Unique Characteristics of the Liver: Main Functions (Nursing)

by Rhonda Lawes, PhD, RN

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    00:00 So, we looked at 5 categories of the major functions of the liver. I want to share 4 more with you. The liver also stores vitamins and minerals like A, D, E, and K, B12, and copper, and iron.

    00:16 Now, we'll talk more about those later but for now, think about it being a storage center for vitamins and minerals. The liver also gives you immune system support. You got some really cool cells that are tissue macrophages called Kupffer cells and a large portion of the tissue-based macrophages hang out in your liver. Now, the liver also produces albumin, and that is a really important protein. You need that in your bloodstream to help you keep fluid in the intravascular space. Last, we're talking about how you keep your blood pressure up because the liver synthesizes angiotensinogen. Now, that's a hormone that interacts in the RAAS system. So the previous slide look at an overview of some of the main categories. Now let's break down some of the most essential ones, bile and bilirubin. Let's talk about bile production. We've already introduced this, but I just want to remind you that it's the hepatocytes that produce the bile. So the hepatocytes are the tiny little cells within the lobules, right. So, these are the little worker bees. We have cords of them in your liver, and they produce about 800 to 1,000 mL of bile a day. Okay, well, if you're not impressed, I am.

    01:34 Those are tiny little cells cranking out almost a liter of bile every day. Now, the bile really helps out the small intestine. How, you asked? Well, when that bile is produced in those tiny little hepatocytes, remember it travels from the center of the lobule to the outside of the lobule through the bile canaliculi to those little bile ducts in the portal triads, and it'll move through the liver until it drains into the main hepatic ducts, and then the main hepatic duct goes to the common bile duct which ends in the small intestine. So, that's how the liver delivers all of the bile down to the small intestine. Now, what it does in the small intestine is it helps break down and absorb things like fats, cholesterol, and some vitamins. Because what's in that small intestine, right, it's the remnants of that food that you've eaten, and you can't get what you need from that food unless you have a healthy amount of bile delivered to your small intestine. Now, what's in this icky stuff? Well, it's not real pretty looking, but it is super efficient. It has bile salts, cholesterol, bilirubin, electrolytes, and of course, water. Okay, so that's the job of bile. It's made by the hepatocytes, it's delivered to the small intestine, and it helps you get what you need from the food that you eat. Now, it also absorbs and metabolizes bilirubin. You probably know this. Well, let's just go over this pretty quickly.

    03:10 Hemoglobin is the oxygen carrier in my blood. Now, how would I know how much hemoglobin a patient has? Well, you can do that with a lab test. We call it an H&H or it can be part of a CBC (complete blood count). That tells me what the rate of percentage of hemoglobin is in my blood or the amount of oxygen-carrying ability my blood cells have. Because red blood cells can carry about 4 units of oxygen, right, but when that is done and it's dead and it's time to be broken down, bilirubin is formed. So, bile can help us absorb and metabolize the bilirubin, and when it's done, you've got the iron released. So when hemoglobin is broken down, bilirubin is formed, and iron is released. So, that iron is stored in the liver or in your bone marrow, and they can use it to make the next red blood cells. So your body is pretty efficient. When you talk about recycle, recycle, recycle, that's one of the ways the liver helps your body do it. Now, without really good, healthy, functioning liver, I can't absorb vitamin K because I need bile to absorb vitamin K, and I need vitamin K to make blood-clotting agents. So, think about through, this is why somebody with liver disease, where their liver isn't functioning right, it's all clogged up, it's thick, it's fibrous, all those little hepatocytes and lobules are kind of stiff, it's hard for them to communicate, that patient is going to be a bleeder because they can't absorb vitamin K appropriately, and you need vitamin K to make the things that help your blood clot. Now, if you take a drug called warfarin, we give that to patients who are good at making inappropriate clots like when you had a DVT, a deep vein thrombosis, in your leg, patients will go on a drug that's an anticoagulant like warfarin. Now, say that they get too much, so now they're not making clots at all. They're really, really, really a bleeder. Well, we give vitamin K as the antidote to that medication. But if a patient has liver disease, it's like they have an overdose of that medication because they don't have enough vitamin K to make clotting factors, and that's why they're really at risk for bleeding. Because if the liver can't produce enough bile, there won't be enough clotting factors, and that patient is in increased risk for bleeding. So, if they fall, what if they bumped their head, they have an increased risk to have a bleed in their head or they're going to bruise really easily. So when you're caring for liver patients, you'll notice that it doesn't take very much for them to develop a bruise, and they'll likely have several bruises over their body, and they won't even be able to remember what caused it. So, the liver, it's very important in vitamin K absorption. Without vitamin K, it can't make the clotting factors it needs, and your patient is at risk for increased bleeding. So we talked about bile and vitamin K and its role in clotting. Now, let's talk about bile and fat metabolization. Fat is metabolized by bile. That's what helps make it easier to digest for your body. Now, it also metabolizes carbohydrates. So the liver is involved in storing and metabolizing, that just means breaking down of carbohydrates. That acts as a way of an energy source for my body.

