back and vertebral column - pre-practical Flashcards
where does the spinal cord lie
in the vertebral canal
where to the spinal nerves come out
intervertebral canals between the vertebrae
where does the spinal cord end
as the conus medullaris
L1/2 (3 in child)
where do the lumbar and sacral nerves come from
the cauda equina
what is the filum terminal
pia extends and attaches to the coccyx
where is a lumbar puncture performed
L3/4 or L4/5 gaps
reduced risk of damage to the spinal cord
access the dural sac/lumbar cistern for CSF
why are there cervical and lumbar enlargements
for the emergence of the brachial and lumbar plexus
spinal cord injuries
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
somatic NS
motor axon -> target neurone
one neurone, no synapses
ACh as NT
autonomic NS
2 neurons, synapse in chain or ganglia arises from spinal cord in the lateral horn NT varies preganglionic - myelinated postganglionic - unmyelinated
sympathetic NS
lateral horn contains cell bodies
where is the lateral horn present
T1-L2/3 (thoracolumbar outflow, sympathetic)
S2-4 (sacral outflow, parasympathetic)
sympathetic chain
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
sympathetic chain (CNS –> target)
- sympathetic fibres originate in the lateral horn
- travel in the ventral root of the spinal nerve to the mixed spinal nerve
- leave the MSN via white ramus communicans (myelinated) as pre-ganglionic fibres to enter the sympathetic ganglion of the same vertebral level
- 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
- rami then go to supply the skin and body wall structures at that vertebral level (dermatome) with sympathetic input
T10 spinal nerve
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
how to parts of the body above and below T1-L2/3 recieve sympathetic innervation
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
what are the 3 options available in the sympathetic chain to the sympathetic fibres emerging from the lateral horn chains
- synapse in the chain at the same level
- run up/down the chain and synapse at a different level
- pass through the chain and synapse elsewhere e.g. in the autonomic nerve plexus in the thorax/abdomen
sympathetic fibres to the thoracic organs
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
sympathetic fibres from T1-L2/3 abdominal organs
dont synapse in the sympathetic chain
synapse on sympathetic ganglia situated in from of the abdominal aorta - prevertebral/preaortic ganglia
sympathetic supply to the face and head
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
Horner’s syndrome
stretch/damage to the sympathetic fibres results in symptoms when unilaterally disturbed - partial ptosis (upper eyelid drooping) - miosis (pupil constriction) - anhydrosis (decreased sweating)
autonomic sensory supply
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
parasympathetic nerves
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
how many cervical vertebrae and nerves are there
7 vertebrae
8 nerves
C1 nerve emerges between skull and C1 vertebrae
sentinal lymph node
first lymph node/ group of nodes to which cancer cells disperse
axillary lymph nodes
lie along the walls of the axilla
in close association with the axillary vessels
significance in spread of breast cancer
main lymphatic channels
thoracic duct - drains whole body apart from right upper quadrant
right lymphatic duct - drains only right upper quadrant
where does the right lymphatic duct empty
junction of right internal jugular and right subclavian veins
where does thoracic duct empty
junction of left internal jugular and subclavian veins
cisterna chyli
most inferior part of the thoracic duct
