatty material Lower part of subarachnoid space down as far as lower border of second sacral vertebra.

19. Coccyx small triangular bone - articulates with the inferior end of the sacrum represents three to four fused coccygeal vertebrae . It is characterized by its small size and by the absence of vertebral arches and therefore a vertebral canal.

20. Variations in the vertebrae C7 may possess a cervical rib Thoracic vertebrae may be increased in number by addition of the L1 vertebra which may have a rib. L5 may be incorporated into the sacrum S1 may remain partially or completely separate from sacrum and resemble a 6 th Lumbar vertebra. Coccyx which consists of four fused vertebra may have 3 or 5 vertebrae.

21. Posterior spaces between vertebral arches In most regions the laminae and spinous processes of adjacent vertebrae overlap to form a complete bony dorsal wall for the vertebral canal. in the lumbar region , large gaps exist between the posterior components of adjacent vertebral arches. become increasingly wide from vertebra LI to vertebra LV . The spaces can be widened further by flexion of the vertebral column. allow relatively easy access to the vertebral canal for clinical procedures.

22. Posterior spaces between vertebral arches

23. INTERVERTEBRAL DISC The discs are the l argest avascular structures in the body central - nucleus pulposus - semifluid mass of mucoid material . gelatinous, and absorbs compression forces between vertebrae. Peripheral - ring of anulus fibrosus 12 concentric lamellae, with alternating orientation of collagen fibers in successive lamellae to withstand multidirectional strain. Degenerative changes in anulus fibrosus - herniation of the nucleus pulposus. Posterolateral herniation : impinge on the roots of a spinal nerve in the intervertebral foramen.

24. INTERVERTEBRAL DISC

25. LIGAMENTS The anterior longitudinal ligament : anterior surfaces of the vertebral bodies base of the skull to the anterior surface of the sacrum. attached to the vertebral bodies and intervertebral discs along its length. The posterior longitudinal ligament : posterior surfaces of the vertebral bodies lines the anterior surface of the vertebral canal. attached along its length to the vertebral bodies and intervertebral discs. Tectorial membrane : The upper part of the posterior longitudinal ligament that connects CII to the intracranial aspect of the base of the skull

26. Ligamenta flava on each side, pass between the laminae of adjacent vertebrae thin, broad form part of the posterior surface of the vertebral canal. runs between the posterior surface of the lamina on the vertebra below to the anterior surface of the lamina of the vertebra above resist separation of the laminae in flexion assist in extension back to the anatomical position

27. Supraspinous ligament and ligamentum nuchae The supraspinous ligament: along the tips of the vertebral spinous processes from vertebra CVII to the sacrum From vertebra CVII to the skull, the ligament is called the ligamentum nuchae.

28. The ligamentum nuchae is a triangular, sheet-like structure in the median sagittal plane: base :attached to the skull, from the external occipital protuberance to the foramen magnum apex :attached to the tip of the spinous process of vertebra CVII the deep side of the triangle is attached to the posterior tubercle of vertebra CI and the spinous processes of the other cervical vertebrae. supports the head and resists flexion and facilitates returning the head to anatomical position.

29. Interspinous ligaments pass between adjacent vertebral spinous processes They attach from the base to the apex of each spinous process and blend with the supraspinous ligament posteriorly and the ligamenta flava anteriorly on each side.

30. ANATOMY OF SPINAL CORD AND NERVES The spinal cord is shorter than the vertebral column terminates as the conus medullaris at the L2 vertebra in adults and the L3 vertebra in neonates. From the conus, a fibrous cord called the filum terminale extends to the dorsum of the first coccygeal segment. The spinal cord has enlargements in the cervical and lumbar regions that correlate with the brachial plexus and lumbar plexus

31. The spinal cord is enclosed in three protective membranes—the pia, arachnoid, and dura mater . The pia and arachnoid membranes are separated by the subarachnoid space, which contains cerebrospinal fluid.

32. deep longitudinal fissure called the anterior median fissure in the midline anteriorly shallow furrow called the posterior median sulcus on the posterior surface posterolateral sulcus on each side of the posterior surface marks where the posterior rootlets of spinal nerves enter the cord .

33. SPINAL NERVES 31 pairs of spinal nerves attached by the anterior ( motor ) and posterior (sensory ) roots Each root is attached by a series of rootlets , which extend the whole length of the corresponding segment of the cord. Each posterior nerve root possesses a posterior/dorsal root ganglion , the cells of which give rise to peripheral and central nerve fibers.

34. Each spinal nerve divides, as it emerges from an intervertebral foramen, into two major branches: a small posterior ramus larger anterior ramus posterior rami innervate only intrinsic back muscles - anterior rami innervate most other skeletal muscles of the body, including those of the limbs and trunk. form the major somatic plexuses (cervical, brachial, lumbar, and sacral) of the body. Major visceral components of the PNS ( sympathetic trunk and prevertebral plexus).

