Spinal Cord Anatomy and Blood Supply.pptx

Spinal cord extends from the base of skull from the level of foramen magnum to L2 lumbar vertebra. There are 31 nerve pairings arising from it. Anterior spinal artery is the main blood supply of spinal cord mainly supplying anterior 2/3 segment. Posterior spinal artery supply posterior 1/3. Adamkiewz artery (Spina arteria magna)supplies the caudal part of spinal cord mainly below T8

1. Spinal Cord Anatomy and Blood Supply By: Dr Ebenezer, SR 1 May- 16 -2018 Moderator: Dr. Azarias

2. Outline Introduction Skeletal framework, joints, ligaments of the spinal cord Blood supply & venous drainage of the spinal cord External anatomy of the spinal cord Crossectional anatomy of the spinal cord References

3. Introduction The spinal cord is portion of the CNS inside the vertebral canal extending from foramen magnum down to the level of first and second lumbar vertebrae Cranially, it is continuous with the medulla Spinal cord is composed of 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal The spinal cord has two principal functions Impulse conduction Reflex integration A knowledge of the architecture of the spinal cord and its coverings, and of the fiber tracts and cell groups that comprise it, is essential

4. Skeletal framework, joints, ligaments

5. A typical vertebra has a body and a vertebral (neural) arch that together surround the vertebral (spinal) canal Vertebral body Pedicles Laminae Spinous process Transverse process Superior and inferior articular processes & facets Superior and inferior vertebral notches Vertebral canal

6. Cervical vertebra A typical cervical vertebra (C3–C7) has the following features: small in size, foramen transversarium , short & bifid spinous process, triangular vertebral formen . Atlas (C1) Articulates with the head ( atlanto -occipital joint), no vertebral body & spinous processs , Allows the head to nod up and down Axis (C2) Dens , a pivot that allows the atlas & head to move side to side

7. Thoracic & Lumbar vertebra Thoracic Vertebrae: superior and inferior costal facets, transverse costal facet, the vertebral body is roughly heart-shaped, vertebral foramen is circular. Lumbar vertebrae : massive and kidney shaped vertebral bodies, triangular foramen, spinous processes are short & flat

8. Sacrum and coccyx The sacrum is a single bone that represents the five fused sacral vertebrae. It has two large L-shaped facets, one on each lateral surface , for articulation with the pelvic bones. Both the posterior and anterior surface has four pairs of sacral foramina for the passage of the posterior and anterior rami , respectively, of S1 to S4 spinal nerves. Coccyx is Small triangular bone that represents 3-4 fused coccygeal vertebrae

9. Intervertebral foramina and IVD Is formed by the inferior vertebral notch on the pedicle of the vertebra above and the superior vertebral notch on the pedicle of the vertebra below. IVD: together with hyaline cartiladge , it forms symphisis b/n adjacent vertebtal bodies. Annulus fibrosus : main function is to contain the nucleus pulposus . The nucleus pulposus fills the center of IVD, is gelatinous in nature, and absorbs compression forces between vertebrae

10. Ligaments of the Spine Reinforce and support joints b/n vertebrae 1. Anterior longitudinal ligament 2. Posterior longitudinal ligament 3. Inter spinous ligament 4. Ligamentum Flava 5. Supraspinous ligament & ligamentum nuchae

11. AA supply -1. Longitudinally oriented vessels - 1.1 single anterior spinal aa union of two vessels that arise from the vertebral arteries parallel to the anterior median fissure Supplies the anterior two-third of the cord - 1.2 two posterior spinal aa Posterior branches from vertebral arteries Descend along posterolateral sulcus Supply the dorsal one-third of the cord. Spinal Cord Vascular Supply

12. -2 . Feeder arteries Asending cervical, deep cervical, posterior intercostal , lumbar & lateral sacral arteries. Are considered to be the principal blood supply to the thoracic, lumbar, sacral, and coccygeal spinal segments Some of the intercostal arteries supply segmental medullary ( radicular ) branches to the spinal cord from T1 to L1. The largest of these branches, the great ventral radicular aa , also known as the arteria radicularis magna, or artery of Adamkiewicz , enters the spinal cord between segments T9 and T12 (75%)

