hi let's talk about the mediastinum in this video we'll differentiate between the various
subdivisions of the mediastinum both of the four parts schema so the superior anterior middle
and posterior mediastinal spaces as well as the three-part schema the pre-vascular the visceral
and the pair of vertebral compartments recall that the thoracic cavity has three major spaces
laterally we have the pulmonary spaces which contain the pluri that encase the lungs and
medially we have the mediastinum which is encasing the pericardium within the
heart as well as the great vessels in other viscera and neurovasculature
that mediastinum can be conceptually divided into either four or three spaces the classic system
is for a four-part schema the newer system as of about 2017 that was produced by the international
thymic malignancy interest group has a three-part schema but let's look at each of these
so the four-part or classical division of the mediastinum involves a break between the
sternal angle the sternal angle is where the manubrium of the sternum
meets the body of the sternum you can palpate this on yourself if you feel
the the midline of your chest palpate your sternum you can feel it a definite ridge and if you can
imagine an imaginary plane that's the only way that you get an imaginary plane is to imagine it
that goes posteriorly to the intervertebral disc between t4 and t5 that's going to set a plane
now everything above that plane and below the root of the neck so that's the first rib
is going to be the superior mediastinum so that's going to be in angle or in association with
t2 through t4 vertebrae below that is the rest of the mediastinum that
sometimes people refer to as the inferior mediastinum but
no one refers to that big space like that they all call it the the individual spaces so it's
important to note that the key to this inferior space is the pericardium which is outlined
here so everything anterior to the pericardium is the anterior mediastinum everything surrounded by
the pericardium is the middle mediastinum and everything posterior to the pericardium
is the posterior mediastinum and this goes back to the bodies of the vertebrae
so we have an anterior a middle and a posterior space and the floor of these spaces
is that convex surface of the diaphragm so as we can see
the these spaces are unequal in height so the the shallowest space is the middle mediastinum
the next most is the anterior and the posterior mediastinum dips way down to the 12th thoracic
vertebrae so that that goes fairly far we can contrast this with a three-part scheme
this was developed by the international thymic malignancy interest group or itmig in 2017 they
set out to construct a schema for the mediastinum that was based off of solid multi-detector ct
technology with designated landmarks and so these are ways in which they can they can
with specific landmarks discuss the locations of various mediastinal malignancies or masses
and this is a three compartment system it's it's fairly straightforward the the superior boundary
is still rib one the inferior boundary is still the diaphragm but how they divide up that space
varies so the first compartment is the prevascular compartment and
what the boundary is is the anterior aspect of the pericardium and then you continue that
all the way up to the first rib so everything anterior to that is the prevascular compartment
so that might contain the the thymus gland everything behind that all the way back
to a boundary that is one centimeter posterior to the anterior edge of the vertebral body so
if you can imagine the vertebral bodies stacked upon one another as part of the
this part of the uh the the the bony spine here um one centimeter back from the anterior edge
of the vertebral body would look something like this so that is the posterior border
of this compartment and it's called the visceral compartment the visceral compartment
is going to contain you know the heart within the mediastinum um or within the the pericardium
it's going to contain the bronchi the the great vessels etc and now a major department from
departure from the above classification is this paravertebral compartment in the three
i'm sorry in the four part mediastinum the anterior edge of the vertebrae was really
the the end or the limit of the mediastinum but in this
system they take advantage of the space that is adjacent to the
lateral bodies of the or the lateral surfaces of the vertebral bodies so all of this space
becomes the paravertebral compartment so we have a prevascular anterior to the pericardium
we have a visceral which goes from that anterior border all the way back to one centimeter behind
the leading edge of the vertebral bodies and then we have a paravertebral compartment
that is to the side of the bodies of the
vertebrae so we've discussed the uh the two uh media style schema the classic four part system
the newer uh three compartment system this is your summary slide and thank you for your time