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Spinal cord and spinal nerves lab
- 1. Spinal Cord and Spinal Nerves Lab
- 2. Spinal Cord • Spinal nerves – 31 pairs • Cervical and lumbar enlargements • Cauda equina
- 3. Figure 12.29a Cervical enlargement Dura and arachnoid mater Lumbar enlargement Conus medullaris Cauda equina Filum terminale Cervical spinal nerves Lumbar spinal nerves Sacral spinal nerves Thoracic spinal nerves (a) The spinal cord and its nerve roots, with the bony vertebral arches removed. The dura mater and arachnoid mater are cut open and reflected laterally. Spinal Cord
- 4. Cross-Sectional Anatomy • Two lengthwise grooves divide cord into right and left halves –Ventral (anterior) median fissure –Dorsal (posterior) median sulcus • Gray commissure—connects masses of gray matter; encloses central canal
- 5. Figure 12.31a (a) Cross section of spinal cord and vertebra Epidural space (contains fat) Pia mater Spinal meninges Arachnoid mater Dura mater Bone of vertebra Subdural space Subarachnoid space (contains CSF) Dorsal root ganglion Body of vertebra
- 6. Figure 12.31b (b) The spinal cord and its meningeal coverings Dorsal funiculus Dorsal median sulcus Central canal Ventral median fissure Pia mater Arachnoid mater Spinal dura mater Gray commissure Dorsal horn Gray matter Lateral horn Ventral horn Ventral funiculus Lateral funiculus White columns Dorsal root ganglion Dorsal root (fans out into dorsal rootlets) Ventral root (derived from several ventral rootlets) Spinal nerve
- 7. Gray Matter • Dorsal horns • Ventral horns • Lateral horns (only in thoracic and lumbar regions) • Dorsal root (spinal) ganglia
- 8. White Matter • Consists mostly of ascending (sensory) and descending (motor) tracts • Transverse tracts (commissural fibers) cross from one side to the other • Tracts are located in three white columns
- 9. Figure 12.33 Ascending tracts Descending tracts Fasciculus gracilis Dorsal white column Fasciculus cuneatus Dorsal spinocerebellar tract Lateral spinothalamic tract Ventral spinothalamic tract Ventral white commissure Lateral corticospinal tract Lateral reticulospinal tract Ventral corticospinal tract Medial reticulospinal tract Rubrospinal tract Vestibulospinal tract Tectospinal tract Ventral spinocerebellar tract
- 10. Spinal Nerves • 31 pairs of mixed nerves –8 cervical (C1–C8) –12 thoracic (T1–T12) –5 Lumbar (L1–L5) –5 Sacral (S1–S5) –1 Coccygeal (C0)
- 11. Figure 13.6 Cervical nerves C1 – C8 Thoracic nerves T1 – T12 Lumbar nerves L1 – L5 Sacral nerves S1 – S5 Coccygeal nerve Co1 Cervical plexus Intercostal nerves Cervical enlargement Lumbar enlargement Cauda equina Brachial plexus Lumbar plexus Sacral plexus
- 12. Spinal Nerves: Roots • Each spinal nerve connects to the spinal cord via two roots • Ventral roots –Contain motor (efferent) fibers from the ventral horn motor neurons –Fibers innervate skeletal muscles
- 13. Spinal Nerves: Roots • Dorsal roots –Contain sensory (afferent) fibers from sensory neurons in the dorsal root ganglia –Conduct impulses from peripheral receptors • Dorsal and ventral roots unite to form spinal nerves
- 14. Figure 13.7 (a) Dorsal root ganglion Gray matter White matter Ventral root Dorsal root Dorsal and ventral rootlets of spinal nerve Dorsal ramus of spinal nerve Ventral ramus of spinal nerve Sympathetic trunk ganglion Spinal nerve Rami communicantes Anterior view showing spinal cord, associated nerves, and vertebrae. The dorsal and ventral roots arise medially as rootlets and join laterally to form the spinal nerve.
