back and vertebral column - pre-practical

Question 1

where does the spinal cord lie

Answer 1

in the vertebral canal

Question 2

where to the spinal nerves come out

Answer 2

intervertebral canals between the vertebrae

Question 3

where does the spinal cord end

Answer 3

as the conus medullaris

L1/2 (3 in child)

Question 4

where do the lumbar and sacral nerves come from

Answer 4

the cauda equina

Question 5

what is the filum terminal

Answer 5

pia extends and attaches to the coccyx

Question 6

where is a lumbar puncture performed

Answer 6

L3/4 or L4/5 gaps
reduced risk of damage to the spinal cord
access the dural sac/lumbar cistern for CSF

Question 7

why are there cervical and lumbar enlargements

Answer 7

for the emergence of the brachial and lumbar plexus

Question 8

spinal cord injuries

Answer 8

cervical - large vertebral canal, cord not easily injured unless considerable displacement/dislocation of the canal
thoracic - narrow vertebral canal, displacement considerable with severe cord injury
lumbar - cord extends only to L1/2, large vertebral canal, cord injury less likely in this region

Question 9

somatic NS

Answer 9

motor axon -> target neurone
one neurone, no synapses
ACh as NT

Question 10

autonomic NS

Answer 10

2 neurons, synapse in chain or ganglia
arises from spinal cord in the lateral horn 
NT varies
preganglionic - myelinated
postganglionic - unmyelinated

Question 11

sympathetic NS

Answer 11

lateral horn contains cell bodies

Question 12

where is the lateral horn present

Answer 12

T1-L2/3 (thoracolumbar outflow, sympathetic)

S2-4 (sacral outflow, parasympathetic)

Question 13

sympathetic chain

Answer 13

paravertebral paired sympathetic ganglia
on each side of the vertebral bodies from C1-S5
mass distribution mechanism for sympathetic supply to all parts of the body
T1-L2/3 and S2-4 sympathetic fibres utilise this chain to emerge at other levels

Question 14

sympathetic chain (CNS –> target)

Answer 14

1. sympathetic fibres originate in the lateral horn
2. travel in the ventral root of the spinal nerve to the mixed spinal nerve
3. leave the MSN via white ramus communicans (myelinated) as pre-ganglionic fibres to enter the sympathetic ganglion of the same vertebral level
4. after synapsing in the sympathetic chain ganglion, they re-enter the spinal nerve via the grey rc (non-myelinated) and are distributed in both dorsal and ventral rami of the spinal nerve
5. rami then go to supply the skin and body wall structures at that vertebral level (dermatome) with sympathetic input

Question 15

T10 spinal nerve

Answer 15

ventral and dorsal rami contain somatic sensory and motor fibres
both rami also contain postganglionic sympathetic fibres - arising from lateral horn cells present in spinal level T10 and have synapsed in the T10 sympathetic chain ganglion

Question 16

how to parts of the body above and below T1-L2/3 recieve sympathetic innervation

Answer 16

pre-ganglionic fibres travel up/down the sympathetic chain from between vertebral levels T1-L2/3 without synapsing there to then only synapse at the sympatheti ganglion levels higher or lower than T1-L2/3 and enter the spinal nerve occuring at that vertebral level

Question 17

what are the 3 options available in the sympathetic chain to the sympathetic fibres emerging from the lateral horn chains

Answer 17

1. synapse in the chain at the same level
2. run up/down the chain and synapse at a different level
3. pass through the chain and synapse elsewhere e.g. in the autonomic nerve plexus in the thorax/abdomen

Question 18

sympathetic fibres to the thoracic organs

Answer 18

synapse in the sympathetic chain
postganglionic fibres dont re-enter the spinal nerves but instead enter an autonomic nerve plexus out with the spinal cord which then distributes them to the target organ – splanchic nerves

Question 19

sympathetic fibres from T1-L2/3 abdominal organs

Answer 19

dont synapse in the sympathetic chain

synapse on sympathetic ganglia situated in from of the abdominal aorta - prevertebral/preaortic ganglia

Question 20

sympathetic supply to the face and head

Answer 20

superior, middle and inferior cervical ganglia are important - sympathetic fibres from T1-L2/3 synapse with these ganglia

each of the 3 ganglia are related to specific arteries in the head and neck, post-ganglionic fibres hitch-hike along these arteries to reach the target organ

Question 21

Horner’s syndrome

Answer 21

stretch/damage to the sympathetic fibres
results in symptoms when unilaterally disturbed
- partial ptosis (upper eyelid drooping)
- miosis (pupil constriction)
- anhydrosis (decreased sweating)

Question 22

autonomic sensory supply

Answer 22

body wall and organs are supplied with sympathetic motor fibres
there are some sensory fibres
nociceptive impulses from organs mainly run with the sympathetic fibres
these afferent eventually enter the dorsal root of the spinal nerve where they synapse in the dorsal root ganglion and then continue to the dorsal horn and on up to the cerebral cortex

Question 23

parasympathetic nerves

Answer 23

nerve fibres arise from the CNS with the S2,3,4, spinal nerves and 3rd, 7th, 9th (10th - vagus) cranial nerves - craniosacral outflow
S2,3,4 - pelvic splanchic nerves, supply pelvic organs, cell bodies reside in the lateral grey horn of the spinal cord (T12-L2/3 vertebral level)
preganglionic axons run through the lumbosacral plexus to the sacral foramina
preganglionic axons exit the vertebral column in the cauda equina as S2-4 spinal nerves, run through the pelvic plexus to synapse in a parasympatheti ganglion close to or in the target organ

Question 24

how many cervical vertebrae and nerves are there

Answer 24

7 vertebrae
8 nerves
C1 nerve emerges between skull and C1 vertebrae

Question 25

sentinal lymph node

Answer 25

first lymph node/ group of nodes to which cancer cells disperse

Question 26

axillary lymph nodes

Answer 26

lie along the walls of the axilla
in close association with the axillary vessels
significance in spread of breast cancer

Question 27

main lymphatic channels

Answer 27

thoracic duct - drains whole body apart from right upper quadrant
right lymphatic duct - drains only right upper quadrant

Question 28

where does the right lymphatic duct empty

Answer 28

junction of right internal jugular and right subclavian veins

Question 29

where does thoracic duct empty

Answer 29

junction of left internal jugular and subclavian veins

Question 30

cisterna chyli

Answer 30

most inferior part of the thoracic duct