    06:35 It helps me keep a stable blood sugar. So when it comes to metabolism and storage, when we're talking about fats and carbohydrates, bile helps you break down fat to get what you need from it, and it also helps you to metabolize carbohydrates and make a storage place for them. Now, when we talk about the storage of glycogen, the liver takes sugar from the blood in the portal veins and stores it as glycogen. So when I have excess sugar in my bloodstream, let's say I got really hungry, I ate a meal, then my blood sugar rises, part of the liver's job is to take that extra glucose in your bloodstream and store it as glycogen. So, that's when if I need extra energy later, let's say I'm going to go for a run, pugh, yeah, I really don't like running, but if I was to go for a run, then my body would need extra energy, and as I got to running, the liver would start kicking out that stored energy to help me maintain a stable blood sugar because that's the response to a low blood sugar. When you're really hungry, have you ever noticed how irritable people get when they're really hungry? Well, some people are irritable all the time, but I mean what about they're hungry and they're irritable. Well, that's the body's kind of adrenaline. That's a sympathetic nervous system response. It's saying hello, the blood sugar is too low, so the adrenal glands, they squirt out that epinephrine and adrenaline runs around to my liver and tells my liver to kick out that stored energy. That's why people are irritable because they've got that extra adrenaline and epinephrine running around their body, and that's why they're irritable. Give them something to eat, and they'll calm down.

    08:20 Particularly, remember this with little children. So, when we talk about blood sugar, the liver takes any extra sugar that's in my blood and stores it as glycogen in the liver. When I need extra energy, the liver will break that out and let me use that in my bloodstream to help me keep a stable blood sugar. Now, the liver also does some things with proteins. Liver cells change amino acids in foods so they can be used to produce energy. So, we take amino acids.

    08:52 Those are the small building blocks of proteins. The liver cells can change those, that's a process called deamination, and they can help us with energy or make carbohydrates and fats.

    09:04 Now, ammonia is a toxic substance, and that's a byproduct of that process. In the deamination process, ammonia is produced. Now, that's not such a bad thing because the liver has a way of handling it. Liver can convert ammonia to a much less toxic substance called urea. Now, the urea is released into the blood, and that's transported back to the kidneys, and the kidneys should excrete that. Maybe you've heard of a lab test called a BUN, a blood urea nitrogen. This is a blood test that lets us know how the liver is functioning and the kidneys because let's back it up. The liver cells take amino acids in the foods, and they produce energy or make carbohydrates or fats. We've got that down, but part of that process, part of the process of deamination, is ammonia is produced. That's a waste product of this process. Now ammonia shouldn't stay in your body. It needs to be turned into urea. If your ammonia levels get too high, it's neurotoxic, meaning it is toxic to your brain. It can cause severe central nervous system damage, even lead to a coma or death if ammonia levels get too high. So, you got to get rid of that ammonia. That's why the liver has a plan, one of its 500 processes. It takes the ammonia. It turns it into urea that gets sent back through the blood supply to the kidneys, and if they're functioning well, they should get rid of that urea through the urine. So, if a BUN level is high, we need to look at what else is going on in the body. Is it a problem with the liver or is it a problem with the kidneys? But know that breaking down of proteins creates ammonia, ammonia has to be turned into urea so it can be peed out and be water-soluble. If the liver isn't functioning well, an elevated ammonia is a key sign that it's not able to turn that ammonia into urea. Okay, so we've looked at all the things that bile does throughout the body. Right? And we've talked about the impact of the liver on our energy, on fluid volume control, and now let's talk about more of the things it stores. We know it stores energy in the form of glycogen.

    11:23 We know that it breaks down proteins, and in that process, it makes ammonia. We got to get rid of that because it's going to damage your brain. But it also stores the vitamins A, D, E, K, and B12. So, sometimes even up to several years' worth of vitamins can be stored in your liver at one time. I don't know about you, but I think that's pretty impressive. So, the liver also stores minerals. So, we've got energy, we've got glycogen, we've got A, D, E, K, and B12. It stores minerals like iron and copper. Remember how we talked about the iron can be used to remake those red blood cells. Iron comes from that hemoglobin in the form of ferritin, and that is what we actually use to make the new red blood cells. The liver also stores and releases copper. I don't know about you, but the picture in my brain is like these little pennies just shooting out the liver. It's really not like that, but it does store and release copper. So, before we go on, think about liver stores vitamins and minerals; A, D, E, K, B12, iron, and copper. Now, let's take a look at how your liver filters and fights for us. Okay, we're going to look at filtering first. Your liver is a giant filter, and it filters and removes compounds from the body.

