Hepatic Lobule (Nursing)

00:00 Hi, welcome to our video series on the liver. In this one, we're going to look at the lobules because they are the key to understanding liver disease. So, you see we have a picture of the liver up there for you and to remind you we've got the major artery and vein behind it as its blood supply. Now, the liver is made of 100,000 of these units we call lobules. Some things we want you to keep in mind about them is that their shape is a hexagon. That's why they're called hexagonal functional units. Each of these lobules would really have 100,000 of them in your liver. I know I keep using that number, but to me that is so impressive. So, for now, I want you to keep in mind that a lobule is one of the functional working units of the liver. You have about 100,000 of them in the liver, and I want you to pay attention to those groups of 3 that go, about six of them, around each of the units. Now, each lobule has 6 hepatic portal triads.

01:04 Okay, so what does that mean? Well, we know a lobule is hexagonal shaped, right. Now, you see there's a central vein in the middle, that's that blue circle, but if you follow out from the middle, you can count that there are 6 triads. Triad just means 3. Now, each of the triads has 1 hepatic vein, 1 hepatic artery, and 1 bile duct. Okay, so we've got the liver, 100,000 lobules.

01:37 Each lobule is shaped like a hexagon. It has a central vein in the middle, and it's got 6 hepatic portal triads. Each triad means 3, 1 hepatic vein, 1 hepatic artery, and 1 bile duct, and these are all interconnected inside your liver. Okay, so let me let that picture settle in for just a minute. I know it's pretty detailed but don't let it intimidate you because we've already given you the framework. Think back to the simple drawing of the lobule we just looked at. So, what do we know about lobules? Well, the liver has 100,000 of them. We know they're all connected.

02:17 They're shaped like a hexagon. Yeah, good. And so, we looked at this one. Yes, you can still make out that shape. Now, we've got a little cut-away in the front there, so we can show you what the middle is like, but that is definitely a hexagonal shape. Then we know there's a portal triad, so there should be 6 portal triads if it was the complete lobule, yeah, and each triad has 3 parts. You've got a bile duct. We've got a portal venule from a vein and a portal arteriole from the artery. So, we have portal triads all the way around. Now, in the middle look, there's that central vein. So, every lobule has a central vein. Now, notice how those in the portal triad, how the blue veins, look how it all is going to dump into the central vein and go up and out to the hepatic vein. So, that's one of the ways this tiny 1 lobule that's a part of 99,999 of all these other lobules that we have are connected together. So, it's hexagonal shaped.

03:26 have a portal triad at each side. We've got bile ducts, arterioles, and veins. Now, we know that the blood flows from the outside to the inside. Now, look at those little flesh-colored boxes.

03:41 Those are called sinusoids because they're surrounded by the hepatocytes. Now, hepatocytes are even smaller than lobules. So, a lobule is a group of hepatocytes, and in between them, we've got some sinusoids. They're the liver's version of capillaries. Okay, so I know that was a lot. Let's go back and review it just briefly. We've got a hexagonal shape. We have 6 portal triads. We have on each one of the portal triads we've got something for the arteries you see in red, something for the veins you see in blue, and then there's that little green guy, right, that helps us with bile. Well, blood goes from the periphery, the outside of the liver lobule, into the center and then up and out. If we're looking at the bile, it goes in the opposite direction. We'll talk a little more about that later, but I just want you to have that set in your mind when you're looking at this picture. Now, look in the upper right hand corner. That's if I reached into 1 lobule and I pulled up what we call bile canaliculi. See how much smaller that is than the big bile duct on the portal triad? Right. Those are the little tiny channels that bile travels through to get to those bile ducts. Now, these bile ducts are going to go into the hepatic ducts, then they're going to dump out of the liver, right, and join the common bile duct where the gallbladder is also attached and eventually end up in your small intestine. So, bile is made by the liver. It does phenomenal things in your body and here's the worker bees that do it. It happens right here and travels from deep inside the lobule, all the way to the outside of the bile duct to be carried outside of the liver. So, that's a much more detailed look at the liver lobule. You may want to pause for just a minute and make sure you've got that clear in your mind before you move forward with us. Alright, ready for a challenge? We talked about the flow, the direction of the flow of the blood and the bile. So, take a minute, pause the video, and I want you to draw on your own notes which way you think blood flows and which way you think bile flows. Alright, ready to check your work? Blood moves from the outside or the periphery of the lobule to the center of the lobule. So, blood flows from the outside to the inside. Now, bile flows in the opposite direction. So, we've got this network that we call bile canaliculi. So, look at that little tiny green channels that we pulled up there. That's way down deep in the meat of the lobule. That's what carries the bile through these intercellular channels to the nearest branches of the bile duct. So, bile canaliculi are just little tiny passageways that carry that bile to a bile duct in the portal triad. Now, bile is produced by the hepatocytes.

06:40 Remember those are even smaller cells that are involved in the lobule. So, bile is produced by hepatocytes, and it moves from the center of the lobule to the outside. So, blood outside in, bile inside out.