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Anatomy 101 > Spinal cord and spinal nerve > Flashcards

Spinal cord and spinal nerve Flashcards

1
Q

• central nervous system (CNS) consist of …

A

= brain and spinal cord

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2
Q

• peripheral nervous system

A

nerves and ganglia outside of CNS
o central role in communication between brain and rest of body
nerves and ganglia outside of CNS

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3
Q

how many pairs of cranial nerve and spinal nerves ?

A

o 12 pairs of cranial nerves and 31 pairs of spinal nerves and their ganglia

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4
Q

Spinal cord extend from …

A

foramen magnum to the 2nd lumbar vertebra

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5
Q

the spinal cord is composed of …

A

• composed of cervical, thoracic, lumbar and sacral segments named according to portion of vertebral column from which the nerves enter and exit

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6
Q

• cervical and lumbosacral enlargements

A

= associated with nerves that supply upper and lower limbs

• conus medullaris = immediately inferior to lumbosacral enlargement

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7
Q

• conus medullaris

A

immediately inferior to lumbosacral enlargement
o filum terminale = slender connective tissue extending to dorsum of coccyx
 provides longitudinal support to spinal cord

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8
Q

• cauda equine

A

= numerous roots (origins) of spinal nerves extending inferiorly from the lumbosacral enlargement and conus medullaris

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9
Q

• meninges

A

specialized membranes surrounding brain and spinal cord

o provided protection, physical stability and shock absorption

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10
Q

dura mater

location ?

A

most superficial – tough fibrous membrane

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11
Q

dura mater

type of tissue ?

A

 dense irregular connective tissue

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12
Q

dura mater :

external and internal suface covered with

A

simple squamous epithelium

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13
Q

dura mater :

caudal end

A

 caudal end blends with filum terminale

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14
Q

dura mater:

lateral extensions does what ?

A

 lateral extensions cover spinal nerve roots

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15
Q

dura mater :

attachment

A

 only attachment to bone = edges of foramen magnum of scull, 2nd and 3rd cervical vertebrae and the sacrum

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16
Q

 epidural space

A

= space between dura mater and the periosteum of the vertebral canal
• contains spinal nerve roots, blood vessels, areolar connective tissue and adipose tissue

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17
Q

• epidural anesthesia

A

(often during childbirth) = injection of anesthetics into epidural space
o needle does not penetrate dura mater and takes time for drug to diffuse to CFS
o provides mainly sensory anaesthesia
o drugs can be administered via catheter to maintain longer anesthesia

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18
Q

o arachnoid mater :
location
type of tissue ?

A

= middle layer – thin and wispy = simple squamous epithelium

 outer surface lines inner surface of dura mater

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19
Q

 subarachnoid space

location ?
contains what ?

A

space between arachnoid and pia maters

• contains cerebrospinal fluid (CSF) and blood vessels

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20
Q

clinical procedures of subarachnoid space

A

• clinical procedures introducing needle into subarachnoid space at L3/L4 or L4/L5 level
o does not puncture spinal cord because it terminals at L2 and pushes nerves aside
o spinal anesthesia (spinal block) – drug blocks action potential transmission
 advantages = delivered directly to CSF, stronger and takes effect faster

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21
Q

lumbar puncture

A

(spinal tap) (Clinical Note p.375) – CSF fluid is removed in order to examine it for infectious agents (meningitis) or blood (haemorrhage) or to measure CSF pressure

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22
Q

pia mater
location ?
fiber ?

A

= deepest layer that is bound tightly to surface of spinal cord
 contains elastic and collagen fibers and thin layer of astrocytes
 denticulate ligaments = extensions of pia mater that connect pia mater and arachnoid mater to dura mater
• help prevent side-to-side movement of spinal cord

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23
Q

white matter :

location

A

• superficial and peripherally located white matter

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24
Q

white matter ?

A

consists of myelinated and unmyelinated axons that form nerve columns (funiculi) and tracts

