Anatomy of Spinal Nerves

Spinal Cord & Spinal Nerves Truly the pathway between body and mind Conducts impulses to and from the brain Carries out spinal reflexes Spinal nerves 31 pairs All are mixed nerves

Structure of the Spinal Cord Extends from the foramen magnum to the first or second lumbar vertebra. Ends in the conus medullaris Filum terminale Extends from conus medullaris to sacral vertebrae Cauda equina = filum terminale + dorsal & ventral roots from spinal nerves that extend below conus medularis Human Anatomy, 3rd edition Prentice Hall, © 2001

Coverings of the Spinal Cord 3 layers called meninges Dura mater Outer layer Arachnoid Middle layer Pia mater Adheres tightly to the surface of the spinal cord

Meninges of the Spinal Cord FG14_02.JPG Title: The Spinal Cord and Spinal Meninges Notes: (a) Anterior view of spinal cord showing meninges and spinal nerves. (b) MRI scan of inferior portion of spinal cord. (c) Posterior view of spinal cord; meningeal layers, superficial landmarks, distribution of gray and white matter. (d) Sectional view throu Keywords: spinal cord, meninges, spinal nerves, anterior median fissure, pia mater, denticulate ligaments, arachnoid mater, dura mater, cervical nerve, rami communicantes, autonomic ganglion, ventral ramus Human Anatomy, 3rd edition Prentice Hall, © 2001

Meninges of the Spinal Cord Human Anatomy, 3rd edition Prentice Hall, © 2001

Sectional Anatomy of the Spinal Cord Inner part consists of gray matter Unmyelinated cell bodies, neuroglia, & dendrites Organized into “horns” Outer part consists of white matter Tracts of myelinated fibers Ascending tracts are sensory Descending tracts are motor Human Anatomy, 3rd edition Prentice Hall, © 2001

Example of Ascending Nerve Tracts Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Spinal Nerves Connect to the spinal cord via a dorsal and a ventral root Dorsal root is sensory Contains a dorsal root ganglion Ventral root is motor Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Spinal Nerves The roots unite into the spinal nerve Spinal nerves exit through intervertebral foramen Split into branches, or rami. Dorsal ramus Ventral ramus Regions of skin supplied by a spinal nerve = dermatomes (“skin slices”) Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Dermatomes FG14_08.JPG Title: Dermatomes Notes: Anterior and posterior distribution of dermatomes; the related spinal nerves are indicated for each dermatome. Keywords: dermatomes, anterior, posterior Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Nerve Plexuses Plexus = “braid” Nerves supplying the limbs form plexuses when they leave the spinal cord Cervical plexus Brachial plexus Lumbosacral plexus Lumbar plexus Sacral plexus Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Cervical Plexus Formed by spinal nerves C1 – C5 Nerves innervate the neck and shoulder region Phrenic nerve to the diaphragm Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Brachial Plexus Formed by spinal nerves C5 – C8 and T1 Nerves innervate the arm and shoulder Radial nerve Ulnar nerve Median nerve Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Brachial Plexus FG14_11A.JPG Title: The Brachial Plexus Notes: (a) The trunks and cords of the brachial plexus. Keywords: brachial plexus, superior trunk, middle trunk, inferior trunk, medial cord, lateral cord, posterior cord, musculocutaneous, median, radial, ulnar, axillary Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Lumbosacral Plexus FG14_13C.JPG Title: The Lumbosacral Plexus, Part I Notes: (a) Anterior view of the lumbar plexus; origins and major brances. (b) Anterior view of sacral plexus; origins and major branches. (c) Anterior view of the lumbrosacral plexus and innervation of lower limb. (d) Posterior view of sacral plexus and associat Keywords: lumbosacral plexus, lumbar plexus, sacral plexus, lumbosacral trunk, iliohypogastric nerve, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator, tibial, peroneal, medial plantar, pudendal, gluteal, sciatic, saphenous Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Lumbar Plexus Formed by spinal nerves T12 and L1 – L4. Innervates the medial and anterior portions of the thigh and lower abdominal regions Lateral femoral cutaneous nerve Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Sacral Plexus Formed by spinal nerves L4 and L5, and S1 and S2 Innervates the posterior portion of the hip, thigh, and leg, and the genital region Sciatic nerve Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Sacral Plexus FG14_13B.JPG Title: The Lumbosacral Plexus, Part I Notes: (a) Anterior view of the lumbar plexus; origins and major brances. (b) Anterior view of sacral plexus; origins and major branches. (c) Anterior view of the lumbrosacral plexus and innervation of lower limb. (d) Posterior view of sacral plexus and associat Keywords: lumbosacral plexus, lumbar plexus, sacral plexus, lumbosacral trunk, iliohypogastric nerve, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator, tibial, peroneal, medial plantar, pudendal, gluteal, sciatic, saphenous Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Spinal Reflexes Reflexes are automatic responses to stimuli Spinal reflexes result from the stimulation of a spinal reflex arc. Human Anatomy, 3rd edition Prentice Hall, © 2001

Basic Elements of a Reflex Arc Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Spinal Cord Injuries Can affect sensory perception; motor paralysis Location affects severity of the injury Spinal compression results from squeezing the spinal cord within the vertebral canal Spinal transection is the severing of the spinal cord Human Anatomy, 3rd edition Prentice Hall, © 2001

Spinal Cord Injuries Quadriplegia Paraplegia http://www.apparelyzed.com/paralysis.html