hi let's talk about the major vascular pathways of the head and neck in this video I'll provide you
with a high-level overview of the major arteries veins and lymphatics which are serving the head
neck and upper limbs so let's start with the arteries the aorta which is the major conduit
of arterial blood through the body begins is the ascending aorta which leaves the left ventricle of
the heart that ascending aorta transitions into the arch of the aorta and then the arch of the
aorta into the descending aorta that descending aorta has two parts there's the thoracic aorta
which is the aorta as it traverses the thorax and then on the other side of the diaphragm we have
the abdominal aorta which is the aorta which is found in the abdominal pelvic cavity coming
off of the arch of the aorta typically are three major branches the first being the brachiocephalic
the second being the left common carotid artery and the third being the left subclavian artery
the brachiocephalic artery is going to ascend from the superior mediastinum into the root of
the neck and there it's going to bifurcate into the right common carotid artery and the right
subclavian artery the subclavian arteries serve the upper limb the thorax and the neck as well
as parts of via the brain and spinal cord the common carotid arteries are going to bifurcate
and there's a lot of variation here typically at about the level of c3 c4 into internal carotid
arteries which will continue up to the base of the skull and they'll enter into the carotid
canal once they're inside the skull these internal carotid arteries are going to serve the contents
of the cranial cavity namely the the brain and spinal cord they'll also serve the orbit eye and
the periorbital region especially the forehead the external carotid artery is not going to enter the
skull but rather it's going to serve the the face and superficial head and also have some branches
in the neck as well now we can see that there isn't a paired brachiocephalic trunk that only
is going to serve the right side of the body the left common carotid is a direct branch of the arch
of the aorta as is the left subclavian vein and while vessels between the right and left aren't
perfectly bilaterally symmetrical we can generally assume that if the right subclavian artery has a
branch then the left subclavian artery will typically also have that branch and the same
holds true for right and left common carotid arteries so the the most we see with respect to
asymmetry from a very high level is the presence of this brachiocephalic trunk veins are a little
more symmetrical so veins are going to drain blood back to the heart specifically in this
case to the right atrium of the heart and this is very high level so coming down from the from
the cranium in in particular from the jugular foramen ah are the internal jugular veins right
and left internal jugular veins these internal veins are draining the head the the face the
cranial cavity of of the head as well as elements of the neck and they are joined by the subclavian
veins so we have a left and a right subclavian vein subclavian veins are going to drain the
structures that the subclavian arteries supply so predominantly the upper limbs but they also help
to drain the thorax and elements of the head and neck as well in the region where these veins come
together are known as the venous angles so that would be the right venous angle and this is the
left venous angle and the venous angle is the origin for the brachiocephalic veins so on the
right here we have the right brachiocephalic vein and on the left the left brachiocephalic
vein and i really want you to take notice of the asymmetry here of the the brachiocephalic veins a
lot of people will conceptualize these as sort of a simple why but that's not the case at all
the right brachiocephalic vein is a little more vertical and in line with this superior vena cava
whereas the left brachiocephalic vein is longer and more oblique so we can see that it's a much
easier straight shot into the superior vena cava from the right than it is the left brachiocephalic
vein and this left brachiocephalic vein is going to overly those arch of the aorta branches so
brachiocephalic trunk and left common carotid and left subclavian veins as well moving right
along it's important that you understand the concept of those venous angles so there's the
right venous angle and there is the left venous angle because these are going to be in important
players with respect to lymphatic drainage so the cardiovascular system is able to deliver and
then reabsorb materials at the level of capillary beds all throughout the body these capillary beds
have a myriad of forces at play but generally the movement of materials out of these capillary beds
is greater than the return of materials to these capillary beds now over a long enough period of
time even the smallest drip I can turn into a flood and so what we have as a solution is the
lymphatic system so the lymphatic system consists of lymphatic tissues and organs their specialized