    12:47 Now, when we're talking about the kind of compounds it removes, we're talking about hormones. Now, that would be examples of estrogen and aldosterone are 2 examples of hormones that the liver helps us filter out. So, we're talking about filtering things like hormones and compounds from outside of the body. Estrogen and aldosterone are already in our body, but it can also filter the things from outside our body like alcohol or drugs. So, anyone with liver disease is going to have problems with enough of these hormones being removed from the body. So, you're going to see some pretty extreme examples in liver disease that deal with hormones and issues of toxicity. Now, let's talk about how it does the immune system. The liver is a pretty big player in the immune system, particularly the mononuclear phagocyte system. The liver has these cells called Kupffer cells. Now, 80% to 90% of the tissue-based macrophages in your body are these Kupffer cells that live in your liver, and they help bump up your immune system. Because remember a Kupffer cell can swallow up a pathogen or a bad guy or a foreign body that enters your body. So, that's how the liver helps bump up your immune system because these Kupffer cells destroy these disease-causing agents that might enter through the gut. Now, we're going to look at the liver's role in production and pressure.

    14:16 We're talking about production, we're talking about albumin, and if we're speaking of pressure, we're talking about angiotensinogen. Now, let's go back to the production of proteins. Albumin is the most common protein in the blood serum, and it's really important. It's produced in the liver, and you need it in your blood to help you maintain fluid volume balance. Because remember albumin is this large molecule. It also transports fatty acids and steroid hormones, but the way albumin is charged, it attracts sodium which therefore attracts water. So that helps us keep water or fluid in the intravascular space, and it prevents the fluid from leaking into the tissues. So, that's one of the most important reasons that we need your liver to produce enough protein like albumin. Now, let's talk about pressure. How does your liver help you maintain your blood pressure? Well, angiotensinogen is a part of the RAAS system. Right, that's the one you're very familiar with, right, to help in maintaining your blood pressure. So, when your body senses that we need to raise blood pressure for whatever reason, I'm getting ready to run or my blood pressure is too low, then renin from the kidneys connects with this angiotensinogen, and that kicks off the RAAS system. At the end of that, what's the product? Right, angiotensin II and aldosterone. Now, aldosterone tells my body to hang on to sodium, and wherever sodium goes, water follows. So that raises the volume in my intravascular space.

    15:54 That's 1 way the RAAS raises my blood pressure. The other thing is it causes vasoconstriction.

    16:02 So, that's produced by the aldosterone, it says fluid onboard, but angiotensin II causes potent vasoconstriction. So, those blood vessels narrow. So, 2 ways, your blood pressure is raised through the help of your liver. The liver produces angiotensinogen. We need angiotensinogen to connect with renin to kick off that system of RAAS that ends up with aldosterone being secreted, extra volume onboard, and potent vasoconstriction from angiotensin II.

    About the Lecture

    The lecture Unique Characteristics of the Liver: Main Functions (Nursing) by Rhonda Lawes, PhD, RN is from the course Liver Functions and Dysfunctions (Nursing).

    Included Quiz Questions

    1. Support for blood clotting
    2. Metabolism of fats, carbohydrates, and proteins
    3. Synthesis of angiotensinogen
    4. Production of antidiuretic hormone (ADH)
    5. Reabsorption of sodium and potassium for fluid balance
    1. Iron and bilirubin
    2. Iron and bile
    3. Bilirubin and bile
    4. Iron and red blood cells
    1. The liver produces bile, which absorbs vitamin K to create clotting factors.
    2. The liver produces vitamin K, which creates clotting factors.
    3. The liver produces bile, which absorbs nutrients to create clotting factors.
    4. The liver decreases the amount of vitamin K available to prevent bleeding.
    1. When blood sugar levels are low
    2. When blood sugar levels are high
    3. When blood sugar levels are normal
    4. When eating high-fat meals
    1. The liver changes the amino acids in foods so they can be used for energy.
    2. Urea is converted from ammonia and is excreted by the kidneys.
    3. Ammonia is a nontoxic byproduct of protein metabolism.
    4. Low ammonia levels can affect the central nervous system.
    5. Ammonia is excreted by the respiratory system.
    1. Vitamin B12
    2. Copper
    3. Iron
    4. Erythropoietin
    5. Calcium
    1. High estrogen levels
    2. Low aldosterone levels
    3. High glucose levels
    4. Low drug levels
    1. Attracts sodium and water into the intravascular space
    2. Attracts sodium and water into the interstitial space
    3. Rebuilds muscles and tissue
    4. Reduces blood pressure

    Author of lecture Unique Characteristics of the Liver: Main Functions (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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