BIO 210 Lab

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Chapter 13 The Spinal Cord and Spinal Nerves

• BIO 210 Lab
• Instructor Dr. Rebecca Clarke

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Spinal Cord

• Structurally and functionally integrated with
  brain
• Occupies 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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Gross Anatomy of the Spinal Cord

• Divided into 4 regions (like vertebrae)
• Cervical (C)
• Thoracic (T)
• Lumbar (L)
• Sacral (S)
• 31 Pairs of spinal nerves
• Named for regions
• Cervical numbered for vertebra below
• Rest numbered for vertebra above

Figure 13-2
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Gross Anatomy of the Spinal Cord Distal End

• Conus medullaris (medullary cone)
• Conical structure at T-L junction
• Filum 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)

Figure 13-2
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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

Figure 135a
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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 sides
• Central canal in middle contains CSF

Figure 135a
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Sectional Anatomy of the Spinal Cord Gray Matter

• Cell bodies organized in nuclei in horns of gray
  matter
• Somatic and visceral
• Sensory (dorsal) and motor (ventral)

Figure 135a
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Sectional Anatomy of the Spinal Cord White
Matter

• Spinal tracts (bundles of myelinated axons)
  arranged in columns
• Have similar distribution as nuclei in gray
  matter
• Relay same type of info (sensory or motor) in
  same direction (ascending or descending) to brain

Figure 135a
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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

Figure 13-2
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Mixed Nerves

• Carry both sensory (afferent) and motor
  (efferent) fibers
• Spinal 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 Plexus

• Complex interwoven network of nerve fibers of
  adjacent spinal nerves
• Formed during development
• Nerves arising at a plexus
• Are mixed nerves (like spinal nerves)
• Control skeletal muscles of neck, upper torso,
  limbs

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4 Major Nerve Plexuses

• Cervical plexus
• ? Neck, thoracic cavity, diaphragm
• ? Phrenic nerve
• Brachial
• ? 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

Figure 139
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Brachial Plexus
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Meninges

• Specialized, protective membranes
• Separate, 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 meninges
• Have 3 layers
• Dura (hard) mater outermost covering
• Arachnoid mater middle layer
• Pia (delicate) mater innermost layer

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Gross Anatomy of Spinal Cord and Meninges

• Spinal cord located in vertebral foramen
• Epidural space
• Between vertebra and dura mater
• Contains loose connective tissue, blood vessels,
  adipose tissue
• Epidural block
• Injection of anesthetic
• Used to control pain

Figure 133
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Gross Anatomy of Spinal Cord and Meninges

• Dura mater
• Arachnoid mater
• Subarachnoid space
• Between arachnoid membrane and pia mater
• Filled with CSF
• Acts as shock absorber
• Carries dissolved gases, nutrients, chemical
  messengers, waste products
• Spinal tap
• Withdrawal of CSF for diagnostic purposes when
  CNS infection suspected, for back pain,
  headaches, disc problems, etc.
• Pia mater

Figure 133
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Meningitis

• Meningitis
• Viral or bacterial infection of meninges

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Sympathetic Chain Ganglia

• String of ganglia alongside spinal cord

Figure 165
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Sympathetic Chain Ganglia
Figure 164a