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.
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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.