About this video
Explains the structure of the liver lobule. The portal triad, made of a portal vein branch, a hepatic artery branch and a bile duct, sits around a hexagonal lobule. Blood flows through sinusoids past hepatocytes to the central vein, which drains into the hepatic vein. Oxygen comes from the artery and nutrients from the portal vein.
You'll be able to
- name the three structures of the portal triad
- trace blood flow from the portal triad through sinusoids to the central vein
- explain why hepatocytes need both nutrient-rich and oxygen-rich blood
Key words
- Portal triad
- The portal vein branch, hepatic artery branch and bile duct found around each liver lobule.
- Hepatic lobule
- The hexagonal unit of the liver built around a central vein.
- Hepatocyte
- A single liver cell that processes nutrients.
- Sinusoid
- A small vessel that carries blood from the portal triad past hepatocytes.
- Central vein
- The vessel at the centre of a lobule that collects blood before it leaves the liver.
Transcript
So we've talked about a lot of vessels here. The main three that we should focus on are these guys right here, the portal vein, the hepatic artery and the common hepatic bile duct. Together these three make what's called the portal triad. It's one of the structures that are very important to identify in surgery and also is seen very commonly in the liver, when we look at smaller cuts of the organ.
So if we were to focus in on a smaller section, like that. And blow it up so we can get a better picture of what's going on here. We can see that the liver itself, this giant fatty organ, is split up into smaller pieces or units, that are called hepatic lobules, hepatic lobules.
And in the hepatic lobule we'll have a whole bunch of our hepatocytes or single liver cells, that are hanging out, sitting around here. Surrounding these hepatocytes is going to be a representation of our portal triad. That includes a branch that was part of the portal vein.
A branch that was part of the hepatic artery and then a branch that will come together to make the common hepatic duct. So those three that make up your portal triad. Now this portal triad isn't found in just one part of the hepatic lobule. In fact, there's a bunch of them that surround the hepatocytes and make this very familiar shape, you might recall from chemistry.
So it's this six-sided ring that makes up the hepatic lobule. That has six units of the portal triad surrounding the hepatocytes. And this is how we get nutrient rich blood to enter into the hepatic lobule, so that way these hepatocytes, these liver cells, can extract nutrients for the metabolism or the storage of macro molecules.
And of course, hepatocytes are just like any other cell in the body, they need oxygen to survive. And so, oxygen will be carried in from our proper hepatic artery. So we'll supply the hepatocytes with oxygen, we'll supply them with nutrients from these branches off of the portal vein.
They're called sinusoids, I'll write that off right here. Sinusoids that come off the portal vein and finally after nutrients have been extracted, oxygens been extracted and we need to send this blood back into the hepatic vein, all of the blood will collect at this very center right here, very conveniently called the central vein.
So the central vein that sits in the very middle of our hepatic lobule, will take our nutrient and oxygen poor blood and then coalesce into a hepatic vein that'll be sent off to the heart for oxygenation by the lungs, and then passed by the intestines to receive nutrients from the absorption process we talked about.
So that's how our liver works.
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