Spinal Cord and Spinal Nerves

1. Spinal Cord and Spinal Nerves

2. Spinal Cord • Enclosed in the vertebral canal, extends from the foramen magnum of the skull to the first or second lumbar vertebra where it terminates in the cone shaped conus medullaris

4. Spinal Cord • Spinal meninges; • Dura Mater – outer • Arachnoid Mater – middle • Pia Mater – inner

5. Spinal Cord • Dura Mater – composed of dense, irregular connective tissue

6. Spinal Cord • Arachnoid Mater – It is an avascular covering with a spider’s web arrangement of delicate collagen fibers and some elastic fibers

7. Spinal Cord • Pia Mater – A vascular and thin transparent connective tissue layer composed of interlacing bundles of collagen fibers and some fine elastic fibers

8. Spinal Cord • Subarachnoid space – between the arachnoid mater and pia mater which contains cerebrospinal fluid

9. Spinal Cord • The dura mater and arachnoid meningeal coverings extend beyond the conus medullaris, approximately to the level of S2

10. Spinal Cord • Filium terminale – a fibrous extension of the pia mater, extends farther and attaches to the posterior coccyx

12. Spinal Cord • 31 pairs of spinal nerves, which exit via the intervertebral foramina

13. Spinal Cord • Since the spinal cord doesn’t extend to the end of the vertebral column, the spinal nerves emerging from the inferior end must travel through the vertebral canal until reaching the appropriate intervertebral foramina

15. Spinal Cord • This collection of spinal nerves are called the cauda equina

16. Spinal Cord / Gray Matter • Looks like an H

18. Spinal Cord / Gray Matter • Posterior or dorsal horns – posterior projections

20. Spinal Cord / Gray Matter • Anterior or ventral horns – anterior projections that contain cell bodies of motor neurons

22. Spinal Cord / Gray Matter • Lateral Horns – In the thoracic and lumbar regions there is a lateral outpocketing of gray matter

24. Spinal Cord / Gray Matter • Gray commissure – central area of gray matter

26. Spinal Cord / Gray Matter • Dorsal root – Sensory fibers enter the cord here

28. Spinal Cord / Gray Matter • Dorsal Root Ganglia – Cell bodies of sensory neurons located here

30. Spinal Cord / Gray Matter • Ventral Roots – Motor neurons leave the cord here

32. Spinal Cord / Gray Matter • Spinal nerves – are formed from the fusion of the dorsal and ventral roots

33. Spinal Cord / Gray Matter Spinal Nerves; 8 pairs of cervical nerves 12 pairs of thoracic nerves 5 pairs of lumbar nerves 5 pairs of sacral nerves 1 pair of coccygeal nerves

35. Spinal Cord / White Matter • The anterior median fissure and the posterior median sulcus divide the spinal cord into R. and L. sides

37. Spinal Cord / White Matter • White matter is divided into columns; Posterior Funiculus, Anterior Funiculus, and Lateral Funiculus

39. Spinal Cord / White Matter • Each column contains distinct bundles of nerve axons called tracts

40. Spinal Cord / White Matter Two Types of Tracts 1. Sensory (ascending) tracts – conduct nerve impulses toward the brain

41. Spinal Cord / White Matter 2. Motor (descending) tracts – conduct impulses down the cord

42. Connective Tissue Coverings of Spinal Nerves • A fiber is a single axon within an endoneurium

43. Connective Tissue Coverings of Spinal Nerves • A fascicle is a bundle of fibers within a perineurium

44. Connective Tissue Coverings of Spinal Nerves • A nerve is a bundle of fascicles within an epineurium

45. Spinal Nerves and Nerve Plexus • Each nerve divides into dorsal and ventral rami

46. Spinal Nerves and Nerve Plexus • Rami contains both motor and sensory rami

47. Spinal Nerves and Nerve Plexus • Dorsal rami – serve the skin and musculture of the posterior body trunk at their approximate level of emergence

48. Spinal Nerves and Nerve Plexus • Ventral rami of spinal nerves T2 –T12 – pass anteriorly to supply the muscles of intercostal spaces, and the skin and muscles of the anterior and lateral trunk

49. Spinal Nerves and Nerve Plexus • Ventral rami of all other nerves – form complex networks of nerves called plexuses