Chapter 13INTRODUCTIONChapter 13 The Spinal Cord & Spinal NervesSPINAL CORD ANATOMYSpinal Cord ProtectionMeningesStructures Covering the Spinal CordSlide 8ApplicationsExternal Anatomy of the Spinal CordExternal Anatomy of Spinal CordInferior End of Spinal CordSpinal tap or Lumbar PunctureSpinal nervesSpinal Cord & Spinal NervesInternal Anatomy of the Spinal CordGray Matter of the Spinal CordSlide 18White Matter of the Spinal CordSlide 20SPINAL CORD PHYSIOLOGYSensory and Motor TractsTracts of the Spinal CordLocation of Tracts inside CordFunction of Spinal TractsReflexes and Reflex ArcsReflex ArcSlide 28Stretch Reflex (patellar reflex)Illustration of the Stretch ReflexTendon ReflexIllustration of Tendon ReflexFlexor and Crossed Extensor ReflexesFlexor (withdrawal) ReflexCrossed Extensor ReflexClinical ConsiderationsSPINAL NERVESSpinal NervesConnective Tissue Covering of Spinal NervesConnective Tissue CoveringsSlide 41Branching of Spinal NerveA Nerve PlexusPlexusesCervical PlexusPhrenic NerveSlide 47Brachial PlexusBranches off Brachial PlexusSlide 50Lumbar PlexusBranches of Lumbar PlexusSlide 53Sacral PlexusBranches of Sacral PlexusSciatic Nerve BranchesDermatomesSlide 58DisordersClinical CorrelationsSlide 61Principles of Human Anatomy and Physiology, 11e 1Chapter 13The Spinal Cord & Spinal NervesLecture OutlinePrinciples of Human Anatomy and Physiology, 11e 2INTRODUCTION•The spinal cord and spinal nerves mediate reactions to environmental changes.•The spinal cord has several functions.•It processes reflexes.•It is the site for integration of EPSPs and IPSPs that arise locally or are triggered by nerve impulses from the periphery and brain.•It is a conduction pathway for sensory and motor nerve impulses.•The size of the vertebral canal varies in different regions of the vertebral column and affects spinal cord injuries.Principles of Human Anatomy and Physiology, 11e 3Chapter 13The Spinal Cord & Spinal Nerves•Together with brain forms the CNS•Functions–spinal cord reflexes–integration (summation of inhibitory and excitatory) nerve impulses–highway for upward and downward travel of sensory and motor informationPrinciples of Human Anatomy and Physiology, 11e 4SPINAL CORD ANATOMY•The spinal cord is protected by two connective tissue coverings, the meninges and vertebra, and a cushion of cerebrospinal fluid.•The vertebral column provides a bony covering of the spinal cord (Figure 13.1b).Principles of Human Anatomy and Physiology, 11e 5Spinal Cord ProtectionBy the vertebral column, meninges, cerebrospinal fluid, and vertebral ligaments.Principles of Human Anatomy and Physiology, 11e 6Meninges•The meninges are three coverings that run continuously around the spinal cord and brain (Figures 13.1a, 14.4a).–The outermost layer is the dura mater.–The middle layer is the arachnoid.–The innermost meninx is the pia mater, a thin, transparent connective tissue layer that adheres to the surface of the spinal cord and brain•Denticulate ligaments are thickenings of the pia mater that suspend the spinal cord in the middle of its dural sheath.Principles of Human Anatomy and Physiology, 11e 7Structures Covering the Spinal Cord•Vertebrae•Epidural space filled with fat•Dura mater–dense irregular CT tube•Subdural space filled with interstitial fluid•Arachnoid = spider web of collagen fibers•Subarachnoid space = CSF•Pia mater–thin layer covers BV–denticulate ligs hold in placePrinciples of Human Anatomy and Physiology, 11e 8Structures Covering the Spinal Cord•Vertebrae•Epidural space filled with fat•Dura mater–dense irregular CT tube•Subdural space filled with interstitial fluid•Arachnoid = spider web of collagen fibers•Subarachnoid space = CSF•Pia mater–thin layer covers BV–denticulate ligs hold in placePrinciples of Human Anatomy and Physiology, 11e 9Applications•The subarachnoid space is between the arachnoid mater and pia mater and contains cerebrospinal fluid (CSF).•Inflammation of the meninges is known as meningitis.•Removal of cerebrospinal fluid from the subarachnoid space is called a spinal tap (lumbar puncture). This procedure is used to diagnose pathologies and to introduce antibiotics, contrast media, anesthetics, and chemotherapeutic drugs.Principles of Human Anatomy and Physiology, 11e 10External Anatomy of the Spinal Cord•The spinal cord begins as a continuation of the medulla oblongata and terminates at about the second lumbar vertebra in an adult (Figure 13.2).–It contains cervical and lumbar enlargements that serve as points of origin for nerves to the extremities.•The tapered portion of the spinal cord is the conus medullaris, from which arise the filum terminale and cauda equina.Principles of Human Anatomy and Physiology, 11e 11External Anatomy of Spinal Cord•Flattened cylinder•16-18 Inches long & 3/4 inch diameter•In adult ends at L2•In newborn ends at L4•Growth of cord stops at age 5•Cervical enlargement–upper limbs• Lumbar enlargement–lower limbsPrinciples of Human Anatomy and Physiology, 11e 12Inferior End of Spinal Cord•Conus medullaris–cone-shaped end of spinal cord•Filum terminale–thread-like extension of pia mater–stabilizes spinal cord in canal•Caudae equinae (horse’s tail)–dorsal & ventral roots of lowest spinal nerves•Spinal segment–area of cord from which each pair of spinal nerves arisesPrinciples of Human Anatomy and Physiology, 11e 13Spinal tap or Lumbar Puncture•Technique–long needle into subarachnoid space –safe from L3 to L5•Purpose–sampling CSF for diagnosis–injection of antibiotics, anesthetics or chemotherapy–measurement of CSF pressurePrinciples of Human Anatomy and Physiology, 11e 14Spinal nerves•The 31 pairs of spinal nerves are named and numbered according to the region and level of the spinal cord from which they emerge (Figure 13.2).–8 pairs of cervical nerves, –12 pairs of thoracic nerves, –5 pairs of lumbar nerves, –5 pairs of sacral nerves, and –1 pair of coccygeal nerves.•Spinal nerves are the paths of communication between the spinal cord and most of the body.•Roots are the two points of attachment that connect each spinal nerve to a segment of the spinal cord (Figure 13.3a).Principles of Human Anatomy and Physiology, 11e 15Spinal Cord & Spinal Nerves•Spinal nerves begin as roots•Dorsal or posterior root is incoming sensory fibers–dorsal root ganglion (swelling) = cell bodies of sensory