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25
nerve columns
funiculi
26
white matter can be divided into
columns | there is posterior white columns, anterior and lateral white columns
27
each columns contains
tracts • collection of axons within CNS (nerve = collection of axons outside CNS) • all axons within a tract relay information in the same direction • ascending tracts – carry sensory information toward the brain • descending tracts – carry motor commands from the brain to motor neurons of spinal cord
28
grey matter
contains cell bodies of glial cells and neurons, dendrites, axon terminals and unmyelinated axons
29
grey matter | how are they organized
o organized in butterfly (H-)pattern | o nuclei = clusters of nerve cell bodies in the grey matter of the central nervous system
30
grey matter : | horns
o thin dorsal (posterior) horns – contain somatic and visceral sensory nuclei o larger ventral (anterior) horns – contain somatic motor nuclei o small lateral (intermediate) horns – found only between T1 and L2 - associated with autonomic nervous system (visceral motor nuclei)
31
• anterior median fissure (crack) and posterior median sulcus (groove
) = longitudinal landmarks that partially separate two halves of spinal cord
32
• grey and white commissures
= axons that cross from one side of the spinal cord to the other
33
• central canal
contains CSF and located in the center of the grey matter | • 6-8 rootlets combine to form roots (Fig 14.2, 14.3)
34
o dorsal root
sensory (afferent) information that enters the dorsal side of the spinal cord
35
 dorsal root ganglion
swelling on dorsal root that contains the cell bodies of sensory neurons • no synapses here – axons extend into CNS and synapse with interneurons
36
o ventral root
= motor (efferent) axons that exits the ventral side of the spinal cord o extend laterally from the spinal cord o dorsal and ventral roots pass through subarachnoid space and pierce arachnoid and dura maters
37
• spinal nerve
distal to dorsal and ventral roots = combined sensory and motor fibers (mixed nerves)
38
spinal nerve contains
= axons, Schwann cells, and connective tissue (Fig 14.4) • surrounded by 3 layers of connective tissue: 1) endoneurium 2)perineurium 3 )epinuerium
39
o endoneurium
delicate loose connective tissue layer that covers each nerve fiber (and its Schwann cell sheath)  branched capillaries found between endoneurium and perineurium
40
o perineurium
heavier connective tissue layer that surrounds a bundle of axons = fascicles
41
o epineurium
o epineurium = dense irregular connective tissue that binds nerve fascicles together forming the nerve  continuous with the dura mater of the CNS
42
• 31 pairs of spinal nerves | how do they name them
o designated by a letter corresponding to the area and number corresponding to the vertebra where the nerve exits o since 1st pair of spinal nerves exit between skull and 1st cervical vertebra = C1  have eight cervical nerves but only seven cervical vertebrae o C1-C8, T1-T12, L1-L5, S1-S5, Co1) (Fig 14.7)
43
nerve of the sacrum exit where ?
• nerves of the sacrum exit through the 5 sacral foramina in the fused sacral bone
44
remaining spinal nerve exit through
• remaining spinal nerves exit through intervertebral foramina located between adjacent vertebrae
45
each spinal nerve branch into a
• each spinal nerve branches into a dorsal and ventral ramus
46
dorsal ramus
split of spinal nerve that extends dorsally  innervate most of the deep muscles of the dorsal trunk responsible for moving the vertebral column  innervates connective tissue and skin near midline of back
47
o ventral ramus
split of spinal nerve that extends ventrally  supply ventrolateral body surface, structures in body wall and limbs  thoracic region – form intercostal nerves  ventral rami of remaining spinal nerves form four major plexuses (Fig 14.7, 14.8)
48
plexus
net-like organization produced by intermingling of nerves • nerves that arise from plexuses have axons from more than one spinal nerve (from more the one level of spinal cord) • minimizes the loss of control and feeling of a specific area of the body following spinal cord injury
49
o rami communicantes
two extra branches from T1-L2 |  carry visceral motor fibers to and from autonomic ganglia of the sympathetic division of the autonomic nervous system
50
o dermatome
area of the skin supplied with sensory innervation by a pair of spinal nerves  each spinal nerve (except C1) has a specific cutaneous sensory distribution – forms dermatomal map (Fig 14.6)
51
• spinal cord injury
leading causes: automobile and motorcycle accidents, gunshot wounds, falls and swimming accidents o physical examination can pinpoint location of injury – sensory loss via evaluation of dematomes and also indicates level of motor loss
52
o spinal shock
period of time when all sensory and motor neurologic activity lost below level of injury  loss in nerve conduction due to disrupted cellular potassium ion flow  loss of function may be temporary (incomplete lesion – lasting up to a few weeks) or permanent (complete lesion)
53
o incomplete lesion
- some recovery can be expected as there is no anatomical disruption of the spinal cord  best indicator of incomplete lesion = sacral sparing • muscle movement of great toe (S1), sensory sensation in perianal area and motor control of anal sphincter (S2-S4)
54
 spinal concussion
incomplete lesion = injury caused by blow – usually due to bone or disk displacement into the cord • no visible damage to spinal cord and period of spinal shock temporary with complete recovery in few hours
55
 spinal contusion
incomplete lesion injury resulting in hemorrhage within meninges – often resulting from whiplash or falls • pressure rises in cerebrospinal fluid and white matter of cord may degenerate at site of injury • gradual recovery over period of weeks and may leave some functional loss
56
 spinal compression
incomplete lesion | spinal cord temporarily physically squeezed or distorted within vertebral canal
57
o complete lesion
