Unique Characteristics of the Liver: Hepatic Blood Supply (Nursing)

00:00 Now, let's go back at those 2 major sources of blood supply. We already introduced you to those, so this should be familiar to you. Using a bit of repetition in your studies is the best way to encode information in your brain, and it's also kind of fun when you can look at something and say "Yeah, huh, I got that." So you see the liver. You've got the inferior vena cava. Remember that's blood draining out of the liver, into the inferior vena cava which will be returned to the right atrium of the heart. We've also got that thoracic aorta and off of that, branches, the hepatic arteries, and that fills the liver with fresh oxygenated blood. Now, up from below you've got the portal vein. Remember that's coming from the mesenteric veins that are all associated with your gut-like ____. Good. Alright, so the liver is supplied by 2 main blood vessels. You've got the aorta and the portal vein. Now, the cool part about this is we know the artery brings oxygenated blood, and that's good, but the portal vein brings 75% of the blood supply to the liver. So, be sure to write that in. Write the number 75 and the percent sign of the total blood delivered back to the liver comes from your guts via the portal vein. Okay, now that we've kind of really intensified, we've hit the blood supply to the liver, I want you to think about what happens when we start to have liver damage when we start to have liver disease. Things are going to back up into that portal vein. Right? It's going to get harder for that vein to deliver that much blood to the liver. That's where the term portal hypertension comes from. Now, when the liver becomes thick and fibrous and it's harder for that portal vein, it has to work harder to get blood through that thickened fibrous liver, that's when vessels are going to start to be enlarged and big from portal hypertension which can eventually lead to things like esophageal varices. That's what's going to put your patient at risk for severe bleeding. So we'll get to more detail about that later in the rest of our video series, but I wanted you while we are right here to keep in mind if we have damage to the liver, it's going to affect the blood supplies to the liver and that's how you end up with portal hypertension. So that established the big blood supply. Let's break it down and look at what happens in a lobule. Now, right in the center, each one of the lobules, remember you have 100,000 of them, and they're made up of little tiny cells called hepatocytes, and you've got those portal triads, the 6 groups of 3 tubes around the outside of each lobule. So we want to talk about that central vein. Remember 75% of the blood supply that's delivered to the liver comes through the mesenteric veins to the portal vein. So, that's where those blue veins on the outside are delivering blood in through to the center which is called the central vein. So, in the center of each lobule, you have the center vein, and it gets blood that's been mixed in the liver and the sinusoids, and it's returning the blood back to the heart. So the central vein is going to dump into the hepatic vein which is going to go back into the inferior vena cava and back to the right atrium. Alright, so that's the purpose of the central vein.

03:33 Remember we've got that portal vein delivering that venous blood from the gut, from the outside of the lobule, and it goes through the sinusoids and the hepatocytes into that center vein, up to the hepatic veins, then out to the inferior vena cava, and back to the heart.

03:51 Because those hepatic veins start in the liver lobule's central vein. Right? They all are linked together. This is deoxygenated blood going back to the heart.