hi let's talk about veins and venous return so blood returns back to the heart via two major
veins the superior vena cava which drains blood superior to the diaphragm and the inferior vena
cava which drains blood from regions inferior to the diaphragm the superior vena cava is formed
by the Nexus of the brachiocephalic veins these brachiocephalic veins come together
in the superior mediastinum to form the superior vena cava which ends at the right atrium of the
heart each brachiocephalic vein is created by the junction of the internal jugular vein with the
subclavian vein where the internal jugular vein meets the subclavian vein we refer to this as the
venous angle and you may recall that it's in the vicinity of the venous angle where the ducts and
trunks of the lymphatic system drain there are also external jugular veins which feed into the
subclavian vein now the internal jugular veins are draining the head and neck of blood they actually
originate inside the cranium so they originated as veins that drain the brain of blood whereas
the external jugular veins are draining the the superior aspects of the inferior face and head
of blood so one misconception that people have regarding the veins is that they are symmetrical
when we look at the major veins of the thorax we can see that the superior vena cava is actually
quite linear with the right brachiocephalic vein whereas the left brachiocephalic vein is very
long and oblique so it crosses the superior mediastinum we can also see here that those
veins are formed by the junction of internal jugular with the subclavian's and we can see
some of those external jugulars but they've been pushed away because some of the muscles such as
the sternocleidomastoid have been reflected the subclavian veins receive their blood from impart
the neck in part the torso but largely from the upper limbs the drainage pattern of the upper
limbs is relatively unique and that the major veins are superficial veins and any of the deep
veins are generally just vena comitantes upper limb arteries so for instance their vena
comitantes of radial and ulnar arteries their vena comitantes of brachial arteries as well now
these superficial veins include the cephalic vein which runs along the lateral margin of the upper
limb and the basilic vein which runs along the medial margin of the upper limb these two veins
are typically joined by a median cubital vein but there is tremendous variation here and it's this
median cubital vein that's generally the target for phlebotomists so when you go to have some
blood taken or sampled a really good place for them to to sample from is that meeting cubital
vein now as the cephalic vein continues that's going to eventually drain into the axillary
vein in the Deltopectoral triangle whereas the continuation of the basilic vein is the
axillary vein when joined by the vena Comitatantes of the brachial artery so laterally we have the
cephalic medially we have the basilic and all of this drains or becomes the axillary vein that
then becomes the subclavian vein with respect to the torso the pattern of drainage is very
complex and we refer to this rather asymmetrical pattern of drainage as the azygos system now the
azygos or azygous not paired system consists of three major components there's the azygous
vein the accessory azygos vein and the hemi azygos vein the azygos vein is going to drain
posterior intercostal spaces 11 through to the first intercostal space generally drains
directly into the superior vena cava these will be on the right side the accessory hemizygous
vein typically drains intercostal spaces five through eight and then feeds into the azygos
vein the hemiazygos vein drains intercostal spaces 9 through 11 and that also drains into the
osseous vein on the left side intercostal space is 2 3 & 4 drain into the left brachiocephalic
vein and intercostal vein 1 also drains into that left brachiocephalic vein so you can see
the the pattern of drainage here of the thorax so what we would refer to as the parietal regions is
very asymmetrical here we can see the cadaveric view so the aorta has been lifted up here
so it's been retracted and pulled out of the way here we can see those posterior intercostal veins
coming together these ones are coalescing for the accessory hemizygous vein that drains into the as
igus there and these two here as well as this one is draining into the hemizygous vein which
then also drains into the the as igus as well the inferior vena cava is going to drain everything
inferior to the to the diaphragm and you're going to note a lot of branches that are very similar
to their arterial counterparts so for instance there are inferior phrenic veins these inferior
phrenic veins are either on the left side going to drain into the renal vein or the right side
they'll drain directly into the inferior vena cava there are also super renal veins again on
the left side the left super renal vein drains into the left renal vein whereas on the right
side it drains directly into the inferior vena cava a similar situation happens with the gonadal
veins the left gondal veins into the left renal vein whereas the right drains
directly into the inferior vena cava not pictured here are the lumbar veins these are just draining
the lower back in there a little posterior medial so they would their parietal branches drain into
the inferior vena cava and also not pictured here are the common iliac veins which would create the
inferior vena cava at their Nexus or coalescence there are paddock veins that drain directly into
the inferior vena cava and they are also not pictured here but they're very short and they
can the superior portion of the liver to the inferior vena cava and usually there are two
to three of these hepatic veins that are going to move between the the liver in the inferior vena
cava what is conspicuously absent are branches that would be counter to things like the celiac
trunk the superior mesenteric and the inferior mesenteric so we don't see very many of those
anterior branches having counterparts in the veins and I'll show you in a little while why that is so
here we can see the cadaveric view of the vessels here is the inferior vena cava there are the renal
veins here is the left super renal or left super anal vein here is the left renal there is the left
gonadal vein and obscured from view are the the common iliac veins those common iliac veins
are going to form from the nexus of internal iliac veins which drain the pelvic viscera and external
genitalia and perennial of blood and the external iliac veins which drain the lower limbs of blood
as well those veins come together to form the common iliac which unites to form the inferior
vena cava in terms of the lower limbs all of the deep veins are going to mirror their arteriole
counterparts there are two major superficial veins of the lower limb there's the lesser saphenous
vein that's not pictured here and the lesser saphenous vein comes from the lateral aspect
of the lower limb and that's going to drain into the popliteal vein and the great saphenous vein
the great saphenous vein ascends from just anterior to the medial malleolus and drains
into the femoral vein in the femoral triangle and finally if you recall looking at the inferior vena
cava there weren't any venous counterparts to the celiac trunk the superior mesenteric artery or the
inferior mesenteric artery and here's why that is all of the blood drained from the gastrointestinal
tract the foregut the mid gut and the hindgut goes into one of two major branches either the
superior mesenteric vein or the splenic vein and what happens is these two branches unite to form
the hepatic portal vein a portal system is when a vessel connects two beds of capillaries and so all
of the capillary beds from that gastrointestinal tract they coalesce through these veins into the
hepatic portal vein and the hepatic portal vein delivers nutrients from the GI T to the liver
for processing from there that blood is drained by the hepatic veins into the inferior vena cava
so this sets up to de-facto vena systems there's the portal system consisting of all of the veins
that drain the gastrointestinal tract into the liver and then there's the cable system
that consists of all of the other veins draining into the superior and inferior vena cava and the
connection of the liver to the cable system are those hepatic veins so we've discussed the major
pathways by which blood returns to the heart and I want you to think about those venous pathways
and correlate them to the arterial supply to those metabolically active tissues thank you you