13. Sulcal Arteries Segmental medullary arteries unite directly with the posterior and anterior spinal arteries to form an irregular ring of arteries (an arterial corona ) with vertical connections Sulcal arteries branch from the coronal arteries at most levels Anterior sulcal arteries arise at various levels along the cervical and thoracic cord within the ventral sulcus & supply the ventral and lateral columns on either side of the spinal cord

14. Venous drainage form a number of longitudinal channels two pairs of veins on each side bracket the connections of the posterior and anterior roots to the cord; one midline channel parallels the anterior median fissure(anterior spinal vein); one midline channel passes along the posterior median sulcus (posterior spinal vein). longitudinal channels drain into an extensive plexus in epidural space of the vertebral canal, All venous drainage is ultimately into the venae cavae

15. External Anatomy of the Spinal Cord Occupies the upper two-thirds of the adult spinal canal 42 to 45 cm long in adults Conus medullaris is the conical distal (inferior) end of the spinal cord conus ends at the L1 or L2 level of the vertebral column The filum terminale extends from the tip of the conus and attaches to the distal dural sac. The filum terminale consists of pia and glial fibers and often contains a vein. Cervical enlargement and the lumbosacral enlargement

16. Approximately 30 segments 8 cervical (C), 12 thoracic (T), 5 lumbar (L), 5 sacral (S) segments, and a few small coccygeal (Co) segments—that correspond to attachments of groups of nerve roots Each spinal cord segment at lower levels is located above the similarly numbered vertebral body

17. Spinal meninges Dura, arachnoid, and the pia mater. 1. Spinal dura matter Continuous with cranial dura mater at the foramen magnum Thickest & outermost meningeal membrane Dural continuation around the filum terminale is known as the dural sac . At S2 vertebra, dura joins filum terminale to attach to the coccyx as the coccygeal ligament. Innervation is by recurrent meningeal nerves.

18. 2. Spinal arachnoid matter A loose, irregular, and trabecular layer Is continuous with cranial arachnoid mater Ends at the level of vertebra SII Separated from the pia mater by the subarachnoid space Generally avascular Surrounds the spinal cord without following the sulci .

19. 3. Spinal pia mater Firmly adheres to the surface of the spinal cord. Vascular membrane Extends into the anterior median fissure. On each side of the spinal cord, a longitudinally oriented sheet of pia mater (the denticulate ligament ) extends laterally from the cord toward the arachnoid and dura mater

20. Spinal Roots & Nerves Each of the 31 pairs of spinal nerves has a ventral root and a dorsal root( except c1) c spine, roots exit above vertebral body C8 root exits b/n vertebral bodies C7 and T1. T spine & below, the numbered roots exit below the correspondingly numbered vertebral body

21. Branches of Typical Spinal Nerves Posterior Primary Division consists of a medial branch, which is in most instances largely sensory, and a lateral branch, which is mainly motor Anterior Primary Division form the cervical, brachial, and lumbosacral plexuses. In the thoracic region they remain segmental, as intercostal nerves Rami Communicantes join the spinal nerves to the sympathetic trunk Meningeal or Recurrent Meningeal Branches/ sinuvertebral nerves carry sensory and vasomotor innervation to the meninges

22. Dermatome sensory component of each spinal nerve is distributed to a dermatome there is no C1 dermatome The dermatomes for C5, C6, C7, C8, and T1 are confined to the arm, and the C4 and T2 dermatomes are contiguous over the anterior trunk The thumb, middle finger, and fifth digit are within the C6, C7, and C8 dermatomes, respectively Nipple T4, umbilicus T10, knee L3, Anus S3

