So, this system is pretty complex. When we say a network of blood vessels, that's what it is.
We've shown you some of them here, but their job is to bring blood through the intestines,
the stomach, and the spleen and pancreas, drain it all into that portal vein, and move it on
through the liver to be processed, to be detoxified, and to choose what it's going to store,
what it's going to put back in the bloodstream, and what it's going to send to the gut to be
pooped out. We've talked in detail about what the portal vein system is but let's break down
the 4 major things that the portal blood carries. It's not just nutrients, but it's also got some
substances that have been absorbed in the intestinal mucosa or produced in the spleen.
Number 1, drugs. Now, I'm a nerd that loves pharmacology. So this is part of the first pass
effect. That's why orall drugs have to be given in larger dosages than IV drugs. Alright, so
we've got drugs are in the portal blood. The second we want to talk about is toxins from food.
So, these are things that the liver will have to help detoxify. So, so far we've talked about
drugs. We've got toxins from food. The 3rd category would be bacteria. Now, some bacteria
is great, some bacteria we'd like to get rid of. The liver is smart, and it knows what to do
with that's coming back through that portal blood. Last, we're talking about byproducts of
blood cell recycling. Okay, now I don't want to speed through this slide too quickly. So, you've
got down the blood supply to the liver, but it's really important that you think about these
4 categories; drugs, toxins, bacteria, and blood cell recycling byproducts. Because if the liver
is not functioning, if it's damaged, if it's cirrhotic, if it's fatty, we're going to have problems
with buildup of all of these substances. So we've looked at the venous and arterial blood, but I
I just wanted to remind you that blood from both the portal vein, remember coming up from
my gut into my liver, blood from both the portal vein and the hepatic artery mixes together in
the hepatic sinusoids. So, you see those portal triads, those 6 groups of 3 colored tubes all
around the hexagonal unit that we know as the lobule. You've got blood that comes up from
the portal vein, and it comes from the hepatic artery, and together it mixes in those sinusoids
that are right around the hepatocytes, those tiny little cells within the lobule. So, it mixes
together because the sinusoids are a type of capillary found in your liver, and you know in
capillaries arterial and venous blood that's where they mix. So, we've got blood coming in from
these 2 sources. It moves through the sinusoids. Right? It travels to the middle and that's
where it passes out of the lobule, it joins the hepatic vein and then drains out of the liver into
what, awesome, into the inferior vena cava on its way back to the right atrium. Well done.