capillary beds that exist that thread throughout active capillary beds of the cardiovascular system
and they absorb all of that excess interstitial fluid and they transport that fluid which is lymph
through a series of trunks these trunks have clusters of lymph nodes throughout the lymph
travels through and and as it does so antigen presenting cells can present pieces of of
pathogens to elements of the immune system T cells and and b-cells and whatnot but eventually all of
that lymph is going to drain back into venous supply at the left and right venous angles so
let's start with the the right venous angle and work our way out I think that it's probably the
the simplest thing to do here so conceptually on the right side we have the right lymphatic duct
and that right lymphatic duct is draining in the vicinity of the right Venus angle it can be on the
right on AJ you can be on the right subclavian it can be on the right brachiocephalic vein but
somewhere in there we have the the right duct that right duct is going to drain several other
ducts so accompanying the ijv is the jugular trunk accompanying the subclavian vein is the subclavian
trunk and ascending the mediastinum and helping drain the lungs is that bronco mediastinal trunk
and the three of these trunks drain into the right lymphatic duct which then drains into the vicinity
of the right venous angle here we can see all of the structures that are drained by the right
lymphatic duct so the right side of the head and neck the right upper limb and the right thorax
all have their lymph drained into the right duct this is the huge asymmetry because on the left
side we have the thoracic duct the thoracic duct drains the remainder of the body so the left head
and neck the left upper limb the left thorax and everything below the diaphragm so various trunks
are going to feed into the cisterna chyli which is that distal dilation of the thoracic duct and the
thoracic duct ascends out of the retroperitoneal space of the abdomen and it goes up through the
the thorax it ascends and sends across over from the right side to the left side at about you know
t 45 ish so that's about it the boundary of the superior mediastinum from the remainder of the
mediastinum and then it ascends on the left side and then it wraps around the the common carotid
an IJ and then it inserts into the vicinity of the left venous angle now that thoracic
duct also drains the jugular trunk on the left side the subclavian trunk on the left side and
the Bronco mediastinal trunk on the left side as well so whatever trunks exist generally on the
right those trunks also exists on the left it's just any symmetry in terms of drainage pattern of
duct that we see this asymmetry of lymphatic drainage throughout so let's let's look at a
cadaveric photograph and see what we're able to identify so we see a very long and oblique left
brachiocephalic vein here's a very distended left IJ here's the left subclavian travelling
across so there is our left venous angle and coming up out of the superior mediastinum I'll
just go a ladder to it right there it's this structure it's the thoracic duct there it is
wrapping around the common carotid artery the vagus nerve IJ and there it is inserting into
the left Venus angle the thoracic duct cadaveric lea sometimes is very tricky to distinguish from
surrounding structures um it usually looks quite Venus in nature sometimes it may have a slight
green tinge to it but more often than not it's going to look like a vein without the blood in
it so keep an eye out for for that thoracic duct especially in the in the root of the neck so let's
uh let's end with a question to to assess your understanding of what we've just discussed so
while dissecting in the lab a student noticed a long oblique venous structure crossing the
superior mediastinum when they cut through the structure they found wire leads from a pacemaker
which vessel did they dissect was it the left brachiocephalic vein the right brachiocephalic
vein the left subclavian vein the right subclavian vein or the superior vena cava so we're talking
about this peer mediastinum and I see a long oblique venous so we know that has to be a vein
vein doesn't really cut down on all of this but long and oblique certainly does that's going to
eliminate the right brachiocephalic vein the left and right subclavian veins are long but they're
not particularly oblique so that can diminish that it's purely vena cava is more vertically
oriented and that leaves us with a the left brachiocephalic vein so if you recall the
brachiocephalic veins form from the subclavian and I J the right is a little more vertically oriented
with respect to the superior vena cava whereas the left is longer and more oblique the reason
why they find pacemaker wires there as a very common place to implant a pacemaker in the left
pectoral region and those wire leads then traverse the subclavian vein the left brachiocephalic vein
and the superior vena cava on the way down into the heart thank you very much for your time