23. Myotomes myotome refers to the skeletal musculature innervated by motor axons in a given spinal root

24. Crossectional anatomy Grey matter White matter Grey commisure White commisure Central canal Anterior horn & column Posterior horn & column Lateral horn & column Anterior median fissure Posterior median sulcus Anterolateral sulcus Posterolateral sulcus

25. Cross sectional anatomy of the spinal cord Ventral horns motor neurons Dorsal horns sensory neurons Gray commissure The ventral gray column contains the cells of origin of the fibers of the ventral roots The dorsal gray column reaches almost to the posterolateral sulcus dorsolateral fasciculus ( Lissauer's tract), part of the pain pathway, lies on the periphery of the spinal cord. intermediolateral gray column (or horn in the thoracic and upper lumbar regions preganglionic cells for the autonomic nervous system

26. A cross section of the gray matter of the spinal cord shows a number of laminas (layers of nerve cells), termed Rexed's laminae or 4 parts. Anterior or ventral horn( ie , motor neurons; laminae Vlll,IX & part of VII) Posterior or dorsal horn( ie , sensory part; laminae I-VI) Intermediate zone( ie , associate neuron,lamina VII) Lateral horns( ie , part of the intermediate zone, present in the thoracic and lumbar segments, where sympathetic neurons are located).

27. Lamina I This thin marginal layer contains neurons that respond to noxious stimuli and send axons to the contralateral spinothalamic tract the dorsolateral tract of Lissauer separates this lamina from the surface of the spinal cord

28. Lamina II ( substantia gelatinosa ) consists of Golgi type II neurons, receiving fibers that carry pain and temperature sensations. this lamina is the main processing center for nociceptive (noxious) stimuli in the spinal cord. Laminae III & IV These are referred to together as the nucleus proprius . Their main input is from fibers that convey position and light touch sense .

29. Lamina V This layer contains cells that respond to both noxious and visceral afferent stimuli. Lamina VI This deepest layer of the dorsal horn contains neurons that respond to mechanical signals from joints and skin Lamina VII large zone contains the cells of the dorsal nucleus (Clarke's column) medially contains large portion of the ventral gray column. Clarke's column contains cells that give rise to the posterior spinocerebellar tract. Lamina VII also contains the intermediolateral nucleus

30. . Lamina X This represents the small neurons around the central canal or its remnants Laminas VIII and IX represent motor neuron groups in the medial and lateral portions of the ventral gray column. The medial portion (also termed the medial motor neuron column ) contains the LMNs that innervate axial musculature. The lateral motor neuron column contains LMNs for the distal muscles of the arm and leg

31. White matter Surrounds the grey matter in all sides. Contains of functionally similar axons called tracts or fasciculi,which ascend or descend in the spinal cord. Columns The spinal cord has white columns ( funiculi )- dorsal, lateral and ventral around the spinal gray columns. The dorsal column lies between the posterior median sulcus and the posterolateral sulcus. The lateral column lies between the posterolateral sulcus and the anterolateral sulcus. The ventral column lies between the anterolateral sulcus and the anterior median fissure. In the cervical and upper thoracic regions, the dorsal column is divided into a medial portion (the fasciculus gracilis ) and a lateral portion (the fasciculus cuneatus ).

32. White matter

33. Dorsal Column Tracts Fun: fine touch, proprioception & two point discrimination Impulse from: skin, joints, tendons fibers arranged in an orderly somatotopic fashion from medial to lateral.

34. Spinothalamic Tracts Anterior & Lateral Anterior Fun: Crude touch Impulse from: skin receptors axons of 2 nd ON may ascend several segments before decusation & decusate through the ventral white commissure

35. Spinothalamic Tracts Lateral Fun: conduct sharp pain, & temp. Impulse: skin receptors Afferent: terminate at the gelatinous substance of posterior horn.

36. Spinoreticular Pathway Fun: deep & chronic pain Impulse: from deep somatic structures

37. Spinocerebellar Tracts Ventral/Dorsal Ventral Fun: movement & position mechanisms Impulse from: mm spindles, Golgi tendon organs, touch & pressure receptors.

