hi let's talk about the course of the vagus nerves through the posterior mediastinum in this video
we'll discuss the courses and major branches of both vagus nerves through the thorax the stories
are going to begin higher though uh recall that the vagus nerve leaves the skull through the
jugular foramen along with the glossopharyngeal and accessory nerves so therefore nerves
IX, X, and XI all leave through the jugular foramen along with the internal jugular vein
the vagus is going to remain within the carotid sheath whereas
glossopharyngeal and accessory quickly leave the sheath at that point
also internal carotid will be bound within the carotid sheath and as we descend down
internal jugular vein vagus and common carotid will be the major constituents of that sheath
now as the vagus descends the cervical region it's going to give off two sets
of cardiac branches to the autonomics of the thorax superior cardiac branches which come
off quite high and intermingle with branches from the superior cervical ganglion of the sympathetic
trunk as well as inferior cardiac branches that are more distal in the cervical region there are
of course other branches of vagus throughout the neck but none that are relevant to the thorax
now as we get to the root of the neck we will still keep in mind that vagus is descending
within that carotid sheath and on the right side the right vagus at the root of the neck
is going to give off the right recurrent laryngeal nerve that nerve is going to head toward the
tracheo-esophageal groove up towards the larynx and it's going to give off branches to the deep
cardiac plexus as well as the pulmonary plexuses on the left side the left vagus nerve makes it
further inferior and it's giving off the left recurrent laryngeal nerve around
the level of the thoracic plane at about the concavity of the arch of the aorta both of these
vagus nerves at this point as they transition from the root of the neck to the superior mediastinum
will have an intermediate course that will take them between the arteries and
the veins in that region between the root of the neck and the superior mediastinum
so recall the right vagus nerve gives off the right recurrent laryngeal nerve at the root of
the neck that heads towards the tracheoesophageal groove um the right vagus nerve then also heads
towards that tracheoesophageal groove we can see the right recurrent laryngeal nerve there
and here is the right vagus kind of pulled away from where it uh it would naturally sit
uh the branches coming from the vagus in the superior mediastinum are going to serve the
deep cardiac plexus the pulmonary plexuses as well as the esophageal plexus it's not a
mystery that that will happen because a lot of the fibers both sympathetic and parasympathetic
are going to be held in common among the various autonomic plexuses of the thorax
here is that left vagus nerve descending through the superior mediastinum and as it transitions
more towards that thoracic plane which we can see here we can see it giving off the left recurrent
laryngeal nerve and we can see that left or current laryngeal nerve ascending out of the
superior mediastinum via that tracheoesophageal groove up towards the larynx and that left
vagus nerve from its course in the superior mediastinum will similarly give off branches
that will serve cardiac plexuses pulmonary plexuses and esophageal plexuses
it uh it bears probably repeating that these branches serving autonomic plexuses
from the vagus nerves are going to carry preganglionic parasympathetic fibers
as the vagus is a major source of preganglionic parasympathetic fibers throughout the the neck
thorax and foreign mid guts in the abdominal cavity now we are firmly within this session
these vagus nerves after they have descended from the superior mediastinum are now in the posterior
mediastinum they're going to enter the posterior mediastinum posterior to the roots of the lungs so
those main stem bronchi and pulmonary arteries and veins the vagus nerves will be posterior to those
elements the left vagus nerve is going to take more of an anterior course the right vagus nerve
which we can see a little bit of here is going to take more of a posterior course and it will have
a much more posterior course as it's more distal along the esophagus we can see the esophagus here
and it's at this point in the posterior mediastinum that the vagus nerves no longer
exist they are transformed into vagal trunks and will have an anterior and a posterior vagal trunk
that right vagus nerve is going to become the bulk of the posterior
vagal trunk that posterior trunk will include some fibers from the left vagus nerve
the left vagus nerve will become the anterior vagal trunk and that trunk will
include some fibers from the right vagus nerve so there isn't 100 fidelity between
nerves and trunks but for the most part that lovely mnemonic larp left anterior right posterior
should allow you to remember the bulk of the innervation for the vagal trunks
these trunks are going to be the dominant source of preganglionic parasympathetic fibers
to the esophageal plexus the esophageal plexus is an integral part of the gut tube conducting
materials bound for the stomach from the pharynx the anterior trunk which we can see here
is going to be a rather minor part of the parasympathetics to the foregut it will serve
some parts of the the anterior stomach as well as a portion of the the liver and hepatobiliary tree
but the dominant parasympathetic flow to the foregut and the midgut will be the posterior thigh
trunk as we'll discuss so we've discussed the uh the pathway of the vagus nerves left and right
from the jugular foramina down the neck within the carotid sheath through the root of the neck
the superior mediastinum and the posterior mediastinum we've also discussed the the major
branches to various thoracic autonomic plexuses this is your summary slide thank you for your time