35. Nomenclature of spinal nerves

36. Relationship Between Spinal Cord and Vertebral Segments The spinal cord has 31 segments: named according to their position with respect to associated vertebrae: ■■ 8 cervical (C) -C1 to C8 ■■ 12 thoracic (T) -T1 to T12 ■■ 5 lumbar (L)- L1 to L5 ■■ 5 sacral (S)- S1 to S5 ■■ 1 coccygeal (Co)- Co The vertebral column consists of 33 vertebrae : ■■ 7 cervical ■■ 12 thoracic ■■ 5 lumbar ■■ 5 sacral ■■ 4 coccygeal

37. Relationship of Spinal Cord Segments to Vertebral Numbers

38. The sensory component of each spinal nerve is distributed to a dermatome , a well-defined segment of the skin The first cervical and coccygeal nerves typically have no dorsal root so do not have any dermatomal representation. The skeletal musculature innervated by motor axons in a given spinal root is called a myotome .

39. Gray Matter On cross section, the gray matter is seen as an H-shaped pillar anterior and posterior gray columns, or horns, united by a thin gray commissure containing the small central canal The amount of gray matter - is related to the amount of muscle innervated at that level. size is greatest within the cervical and lumbosacral enlargements of the cord, which innervate the muscles of the upper and lower limbs , respectively

40. white matter surrounds the gray matter and is rich in nerve cell processes form large bundles or tracts that ascend and descend in the cord to other spinal cord levels or carry information to and from the brain.

41. Tracts of the Spinal Cord

42. tracts of ascending (sensory) and descending (motor) nerve fibers. Are arranged with c ervica l tracts located c entrally and thoracic, lumbar, and sacral tracts located progressively peripheral . This accounts for the clinical findings of central cord syndrome and syrinx.

43. Blood Supply of the Spinal Cord- Arteries The spinal cord receives its arterial supply from three small arteries: the two posterior spinal arteries anterior spinal artery. These longitudinally running arteries are reinforced by small segmentally arranged arteries that arise from arteries outside the vertebral column and enter the vertebral canal through the intervertebral foramina. These vessels anastomose on the surface of the cord and send branches into the substance of the white and gray matter.

44. Posterior Spinal Arteries The posterior spinal arteries arise either directly from the vertebral arteries inside the skull or indirectly from the posterior inferior cerebellar arteries. Each artery descends on the posterior surface of the spinal cord close to the posterior nerve roots and gives off branches that enter the substance of the cord. The posterior spinal arteries supply the posterior one-third of the spinal cord. The posterior spinal arteries are small in the upper thoracic region, and the first three thoracic segments of the spinal cord are particularly vulnerable to ischemia should the segmental or radicular arteries in this region be occluded.

45. Anterior Spinal Artery The anterior spinal artery is formed by the union of two arteries, each of which arises from the vertebral artery inside the skull. The anterior spinal artery then descends on the anterior surface of the spinal cord within the anterior median fissure Branches from the anterior spinal artery enter the substance of the cord and supply the anterior two-thirds of the spinal cord . In the upper and lower thoracic segments of the spinal cord, the anterior spinal artery may be extremely small. Should the segmental or radicular arteries be occluded in these regions, the fourth thoracic and the first lumbar segments of the spinal cord would be particularly liable to ischemic necrosis.

46. Segmental Spinal Arteries At each intervertebral foramen, the longitudinally running posterior and anterior spinal arteries are reinforced by small segmental arteries on both sides. The arteries are branches of arteries outside the vertebral column (deep cervical, intercostal, and lumbar arteries). Having entered the vertebral canal, each segmental spinal artery gives rise to anterior and posterior radicular arteries that accompany the anterior and posterior nerve roots to the spinal cord.

47. Additional feeder arteries enter the vertebral canal and anastomose with the anterior and posterior spinal arteries; however, the number and size of these arteries vary considerably from one individual to another. One large and important feeder artery, the great anterior medullary artery of Adamkiewicz , arises from the aorta in the lower thoracic or upper lumbar vertebral levels; it is unilateral and, in the majority of persons, enters the spinal cord from the left side. The importance of this artery lies in the fact that it may be the major source of blood to the lower two-thirds of the spinal cord.

48. Veins of the Spinal Cord The veins of the spinal cord drain into six tortuous longitudinal channels that communicate superiorly within the skull with the veins of the brain and the venous sinuses. They drain mainly into the internal vertebral venous plexus.

49. References Grays Anatomy Snell’s clinical Neuroanatomy Snell’s Anatomy

50. -Thank you