Let's, first of all, look at the liver.
Shown here in this diagram is the
classical structure or description of the
structure of the liver. You can see
the liver up on the smaller component on
the top left-hand side. It has got two lobes.
It's supplied by the portal vein, and it's
drained by the vena cava. That portal vein
comes from the gut carrying all
sorts of nutrients and other products
absorbed from the gut. It's sent through
the portal vein to the liver as part of
the portal system.
And then the liver processes all those
products that are absorbed. On the right-hand
side of the diagram, you see the way in
which the hepatic lobule is described.
It's a hexagonal-shaped structure. It
consists of, firstly, in the center of
these hexagons, a central vein. That
central vein is going to take blood away
from the lobules when that blood has
secreted in it all the products that the
hepatocyte produces. And those veins will
then drain out of the liver into the
vena cava. Below, you can see a lighter
colored vein that's part of the
portal vein. When that enters the liver, it
divides into a number of branches.
And the branches of that portal vein travel
up alongside the very corners of these
hexagonal hepatic lobules. And the blood
then flows from these into the
sinusoids and into the central vein. The
hepatic artery also enters the liver and
travels up along these sides, these
borders of the hexagon, and supplies the
hepatocytes with oxygenated blood. These
hepatocytes also make bile and they are
secreted into little small bile
canaliculi, and those canaliculi
drain towards the periphery of these
lobules into bile ducts, and therefore,
they're transported away. So on the bottom
left-hand side of the diagram, you can
see these arrays of hepatocytes, sinusoids
draining blood into the central vein, and
then between these hepatocytes are thin
little bile canaliculi draining
bile back into the hepatic duct at
the periphery. And at the periphery on
the bottom left-hand side of this diagram,
you can see the portal triad.
Portal triad is the hepatic artery, portal
vein, and the hepatic duct, the bile duct.
On the right-hand side of this slide, you
can see a section through the liver.
The large structures you see are
branches of the large arteries and veins,
and perhaps, ducts. The very bulk of this
tissue though is composed of all the
hepatocytes, that's stained brown color
here. And under higher power,