hello everyone this is dr fox let's talk about
the boundaries and contents of the posterior mediastinum
in this video we'll discuss both the boundaries and contents of the posterior mediastinum
let's review the region that we're discussing so within the thoracic cavity there are three
subspaces laterally we have the pulmonary cavities which contain the lungs surrounded by the plury
medially we have the mediastinum and that mediastinum may be divided into the classic
four-part schema of superior anterior middle and posterior mediastinum or it may be divided the way
that the international thymic malignancy interest group divides it into the three-part schema we'll
be discussing the posterior mediastinum which falls into the classic anatomical four-part schema
so with the four-part schema the superior mediastinum is divided from the remainder of the
mediastinum by the thoracic plane that's the plane that begins at the sternal angle
and moves posteriorly through the intervertebral disc between t4 and t5 the remaining groups
are divisible by boundaries established by the pericardium so the heart within the pericardium
establishes that middle mediastinum anything posterior to that pericardium will be
within the posterior mediastinum now the specific boundaries of that posterior mediastinum
are going to include superiorly the thoracic plane
inferiorly the diaphragm and recall that the diaphragm has a very sharp
um convexity superiorly so um it's not just a flat plane but it's it's it's quite a a large uh hump
anteriorly the pericardium and then posteriorly the anterior edges of t5
through t12 vertebra so this is a very complex space that that we're dealing
with it's not a very big space but there are a lot of interesting visceral and neurovascular
novelties within this space so let's discuss those now so we're looking at
an image of the thoracic cavity with the lungs the pluri the heart with in the pericardium all
removed so within purple here we can get a sense for the uh the space that uh that we're discussing
and there are a few major contents that uh really should jump right out as being
visible to us uh one of them being the esophagus here and upon the esophagus
we can see all sorts of interesting branches of nerves there that would constitute the
esophageal plexus which is an autonomic plexus that that we'll discuss within this session
a major part of that esophageal plexus will be the anterior and posterior vagal trunks
so we can see the uh the anterior vagal trunk here and the posterior vagal trunk is wrapping around
here and we'll assume more of a posterior orientation uh more distal in the thoracic
esophagus these vagal trunks are uh the the continuity of the vagus nerves mixed
as they transcend the posterior mediastinum also associated with the posterior mediastinum but not
necessarily within the posterior mediastinum are going to be the sympathetic trunks specifically
the thoracic parts of the sympathetic trunks and we're speaking of ganglia t5 through t12
we discussed them in the context of the posterior mediastinum but they reside just outside
nearly right on the margins of the posterior mediastinum these are going to be adjacent
to the heads of the ribs as they articulate with the vertebral bodies and so they'll be more
lateral nevertheless they get included within this session and we'll discuss some of the branches
from these ganglia namely the splanchnic nerves the thoracic splantnic nerves to be
more specific because they will be within the posterior mediastinum but we won't be able to
see them here as they're going to be running anteriorly down the uh the bodies of the vertebrae
also within this space will be a large part of the thoracic part of the descending aorta
which we can see here and various branches coming from it both parietal branches that are serving
the walls of the the thorax and diaphragm
as well as visceral branches serving the bronchi and pericardium and mediastinal lymphatics
and esophagus and so on uh within the space will be the azigas vein that azigas vein is the uh the
main conduit for its tributaries that are draining the walls of the thorax which we'll discuss
and moving through this space as well will be the thoracic duct in various lymphatics as we'll see
here we have a an illustration that bests i think shows the aziz system i want to just point out for
you here is the profile of the diaphragm but keep in mind that uh the posterior portions of
the diaphragm are going to to come down to about that level and so uh the the purple box here is
the is the outline of the posterior mediastinum and we can see the azygos vein here in blue
ascending that and wrapping around there's the arch of the asagus which is going into
the superior vena cava and we can see two of its major tributaries the accessory hemiazygos
and the hemiazygos veins that are going to cross over and drain into the azygos
we can also see let me erase some of this the thoracic duct here in green ascending from the
cisterna kylie which is in the abdominal pelvic cavity and moving superiorly through the posterior
mediastinum more right lateral and then crossing from right to left lateral at about the superior
margin of the posterior mediastinum so around that thoracic plane and then going up to insert
into the left venous angle and then finally while we're here this gives us the opportunity to see
that those sympathetic trunks as they move through the posterior mediastinum are more adjacent to
the posterior mediastinum rather than within and those splanchnic nerves we just outline them here
are within the posterior mediastinum as they descend the posterior mediastinum to hit
pre-aortic ganglia and plexuses within the abdominal cavity
so we've discussed the boundaries of the posterior mediastinum and the contents as well as some other
structures that may not technically be contents of the posterior mediastinum but are so closely
associated that they merit discussion this is your summary slide thank you for your time