hi this is dr fox let's talk about the osteology of the superior mediastinum and the root of neck
so the thorax is a bony cage that surrounds the thoracic cavity
the osteological elements include 12 thoracic vertebrae so t1 is below that line and obscured by
the remainder of the skeleton t12 is there and these vertebrae articulate with 12 pairs of ribs
so the first rib is there the second is there so on and so forth the 11th and 12th ribs are there
you'll notice that the ribs articulate with the sternum which is this osteological element here
via costal cartilages this is hyaline cartilage all but the last two ribs which we call floating
ribs now the sternum is tripartite it consists of a manubrium a body and a xiphoid process
the superior portion of the manubrium has a concavity this is called the suprasternal
notch also known as the jugular notch and that's a palpable landmark that's a useful landmark
for helping to uh to measure out the cervical region there's also
the sternal angle that's the bony angle between the manubrium which is canted posteriorly
in the body and that's going to be a very useful landmark for establishing the thoracic plane
the thoracic plane runs between that sternal angle and the intervertebral disc between t4 and t5
the portion of the mediastinum superior to the thoracic plane is the superior mediastinum
the remainder of the mediastinum so the anterior the middle and the inferior are all
inferior to i'm sorry the posterior are all inferior to the thoracic plane
now between the ribs are the intercostal spaces
because there are 12 ribs there are only 11 intercostal spaces and the intercostal spaces
are all named for the rib that is at the superior border so for instance this is rib 1 and this is
the first intercostal space rib 2 and the second intercostal space and so on and so forth down to
the 11th intercostal space below the level of the cartilage that attaches the inferior ribs to the
xiphoid process we have the costal margin or arch which is palpable do feel free to feel your own
this costal margin represents the anterior and the lateral attachment site for the diaphragm which is
the muscular division between the thoracic cavity and the abdominal pelvic cavity
which is the main engine behind ventilation and finally before we move on it's probably
worth noting that it's right about at that sternal angle that the second ribs are going to articulate
with the sternum so the second ribs are really the the first pair of truly palpable ribs
the reason being is that the first ribs are obscured from palpation
by the clavicles the clavicles colloquially called the collar bones are a part of the shoulder joint
and they are the only physical osteological joint or arthrosis between the upper limb and
the remainder of the axial skeleton the first rib is a very interesting looking rib it's very
super inferiorly compressed it's very flat especially distally towards where its
costal cartilage would attach
we can see the head of the first rib there there's the tubercle so this would be the neck
and then when we think about the root of the neck our minds should go to the anterior scalene muscle
the anterior scalene is the key to the root of the neck it's the thing that establishes all of the
relationships and the tubercle for the anterior scalene is right there that's called the scalene
tubercle that bone is raised because of the tension that the anterior scalene puts on the bone
so osteoblasts will deposit matrix under tension or pressure and as a result
a tubercle is formed now anterior to that tubercle is a groove and that groove
is for the
subclavian vein
posterior to that tubercle is another groove and that groove is for the subclavian artery and so
this is going to help you to remember the classic anatomical relationships among these structures
where at the root of the neck the subclavian vein is really encountered first it's the most
anterior structure that's probably a good thing because it offers good venous access
posterior to the subclavian vein we would have the anterior scalene muscle
riding down upon that would be the phrenic nerve entering into the superior thoracic inlet
and then posterior to that will be the subclavian artery the roots of the brachial plexus and then
we would have where the middle scalene muscle attaches and then the posterior scalene muscle
will miss the first rib entirely and attach to the second rib and then finally
ribs are going to have what are known as subcostal
or just costal grooves if we look on the inferior margin we have this slight rolling concavity
it's within this subcostal groove that we're going to find the neurovascular bundle and that
neurovascular bundle located in that groove will first consist of the intercostal vein
then the intercostal artery
and then finally
the intercostal nerve so the relative order of structures will go vein artery
nerve then going down so that's for the main intercostal bundle keeping in mind that
at the inferior margin of the intercostal space will also have the collateral bundle
and with that collateral bundle which is very small we'll have the collateral vein
collateral collateral artery and then collateral nerve so again when we look at this we'll have
nav so remember that the veins are always closest to the ribs thank you very much for your time