Okay.
So now we're going to take a look at the venous drainage of the abdominal organs.
So the blood doesn't return to the inferior vena cava and then into the right side of
the heart.
It actually passes through the liver, through the portal system.
So you've got this deoxygenated, nutrient-rich blood, which passes through the portal system
into a second vascular bed inside the liver and then the liver has hepatic veins, which
drains into the inferior vena cava.
So the venous drainage of the gut is through the portal system.
I'll just show you the hepatic portal vein, which is the final common pathway for the
blood of the gut.
So you can see all the veins in blue here, which are draining the gut.
They drain into this one, portal vein here.
So you can see this common pathway for this blood.
This is the portal vein.
So the portal vein splits into these two branches.
It's got a right and a left branch, which passes into the substance of the liver.
This drains into sinusoids.
And the sinusoids drain into the hepatic veins.
So you can see these two veins up here.
And these drain into the inferior vena cava just before the inferior vena cava perforates
the diaphragm.
So I'll just put the diaphragm in for reference.
You can see the hepatic veins draining into the inferior vena cava just before the IVC
passes through the diaphragm.
The important thing to know here is you've got this venous blood draining the abdominal
organs and it drains into this hepatic portal vein, which passes through a second capillary
vascular bed in the liver.
And then the liver drains via hepatic veins into the inferior vena cava.
So the blood doesn't just drain straight into the IVC.
It passes through this portal system, which passes through the liver.
So there are a few main tributaries which lead to the portal vein.
So you can see this branch coming off here, which drains into the portal vein and this
is the splenic vein.
S So I just want to orientate you a bit with
regard to the other structures in this area.
So if I just bring in the other viscera, you can see where the splenic vein lies and the
hepatic portal vein lie.
So just fading away the stomach, you can see the pancreas underneath the stomach.
The splenic vein underneath the pancreas.
So if I just fade that away, you can see the portal vein here and the splenic vein runs
along the length of the pancreas on its posterior surface.
So if I just zoom a little bit, you can see (and just fade it in a little bit more), you
can see the bile duct in front of the portal vein.
That was just to give you an idea of the relationship of these structures.
So the splenic vein and this vessel here, which is the superior mesenteric vein meet
and form the hepatic portal vein.
So the splenic vein receives various different tributaries.
So you can see there are a lot of different branches coming off the splenic vein, but
the big one here joining into the splenic vein is the inferior mesenteric vein.
And then you've got other smaller branches which come from the stomach and the pancreas
and that sort of thing.
So the superior mesenteric vein just runs alongside the superior mesenteric artery,
which you're aware of now.
So it just runs to the right of it.
It drains blood from the small intestine, the cecum, ascending colon and transverse
colon.
So the inferior mesenteric vein drains blood from the splenic flexure area, the descending
colon, the sigmoid colon and the rectum.
So the take home message is that venous drainage goes through the portal system through the
liver and then into the systemic circulation.
The portal vein receives branches from the splenic vein and the superior mesenteric vein.
It's got some other tributaries, which I'll talk about.
And then the splenic vein receives the inferior mesenteric vein.
So that's a little introduction to the blood supply to the abdominal viscera.