I mean frankly, the liver performs so many necessary functions that it’s almost boring. The liver is like that movie in the Oscars that wins every award…best screen play, best performance, best soundtrack…and you’re like “come on, give someone else a little credit.” Well when it comes to the body the liver deserves all the credit. For starters the people who write textbooks can’t even decide what organ system to put the liver in. It produces enzymes that are necessary for the emulsion of fat, and the metabolism of proteins and carbohydrates so obviously it’s part of the digestive system…well kinda. It has a hefty blood supply, produces lymph, and harbors antibodies for the destruction and removal of old and ineffective red cells so maybe it’s part of the immune system…well kinda. It produces an [EXPLETIVE] load of useful proteins that aid in everything from helping your blood to clot to detoxifying drugs, and toxins that enter the blood stream so….don’t look at me, your guess is as good as mine. If you want a meeting with the Liver you’ve got to ride the elevator to the top floor, follow the arrows to the door labelled “The Man” and wait in line. Well ok, this stays between me and you, but I can tell you what I know. Keep your voice down and close the door behind you…
The Liver is the original Renaissance man. I mean forget the Dos Equis commercials. Just take a look at this organ’s resume..
glycogen synthesis and degradation, gluconeogenesis from protein, amino acid, and lipid / non-carbohydrate sources
drug metabolism and detoxification
synthesis of bile salts…nasty but necessary
plasma proteins, cholesterol and its carrier lipoproteins
And I wouldn’t be suprised if it knows magic tricks
Digestion and Metabolism
The liver produces bile which looks a lot like it sounds, nasty, but it gets stored in the gallbladder to aid in the breakdown of lipids (fats basically) in the small intestine.
About that whole bile thing…
bile facilitates the action of pancreatic amylase which actually degrades triglycerides. The bile’s salts have two sides, molecularly speaking, hydrophobic and hydrophyllic. The main reason why fats don’t dissolve in water is because their molecular surface repells water. So bile salts can surround fats with their water loving (hydrophillic) sides out which gives enzymes like pancreatic amylase the back stage pass.
So not only does the Liver make cholesterol but it produces the carrier molecules, lipoproteins like HDL and LDL that transport the stuff. Cholesterols are insoluble in water so the lipoproteins facilitate their deep sea journey through the bloodstream.
Some light anatomy
so the main cellular component of the liver is the hepatocyte. They make up roughly 70-80% of the total mass so naturally, because I do choose favorites, that’s what I’m focusing on in this article. They are the working parts of the organ that together make the magic happen. An organ is the sum of it’s parts…microscopic processes equating to bigtime changes. Ah yes, and it get’s it’s hefty blood supply from the hepatic arteries and portal vein. Now you know in case Jay Leno asks you in the street. You’re welcome.
When I say metabolism I want you to think “what happens to the glucose?” Let’s say it’s half priced Tuesday at The Gringo Burger Bodega (I made that name up. Can you tell?) and you’ve treated yourself to the #6 diablo fries with a dulce shake made extra dulce. While being transported to takeout heaven you wonder “What is my body doing with that access glucose?” You’re always thinking. I love that!
Here’s what happens…
Blood from your portal vein supplies your hepatocytes with fresh glucose. Those cells will form long chains of the glucose molecules linked by a-1,4 glycosidic bonds to form this nice biggie sized storage form of energy called glycogen which happens when your blood glucose levels are high hence there is a raise in blood sugar so having all those hepatocytes uptake glucose lowers blood sugar. So in classic, clever physiology fashion when blood sugar is low the glycogen can be broken down/degraded into glucose which is then available to adjust for blood glucose level.
Another neat trick…
The other thing you have to know about the liver is that it doesn’t like to let anything go to waste. If it’s an organic molecule and your body can make use of it, chances are your liver is breaking it down and recycling it as we speak…no seriously, like just now. oh you missed it.
Sometimes carbohydrates just aren’t enough. Sorry blue box mac n cheese, I know we go way back but it’s true. The body needs a way to derive glucose, that oh so sexy cellular currency, from non-carbohydrate sources. The process by which the liver pulls this off is of course referred to by the cool kids (scientists) as gluconeogenesis. Your kidneys can also pull this off, but don’t get too excited about this clever trick. It’s just another way the body compensates for potentially “bad news” drops in blood glucose apart from the breakdown of glycogen. It’s the kinda thing that is supposed to kick in when you’ve been fasting, starving, or exercising like you’ve been possessed by demons.
Detox Rocks! (see what I did there)
So one more thing…
The liver is probably the best defense our body has to protect us from ourselves. If it’s toxic or in a form the body can’t use…the liver will convert, breakdown, and package it like there’s no tomorrow..because if it didn’t there really would be no tomorrow. This is typically referred to as xenobiotic metabolism and it’s made possible by the bountiful community of enzymes and their biochemical pathways that call the liver home. The liver typically accomplishes this by modifying the fat loving (lipophilic) nature of many pharmaceuticals into a more user friendly and excretion friendly, water loving (hydrophilic) form. However, it’s not always about solubility. Some nasty little substances require a little versatility (I’m looking at you Alcohol..you know what you did last weekend). Thankfully our livers come equipped with a nifty alcohol dehydrogenase that allows for the reduction reactions that keep this party animal in its cage reasonably well.
I should mention however that the liver’s gift can also be its curse. The liver has such mad skillz for the bio-conversion of compounds that every now and then it can convert foreign compounds into substances that are actually more toxic than what you started with. We call these metabolites and they are no fun.
Well my friends it’s time for me to go make a difference (eat dinner). Stay curious, stay classy, and as always never stop learning 🙂