- 15. Spinal Nerves: Rami • Each spinal nerve branches into mixed rami –Dorsal ramus –Larger ventral ramus –Meningeal branch –Rami communicantes (autonomic pathways) join to the ventral rami in the thoracic region
- 16. Figure 13.7 (b) Dorsal ramus Ventral ramus Intercostal nerve Spinal nerve Rami communicantes Dorsal root ganglion Dorsal root Ventral root Sympathetic trunk ganglion Sternum (b) Cross section of thorax showing the main roots and branches of a spinal nerve. Branches of intercostal nerve • Lateral cutaneous • Anterior cutaneous
- 17. Cervical Plexus • Formed by ventral rami of C1–C4 • Innervates skin and muscles of the neck, ear, back of head, and shoulders • Phrenic nerve –Major motor and sensory nerve of the diaphragm (receives fibers from C3–C5)
- 18. Figure 13.8 Hypoglossal nerve (XII) C1 C2 C3 C4 C5 Segmental branches Lesser occipital nerve Greater auricular nerve Ansa cervicalis Phrenic nerve Supraclavicular nerves Accessory nerve (XI) Transverse cervical nerve Ventral rami: Ventral rami
- 19. Brachial Plexus • Formed by ventral rami of C5–C8 and T1 (and often C4 and T2) • Major branches of this plexus: –Roots—five ventral rami (C5–T1) –Trunks—upper, middle, and lower –Divisions—anterior and posterior –Cords—lateral, medial, and posterior
- 20. Figure 13.9 (a) Upper Middle Trunks Lower Roots (ventral rami): Upper subscapular Lower subscapular Thoracodorsal Medial cutaneous nerves of the arm and forearm Long thoracic Medial pectoral Lateral pectoral Nerve to subclavius Suprascapular Dorsal scapular Posterior divisions Anterior divisions Lateral PosteriorCords Medial Axillary Musculo- cutaneous Radial Median Ulnar Posterior divisions Trunks Roots C4 C5 C6 C7 C8 T1 (a) Roots (rami C5 – T1), trunks, divisions, and cords
- 21. Brachial Plexus: Nerves • Axillary • Musculocutaneous • Median • Ulnar • Radial
- 22. Figure 13.9 (c) Median nerve Musculocutaneous nerve Radial nerve Humerus Ulna Ulnar nerve Median nerve Radius Radial nerve (superficial branch) Superficial branch of ulnar nerve Dorsal branch of ulnar nerve Digital branch of ulnar nerve Muscular branch Digital branch (c) The major nerves of the upper limb Axillary nerve Anterior divisions Posterior divisions Trunks Roots
- 23. Lumbar Plexus • Arises from L1–L4 • Innervates the thigh, abdominal wall, and psoas muscle • Femoral nerve • Obturator nerve
- 24. Figure 13.10 (a) Ventral rami and major branches of the lumbar plexus Iliohypogastric L1 L2 L3 L4 L5 Ilioinguinal Genitofemoral Lateral femoral cutaneous Obturator Femoral Lumbosacral trunk Lateral femoral cutaneous Anterior femoral cutaneous Saphenous Obturator Iliohypogastric Ilioinguinal Femoral Ventral rami Ventral rami: (b) Distribution of the major nerves from the lumbar plexus to the lower limb
- 25. Sacral Plexus • Arises from L4–S4 • Serves the buttock, lower limb, pelvic structures, and perineum • Sciatic nerve
- 26. Figure 13.11 (a) Superior gluteal Lumbosacral trunk Inferior gluteal Common fibular Tibial Posterior femoral cutaneous Pudendal Sciatic Ventral rami and major branches of the sacral plexus L4 L5 S1 S2 S3 S4 S5 Co1 Ventral rami Ventral rami:
- 27. Figure 13.11 (b) Superior gluteal Inferior gluteal Common fibular Deep fibular Superficial fibular Plantar branches Tibial Sural (cut) Posterior femoral cutaneous Pudendal Sciatic (b) Distribution of the major nerves from the sacral plexus to the lower limb