hi let's talk about the major venous systems in this video i'll outline for you the major
systemic veins we'll discuss venipuncture and the significance of the median cubital vein
we'll talk about the great saphenous vein and we'll also talk about the hepatic portal system
so the major veins of the superior mediastinum and thorax really are a beautiful conduit
of returning blood from the head and neck upper limbs and the thorax so conceptually it's
important to understand that the superior medic vena cava is going to drain all of these areas
and it is supplied by the brachiocephalic veins also understand that the left
brachiocephalic vein is longer and more oblique than the right brachiocephalic vein and if we
look on the cadaveric image here we can see there's the superior vena cava we have a
very long and oblique left brachiocephalic vein crossing over the superior mediastinum there
these brachiocephalic veins are formed by the confluence of internal jugular veins
with subclavian veins so wherever the ijv that is returning blood from the head and neck
meet with the subclavian veins that are returning blood from the upper limb the thorax and the head
and neck the brachiocephalic vein is formed this area here where these veins come together
is known as the venous angle so there is a left and a right venous angle and these venous angles
are going to be important for lymphatics because it's within the vicinity of these venous angles
that the lymphatic ducts are going to
return lymph back into venous circulation on the left side here we'll have the thoracic duct
and on the right side we'll have the right lymphatic duct
now the uh the upper limbs are an interesting region uh in terms of venous return and i say
that because the major veins of the upper limb are superficial veins the minor veins to the upper
limb are deep veins and those deep veins are going to be venicomatantes or accompanying veins of
their respectively named arteries so for instance there are venicomatantes of radial and ulnar
of brachial arteries etc and so what we can see here is that there is a very long
cephalic vein running along the lateral aspect of the upper limb and a very long basilic vein
traveling along the medial aspect of the upper limb and there's tremendous amounts of variation
here and there is a sometimes present or i should say a frequently present vein called the
median cubital vein which represents an anastomosis between the cephalic and basilic veins
the median cubital vein is an excellent site for venipuncture so for a person
to take a blood sample veins are frequently used for venipuncture because the blood within them
is under less pressure so there's less of a risk of blood spraying everywhere and
on the upper limb they're very easy to locate now the basilic vein is going to dive deep
and it is going to come together with the brachial veins which are venicomatantes of
the brachial artery to form the axillary vein that axillary vein will traverse the axilla
and then it will become ultimately the subclavian vein which will return back to
the brachiocephalic vein the cephalic vein is going to dive deep here
in this delta pectoral triangle where it's going to meet up with the axillary vein
looking at the thorax at least the posterior wall of the thorax we can see a really interesting
venous system called the azygos system or a zygous system that would mean not
paired as you can imagine with the proliferation of viscera in the thorax
things like the heart and lungs there isn't a whole lot of room uh nor is there an opportunity
to access easily the cable system i mean we'll have a very very short very short
inferior vena cava we have a very short superior vena cava so that leaves all of this space between
with no direct access to the cable system so the solution that has evolved is this azygos system
on the right side of the thorax so keep in mind that would be right and that would be left
we have a very large and long vein called the azygos vein this azygos vein is going to drain
the right intercostal spaces generally it's draining intercostal spaces 3 down through 11 plus
the subcostal vein so these all feed into the azygos vein and the azygos vein is then draining
into the superior vena cava there are also potential connections from ascending lumbar veins
generally coming from at least the first two but sometimes the first three lumbar veins
that will drain into the azygos vein on the left side there are two vessels that are
going to drain into the azygos vein these are the accessory hemiazygos vein and the hemi azagus vein
the accessory hemiazygos vein typically is going to drain intercostal spaces five through eight
and these come together to form the accessory hemiazygos vein i'm sorry and then that
crosses the midline and feeds into the azygos vein the hemiazygos vein is from intercostal
spaces 9 through 10 and sometimes we'll also have subcostal and an ascending lumbar
and then this also is going to cross the midline and feed into the azygos
the the higher intercostal spaces so intercostal spaces one and two these can feed into either
the brachiocephalic veins or sometimes in the vicinity of the venous angle
there's a lot of variation there there's a lot of variation throughout this azygos system so if
you were to look at 10 different anatomical donors you might actually see 10 different variants here
it's just this is the the classical interpretation of the uh the azygos system
inferior to the diaphragm we have the inferior vena cava
and so here is the cross section of the inferior vena cava we have typically visceral branches
returning blood laterally parietal branches returning blood posterior laterally and sometimes
we can even have the errant anterior branch as well for viscera so let's take a look at the the
branches of the inferior vena cava let's start down here at the bottom start the very beginning
very good place to start the ivc is the coalescence of the common iliac veins
so these are draining the lower limbs and the pelvis and they come together to form