38. Spinocerebellar Tracts Dorsal Spinocerebellar tract Fun: movement & position mechanisms :it carries nonconscious sensation of mm position and tone Impulse from: mm spindles, Golgi tendon organs, touch & pressure receptors.

39. Spino-olivary tract Indirect spinocerebellar pathway ( spino - olivo - cerebellar) Fun: proprioception Impulse: from cutaneous receptors & Golgi tendon organs Axons enter cord from posterior root ganglion & terminate on second order neurons in the posterior gray column 2 nd ON cross midline & ascend as spino-olivary tract in the white matter at the junction of anterior and lateral columns to inferior olivary nuclei 3 rd ON cross midline and enter the cerebellum through inferior cerebellar peduncle

40. Descending spinal tracts The descending pathways deal with maintenance of posture and balance, control of visceral and somatic reflex activity, muscle tone, motor activity in general , and modification of the sensory signals. Descending tracts are grouped as either pyramidal or extrapyramidal.

41. Corticospinal tract Arise from cerebral cortex Lateral CST Large bundle of myelinated axons Impulse from: motor & pre motor cortex Descends through brain stem via Medullary pyramid and decussate in Pyramidal decussation into the lateral White columns (90%) Terminate in ventral gray column & base of dorsal column Fun: carry impulse that control fine motor fun.

42. Corticospinal tract Anterior CST Impulse: motor & pre motor cortex Course: descend w/o crossing in pyramids descend in anterior column decussate at segmental levels, via the anterior white commissure Terminate: anterior horn neurons, project on interneurons/LMNs of the contralateral side Fun: innervate proximal and axial mm

43. Rubrospinal Tract This fiber system arises in the contralateral red nucleus in the mid brain tegmentum and courses in the lateral white column. The tract projects to interneurons in the spinal ventral gray columns and is responsible for limb flexes.

44. Reticulospinal System T his tract arises in the reticular formation pons & medulla and descends in both the ventral and lateral white columns. Both crossed and uncrossed descending fibers are present. Terminate on dorsal and ventral horn The fibers terminating on dorsal gray column neurons are involved in modulation of sensory transmission from the body, especially pain.

45. Vestibulospinal Tracts There are two major components to the vestibulospinal tracts, medial & lateral vesibulospinal tracts. The vestibulospinal system facilitates quick movements in reaction to sudden changes in body position ( eg , falling) and provides essential control of antigravity muscles( provide excitatory input to the LMNs for extensor muscles ) in order to maintain posture. Lateral vestibulospinal tract Arise from the lateral vestibular nucleus in the brain stem and course downward, uncrossed , in the ventral white column of the spinal cord. Medial vestibulospinal tract Arise in the medial vestibular nucleus in the brain stem and descend within the cervical spinal cord, with both crossed and uncrossed components, in ventral white column to terminate at cervical levels.

46. Cont…

47. Tectospinal Tract This tract arises from the superior colliculus in the roof ( tectum ) of the midbrain and then courses in the contralateral ventral white column to provide synaptic input to ventral gray horn interneurons. Mainly terminate in the cervical segment of cord It causes head turning in response to sudden visual or auditory stimuli.

48. Cont… Descending Autonomic System Arising from the hypothalamus and brain stem , this poorly defined fiber system projects to preganglionic sympathetic neurons in the thoracolumbar spinal cord (lateral column) and to preganglionic parasympathetic neurons in sacral segments. Descending fibers in this system modulate autonomic functions, such as blood pressure, pulse and respiratory rates, and sweating. Medial Longitudinal Fasciculus This tract arises from vestibular nuclei in the brain stem. As it descends, it runs close to, and intermingles with, the tectospinal tract. terminate on ventral gray interneurons. regulate head position.

49. Spinal reflexes

50. Clinically relevant spinal reflex centers are

51. Lower- versus Upper-Motor-Neuron Lesions.

52. Questions? Or Comments

53. Reference

54. Thank you