hi let's talk about the pulmonary plexuses in this video i'll describe the basic structure of
autonomic innervation of thoracic viscera with a special emphasis on the pulmonary plexuses
this should be a nice review of what we've discussed in the previous sessions regarding
thoracic autonomics now recall there are three major types of autonomic plexus in the thorax
there are the cardiac plexuses pulmonary plexuses which we'll be focusing on in this video and the
esophageal plexus and there will be extensive communication between all of these plexuses
you're not going to see the actual plexuses in the laboratory but it's important that you understand
where they're located so that you can appreciate their anatomical relationships
especially with regards to their function now in terms of inputs into an autonomic plexus they're
going to be sympathetic and parasympathetic and in the case of the thorax the sympathetic inputs
are going to come from the sympathetic trunks and there will be both cervical sympathetic
trunk inputs as well as thoracic sympathetic trunk inputs and we'll discuss the particular
branches from individual ganglia keeping in mind that in terms of the visceral afferents
the visceral afferents that accompany the sympathetics are the visceral pain fibers
the visceral afferents that are associated with the parasympathetics which we'll get to
are associated with various autonomic feedback in reflexes
but let's step back to the sympathetics for a second recall that
within an autonomic division whether it's sympathetic or parasympathetic there will be
preganglionic and postganglionic fibers the preganglionics for both the cervical and thoracic
branches that are going to supply the thoracic viscera are going to come overwhelmingly from
white raymi communicates from t5 i'm sorry t1 through t5 and sometimes t6 so those are what
are the sympathetic outflow to the sympathetic trunk and then those fibers can descend ascend
they can go back via grey raymi communicates to the ventral primary rami of spinal nerves etc
the parasympathetic supply to thoracic viscera will come from the vagus nerves cranial nerve
10 and branches of the vagus nerves as we'll see so let's start with the sympathetic
branches the sympathetic branches supplying thoracic viscera are going to come from the
cervical sympathetic trunk which consists of superior middle and inferior ganglia
so these will all send cardiac branches i know we're talking about the pulmonary plexus but
these are cardiac branches and then there will be cardiac branches from the
second third fourth fifth and sixth thoracic ganglia that are heading to the pulmonary
plexuses as well as likely branches from t1 via the cardiac plexus which
is a minor portion of the sympathetic supply but probably there as well but we we typically think
of the sympathetic flow to the pulmonary plexuses as being t through t2 through t5 and sometimes t6
the vagus nerves and we've seen this before there will be
superior cardiac branches coming down with the vagus nerves in the carotid sheaths descending
the neck there will also be inferior cardiac branches at the the base of the neck towards the
root of the neck there are recurrent laryngeal nerves on the right side the right liquid
recurrent laryngeal nerve wraps around the right subclavian artery on the left side it
wraps around the concavity of the aorta and then these both head up to the larynx as we recall
but they will supply branches to the cardiac and pulmonary and esophageal plexuses
and then the vagus nerves once they pass the roots of the lungs and they'll pass posterior
to the roots of the lungs they're going to move from a left right orientation to an anterior
posterior orientation with the anterior vagal trunk being mostly from fibers of the left vegas
somewhat of the right and the posterior vagal trunk being mostly fibers from the right
vegas but also some from the left and we remember this with the mnemonic as you might recall larp
left goes to the anterior trunk right goes to the posterior trunk
now let's take a look at these plexuses but let's also keep in mind that these plexuses are going
to be contiguous with the cardiac plexuses so the pulmonary plexuses are distributed on the anterior
and the posterior surfaces of the roots of the lung so the anterior plexuses both left and
right are going to be relatively tiny and their input is predominantly going to come from this
superficial cardiac plexus so we're talking about cardiac branch from the superior
cervical ganglion of the sympathetic trunk and superior cardiac branches of the vagus nerves
the posterior pulmonary plexuses are posterior to the roots of the lungs so they're going to be
back there and these are going to be the bulk of the bronchial innervation probably about 80
plus of it um these are in very close association with the deep cardiac plexus and will have all of
the same inputs from it so we're talking about cardiac branches of all of the cervical ganglia
superior middle and inferior cardiac branches of thoracic ganglia t1 through t5 but for the
pulmonary plexus most of these fibers are t2 through t5 and sometimes a little bit of t6
as well as cardiac branches of the vagus nerves and branches from the recurrent laryngeal
nerves so pulmonary plexuses minor are anterior left and right major are posterior left and right
and they have many of the same inputs as the cardiac plexuses that we've already discussed
in terms of pulmonary responses to autonomic stimuli specifically the uh
the bronchi and the pulmonary vasculature um in a sympathetic response we'll have bronchodilation
so we'll have relaxation of smooth muscle you can remember this because a shot of
epinephrine an epi shot into the lateral thigh is going to lead to bronchodilation
and a sympathetic response will also lead to vasoconstriction of the pulmonary arteries because
sympathetics with all vasculature with the exception of the coronary arteries
are going to lead to vasoconstriction in terms of a parasympathetic response
we'll have bronchoconstriction and this is just the maintenance of smooth muscle tone of the
tracheobronchial tree and we'll have vasodilation of the pulmonary arteries in addition to this
there will also be respiratory responses but these aren't modulated by the pulmonary plexuses so any
increase or decrease in rate of respiration comes from the uh the the brain stem directly and and
not the uh the um the pulmonary plexuses so we've discussed the autonomic innervation of thoracic
viscera the cervical and thoracic sympathetic trunks and where they get their input from
we've also discussed the pathways and branches of the vagus nerves and the anterior and posterior
pulmonary plexuses both left and right and how they're in very strong communication with the
superficial and deep cardiac plexuses respectively this is your summary slide thank you for your time