the inferior vena cava we'll also have the fourth and the third lumbar veins draining into the ivc
we can see on the right side we'll have the right gonadal vein
draining into the ivc on the left side the left gonadal drains directly into the left
renal vein the renal veins are very likely going to be the largest visceral branches
into the inferior vena cava on the right side we'll also have the right suprarenal vein
and the right inferior phrenic vein feeding into the ivc whereas on the left side the left
inferior phrenic and the left suprarenal generally form a trunk that then feeds into the
left renal vein and so this can cause issues here if there is any impingement on the
left renal vein because it bears a very close relationship to the superior mesenteric artery
and what happens if we look at this in profile let's say this were the abdominal aorta
and there is the sma that renal vein that left renal vein sits in the crook
between these two arteries and if there's any sort of aneurysm
from either of them so a abdominal aortic aneurysm that would completely compress the left renal vein
halting the blood flow from the left gonadal vein the left kidney the left suprarenal gland
as well as the left side of the diaphragm so this is known as left renal vein entrapment syndrome
and it's colloquially referred to as nutcracker syndrome
because the sma and aorta look like a nutcracker in with respect to the left renal vein so this
this asymmetry here between the uh the right and the left renal vein is very very interesting in
addition to all of these branches there's also a cluster of generally three hepatic veins
these are hard to to see because the liver is going to be in the way for a lot of the uh the
dissections but these hepatic veins are draining blood from the liver into the ivc that blood in
the liver gets there through two sources one the right and left branches of the hepatic
artery proper and two the blood from the hepatic portal system all of that blood gets returned
to cable circulation through these hepatic veins and there are generally three of them
moving right along regarding the pelvis that inferior vena cava receives
right and left common iliac
veins those common iliac veins are where the external and internal iliac veins coalesce
the internal iliac veins drain the pelvis the perineum the external genitalia if present
the external iliac veins are continuations of the femoral veins that are draining the lower limbs
when we look at the lower limbs we see a pattern that is very
similar to what we saw with the upper limbs the major veins are going to be
superficial the deep veins are venicomatantes of their associatedly named arteries
the superficial veins that we can see include the great saphenous vein the great saphenous vein
is significant largely for historical reasons but let's talk a little bit about its pathway
it is going to drain the foot and it has a very important relationship that's very
constant with the medial malleolus and you can find it just anterior to the medial malleolus
and then it's going to ascend the medial aspect of the lower limb and then it will drain into
the femoral vein in the femoral triangle it will have associated lymphatics with it
the great saphenous vein is important historically because of its constant
location people would use it as a as a means to access the vascular system for fast reperfusion
nowadays that's that's not done as often the great saphenous vein can also sometimes be harvested
for coronary artery bypass grafting the small saphenous vein also sometimes referred to as
the lesser saphenous vein is going to drain the lateral lower limb also draining the foot
this goes up the lateral aspect of the leg and if we turn to the posterior so
there's the lateral aspect and then it turns medial and it dives into the popliteal fossa
where it's going to join with deep venae comitantes to become the popliteal vein
which is an accompanying vein of the popliteal artery
moving to the portal system as we've discussed
in earlier videos we see that the length of the gastrointestinal tract from the abdominal part of
the esophagus through to the rectum all of those capillary beds drain into larger venous structures
and the three that are easiest to locate and to see include the splenic vein
which usually receives the inferior mesenteric vein but there's some variation here
there's also a superior mesenteric vein and the concept to get here is that the
union of the splenic vein with the superior mesenteric vein
forms the portal vein or the hepatic portal vein so we have it over here diagraphically
splenic vein meets superior mesenteric vein to form the portal vein or hepatic portal vein
that is then conducted to the liver and this inferior mesenteric vein
typically feeds into the splenic vein it doesn't necessarily feed into the splenic vein
sometimes you'll see it feeding into the superior mesenteric vein but look for this general pattern
the liver as i've said earlier is drained into the inferior vena cava
through the hepatic veins hepatic veins archaeal the portal vein is portal
and that leads us to our assessment question of the video and that is the venous angle
is the union of the subclavian vein with which other vein brachiocephalic vein subclavian
does touch brachiocephalic maybe external jugular vein external jugular vein although not discussed
does feed into the subclavian vein inferior vena cava um no nowhere close internal jugular vein
oh that's a that's a good one that that's ahead in my book at this point in superior vena cava
no the brachiocephalic vein is going to be in the way there so let's map out these three check marks
that we have so there's the subclavian vein there is the internal jugular vein and then there is the
brachiocephalic vein going into the superior vena cava so the angle is ijv with subclavian vein
therefore internal jugular vein is the correct answer and we care about the venous angle because
that is where lymph is returned to venous circulation thank you very much for your time