hi let's talk about the azygos system in this video we'll discuss the azygos venous system
as well as the pattern of venous drainage of the right and left intercostal spaces
when we consider the venous drainage of the thorax there are two challenges that i i think
are illustrative of what evolution has really overcome the first is that we have a heart that
is going to occupy the mediastinum now when we think about that what that really means is that
in that space of the heart there is no caval access for any of the posterior intercostal veins
we have the superior and inferior vena cava draining into the right atrium of the heart
and those posterior intercostal veins have no direct access the second challenge is that the
superior vena cava within the mediastinum is going to be one of the most anteriorly oriented
pieces of vasculature and those intercostal veins are going to have their greatest drainage into the
posterior intercostal veins which would have to be conveyed through the entire depth of
the mediastinum to get to the superior vena cava so it's quite amazing what evolution and
development have overcome in order to uh to drain the thorax their solution is the azicus
system azagus comes from the root words a meaning not and zygous meaning yoke so yoked as in
two oxen being yoked together so in essence this is an unpaired system and it is not written a
so there is no u in azagus the azygos system is what conducts
the majority of blood from the walls of the thorax it's extraordinarily
variable and so we'll discuss the main patterns of drainage of the aziz system
and that main pattern is pretty straightforward we have an azygos vein which i will highlight now
circle here is that azygos vein and it's going to drain into the superior vena cava
that azygos vein drains the majority of the intercostal spaces and subcostal spaces of
the right thorax as well as regions of the lumbar with blood or of blood and then on the left side
we have an accessory hemiazigous vein which drains this region that i have
circled so the accessory hemi azagus or the aha vein and then we have the hemiazygos vein
which is going to drain the inferior portions of the thorax as well as the lumbar regions of blood
so we have the accessory and the hemiazygos veins and i always recall that accessory is superior
because a comes before h in the alphabet so let's like take a look at a little more granular detail
here to see what we can see going into the azygos vein tributary wise let's begin on the right
intercostal spaces 2 3 and 4 are going to be drained via common trunk this is the
superior intercostal vein the right superior intercostal vein and then intercostal spaces
5 through 11 as well as the subcostal vein as well as the right ascending lumbar vein
will all drain into the azygos vein but the azygos vein has two more
tributaries coming from the left side the accessory hemiazygos and the hemiazygos that
accessory hemiazygos typically drains intercostal spaces five through eight whereas the hemiazygos
is going to drain intercostal spaces nine through eleven plus subcostal plus ascending lumbar
the accessory hemiazygos and hemiazygos veins typically are going to drain directly into the
azakis vein but sometimes they may form a common trunk
and that trunk may drain into the azygos vein or you might see neither of these veins and those
posterior intercostal veins may drain directly into the azikus system either way so there are
a few non-azages tributaries and let's let's deal with them intercostal space by intercostal space
the first intercostal spaces are probably the simplest so the first intercostal spaces are
drained by the supreme intercostal veins right and left supreme intercostal veins
are going to drain the first intercostal space and they may drain either directly into their
ipsilateral that means same side brachiocephalic veins as we can see here or they may also drain
into their ipsilateral vertebral veins which the vertebral veins are going to be branches of the
subclavian veins and the one on the right might also branch directly into the superior vena cava
the second through fourth intercostal spaces are drained through the superior intercostal veins so
supreme is above the superior intercostal veins on the right side intercostal spaces two through four
are drained into the azygos specifically into the arch of the aziz vein whereas on the left side
that left superior intercostal vein is typically going to drain into the left brachiocephalic vein
and recall that that left brachiocephalic vein is very long and very oblique as it travels across
the superior mediastinum so we've discussed the challenges involved in returning blood
into the cable system within the the thorax we've discussed the pattern of venous drainage of the
thorax namely the azygos system and its major tributaries intercostal veins as well as
accessory hemiazygos and hemiazygos veins this is your summary slide thank you for your time