 spinal laceration = tear or cut produced by vertebral fragments or foreign bodies  spinal transection = complete severing of spinal cord
58
spinal cords injuries , occurs a lot in (which area)
o most occur in the cervical region or at the thoracolumbar junction  cervical region – most severe and can result in paralysis of all four limbs (quadriplegia) with abdominal and chest muscles also affected  below T1 can result in varying degrees of paralysis of the legs (paraplegia) and abdomen
59
primary damage
damage from the mechanical event
60
o secondary damage
damage that extends from primary site due to ischemia (decreased blood flow), edema, ion imbalances, release of excitatory neurotransmitters (e.g. glutamate), and inflammatory cell invasion  main focus of current research is to limit secondary damage  major block to adult spinal cord regeneration = formation of a scar consisting of myelin and astrocytes at site of injury
61
paralysis in all four limbs
(quadriplegia)
62
• peripheral nerve palsies
= regional losses of sensory and motor function as a result of nerve trauma or compression
63
o brachial plexus birth palsy (Erb’s palsy) part of
peripheral nerve palsies nerve trauma during difficult deliveries  delivery of head but jamming of shoulder resulting in tearing of upper ventral rami or nerve roots of brachial plexus  loss of shoulder sensation and motion but preserves function of forearm and hand innervated by lower nerve roots
64
o pressure palsies
peripheral nerve palsies – mild and temporary impairment where area becomes numb  followed by paresthesia - uncomfortable “pins-and-needles” sensation  return to normal function
65
peripheral nerve palsies how many ?
• 4 major nerve plexuses: cervical, brachial, lumbar and sacral
66
• cervical plexus
ventral rami of spinal nerves from C1-C5 o deep to stenocleidomastoid muscle o innervate superficial neck structures and muscles attached to hyoid bone o phrenic nerve (C3-C5) = “keep you alive” - most important derivative of cervical plexus (mainly C4)  innervates diaphragm
67
• brachial plexus
C5-T1 – innervates pectoral girdle and upper limb | o source of five major motor nerves to upper limb
68
brachial anesthesia
entire upper limb can be anesthetized by injecting anesthetic near the brachial plexus – between the neck and shoulder posterior to the clavicle
69
 axillary nerve
innervates the deltoid and teres minor muscles | • sensory innervation to shoulder joint and skin over part of the shoulder
70
 radial nerve
innervates all the extensor muscle of the upper limb, the supinator and brachioradialis muscles • cutaneous sensory innervation to posterior portion of upper limb and posterior surface of hand
71
• radial nerve palsy
resulting from pressure on back of arm when radial nerve is compressed against the humerus
72
o crutch paralysis what kind of palsy ?
– improper use of crutches  major symptom = wrist drop - elbow, wrist, and fingers and constantly flexed radial nerve palsy
73
o Saturday night palsy what kind of palsy ?
– falling asleep on couch with arm over seat back, or beneath someone’s head radial nerve palsy
74
 musculocutaneous nerve
motor innervation to flexor muscles of arm and cutaneous innervation to part of the forearm
75
 ulnar nerve
– innervates flexor carpi ulnaris and most of intrinsic hand muscles • sensory distribution to ulnar side of hand • most easily damaged but almost always temporary = ulnar nerve palsy
76
ulnar nerve palsy
o 4th and 5th phalanges lose sensation and fingers cannot be adducted o leaning elbow on desk or banging elbow “funny bone” banged against hard object o causes painful tingling to radiate down ulnar side of forearm
77
 median nerve
– all flexor muscles of forearm and most hand muscles associated with thumb • sensory distribution to radial portion of the palm • carpal tunnel syndrome – median nerve palsy resulting in numbness, tingling and pain in fingers
78
• lumbosacral plexuses
L1-S4 = overlap of lumbar and sacral plexuses | o innervate pelvis and lower limb
79
o crural palsies
loss of sensory and motor function associated with nerves of the lumbosacral plexus
80
o lumbar plexus
L1-L4 (with a small contribution from T12)
81
 obturator nerve type of plexus ?
)– supplies adductor muscles of thigh and cutaneous distribution to medial side of thigh lumbar plexus
82
 femoral nerve type of plexus ?
innervates iliopsoas, sartorius and quadriceps femoris group • cutaneous distribution = anterior and lateral thigh and medial leg and foot lumbar plexus
83
o sacral plexus
L4-S4  pudendal nerve – innervates muscles of the perineum, urogenital diaphragm, external anal sphincter, and urethral sphincter, and sensory information from external genitalia • plays vital role in sexual stimulation • branches are anesthetized during episiotomy (cut to perineum that enlarges opening of birth canal)
84
 sciatic nerve
= largest peripheral nerve in body | • innervates biceps femoris, semimembranosus, semitendinosus and adductor magnus
85
• sciatic compression
• sciatic compression – after driving or sitting in one position for extended periods o lumbar or gluteal pain, numbness along back of leg and weakness in leg muscles
86
o sciatica
symptoms due to compression of nerve roots by distorted lumber intervertebral disc
87
what passes through greater sciatic notch in pelvis and descends in posterior thigh to the popliteal fossa where two portions separate
o tibial nerve | o common fibular nerve
88
o tibial nerve
innervates most of the flexors knee and plantar flexors of foot  sural nerve – branch that supplies cutaneous innervation over calf and plantar surface of foot  branches in foot forming medial and lateral plantar nerves
89
o common fibular nerve
– divides into deep and superficial fibular (peroneal) nerves – innervate anterior and lateral muscles of leg and foot  cutaneous distribution = lateral and anterior leg and dorsum of foot
90
 fibular palsy
sensory loss from the top of the foot and side of leg and “foot drop” -decreased ability to dorsiflex or evert foot • can occur from sitting with legs crossed

Anatomy 101 (14 decks)

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