bio 210 lab instructor: dr. rebecca clarke chapter 13: the spinal cord and spinal nerves
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BIO 210 LabInstructor: Dr. Rebecca Clarke
Chapter 13: The Spinal Cord and Spinal Nerves
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Spinal CordStructurally and functionally integrated
with brainOccupies upper two-thirds of vertebral
column (adult: 1.5 ft long, 0.5 in. wide)Ends between vertebrae L1 and L2
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Figure 13-2
Gross Anatomy of the Spinal Cord
Divided into 4 regions (like vertebrae):Cervical (C)Thoracic (T)Lumbar (L)Sacral (S)
31 Pairs of spinal nervesNamed for regionsCervical numbered
for vertebra belowRest numbered for
vertebra above
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Figure 13-2
Gross Anatomy of the Spinal Cord: Distal End
Conus medullaris (medullary cone):Conical structure at T-L
junctionFilum terminale
(terminal filum):Thin strand of fibrous
tissue at end of conus medullaris
Cauda equina (“horse tail”):Bundle of elongated nerve
roots extending below conus medullaris (L2-S5)
Note: After age 4, vertebral column continues to elongate but spinal cord does not therefore roots elongate)
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Figure 13–5a
Sectional Anatomy of the Spinal Cord
Posterior median sulcus: Groove on posterior side
Anterior median fissure: Deeper, wider groove on anterior side
Gray matter covered by thick layer of white matter
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Figure 13–5a
Sectional Anatomy of the Spinal Cord: Gray Matter
Neuron cell bodies, neuroglia, unmyelinated axons
H- or butterfly-shape with horns (projections)Gray commissure – where axons connect R/L
sidesCentral canal in middle; contains CSF
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Figure 13–5a
Sectional Anatomy of the Spinal Cord: Gray Matter
Cell bodies organized in nuclei in horns of gray matter:Somatic and visceralSensory (dorsal) and motor (ventral)
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Figure 13–5a
Sectional Anatomy of the Spinal Cord: White Matter
Spinal tracts (bundles of myelinated axons) arranged in columns
Have similar distribution as nuclei in gray matterRelay same type of info (sensory or motor) in same
direction (ascending or descending) to brain
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Figure 13-2
Gross Anatomy of a Spinal Nerve
Forms 2 branches on each side of spinal cord:Dorsal root:
Contains axons of sensory (afferent) neurons coming from receptors
Ventral root:Contains axons of motor
(efferent) neurons going to effectors
Dorsal root ganglion:Contains cell bodies of
sensory neurons
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Mixed NervesCarry both sensory (afferent) and motor
(efferent) fibersSpinal nerves are mixed nerves
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Spinal Nerves and Plexuses
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Spinal Nerves and Plexuses
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Nerve PlexusComplex interwoven network of nerve
fibers of adjacent spinal nervesFormed during developmentNerves arising at a plexus:
Are mixed nerves (like spinal nerves)Control skeletal muscles of neck, upper torso,
limbs
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Figure 13–9
4 Major Nerve PlexusesCervical plexus
Neck, thoracic cavity, diaphragm
Phrenic nerveBrachial
Shoulder/pectoral girdle and upper limbs
Radial and ulnar nerves Lumbar
Pelvic girdle and lower limbs Femoral nerve
Sacral Pelvic girdle and lower limbs Sciatic nerve
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Brachial Plexus
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Meninges
Specialized, protective membranesSeparate, isolate, protect soft tissue of:
Spinal cord from bones of vertebra (spinal meninges)
Brain from bones of skull (cranial meninges)Spinal meninges continuous with cranial
meningesHave 3 layers:
Dura (“hard”) mater – outermost coveringArachnoid mater – middle layerPia (“delicate”) mater – innermost layer
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Figure 13–3
Gross Anatomy of Spinal Cord and Meninges
Spinal cord located in vertebral foramenEpidural space
Between vertebra and dura materContains loose connective tissue, blood vessels,
adipose tissueEpidural block
Injection of anestheticUsed to control pain
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Figure 13–3
Gross Anatomy of Spinal Cord and Meninges
Dura materArachnoid materSubarachnoid space
Between arachnoid membrane and pia materFilled with CSF
Acts as shock absorber Carries dissolved gases, nutrients, chemical messengers, waste
productsSpinal tap
Withdrawal of CSF for diagnostic purposes when CNS infection suspected, for back pain, headaches, disc problems, etc.
Pia mater
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MeningitisMeningitis:
Viral or bacterial infection of meninges
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Figure 16–5
Sympathetic Chain Ganglia
String of ganglia alongside spinal cord
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Sympathetic Chain Ganglia
Figure 16–4a