What kind of functions do liver perform?

Hello friends.

This time I am here with a very exciting and probably one of the very important and useful topic for you. That is, describing about hepatitis viruses and its types.

We all have heard about hepatitis, or many of us know that there is more than 1 type of it such as hepatitis A or B. Actually, there are more than these. But more importantly, I want us to skip one step back and question: Do you know that hepatitis is viral and non-viral? And the types that we usually hear about are related with viral hepatitis?

Well, viral hepatitis is more common than any other hepatitis.

So, in this article we will learn about:

  • Hepatitis
  • Non-viral hepatitis
  • Functions of liver
    • What is bile and its function?
    • What is cholesterol?
    • How liver helps in blood formation?
    • Role of liver in waste removal
    • What is bilirubin and biliverdin?
    • And much more…

Hepatitis

Hepatitis is the inflammation of liver. As liver (why?) is a very vital organ, taking part into various bodily activities, its damage can lead to many serious complications. This inflammation can be caused by many viruses and non-viral causes.

Non-Viral hepatitis: Hepatitis that is caused by anything but virus. This can be:

  • Autoimmune (Ai) hepatitis- When our immune cells target our liver.
    • There are type 1 and type 2 Ai hepatitis. Type 1 is more common, occurs at any age and is associated with other Ai disease like ulcerative colitis or rheumatoid arthritis. Whereas, type 2 is seen often in young age.
    • Symptoms- Inflamed and enlarged liver, jaundice, pain or uneasiness in upper abdomen.
    • Treatment- Medications are used to prevent further progress or slow down the damage of liver. One such medicine is Prednisone or Deltasone, a glucocorticoid for anti-inflammatory effect. It can be used along with Azathioprine or Imuran, another immunosuppressive medicine which is slow but can be effective. However, using medication for long has its own adverse effects and is not always effective. The permanent cure is liver transplantation especially when liver damage is irreversible.
  • Other causes of hepatitis can be drugs or toxins.

Now, what is hepatitis?

You may say that that is what we have just talked about now. But when you see it, it’s not complete information about hepatitis. To make it a little bit more of a complete discussion, we have to talk about symptoms also.

Symptoms:

  • Episodic fever
  • Jaundice
    • A condition of yellowing of skin, sclera or white of eye (the earliest most recognisable sign of jaundice).
    • Caused due to accumulation of bilirubin in serum.
  • Abdominal pain
  • Nausea or vomiting
  • Dark colored urine
    • Urine gets dark colored due to excretion of bilirubin through kidney.
  • Joint pain

Now, before we start our session on hepatitis, we must understand exactly why liver damage is scary. Also, you will get a clearer picture of what is bilirubin exactly. In the following journey, I will explain in detailed manner why liver is very vital for us. So, let’s head on.

What are the functions of liver?

Liver is the not the largest gland of our body for no reason. Just like you I also used to think, why it is the largest gland, how many functions and what types of functions it perform. But you do not have to wait for years to know about it. Here, I have explained about it perfectly. I will calm your curiosity here on out.

Liver is a very vital organ for us because it performs:

  • The production of bile.
    • A fluid with digestion and wastage carrying function that is stored in gall bladder after being produced by liver. How it helps in digestion is still a mystery! No, just kidding, it’s not a mystery.
    • Actually, it contains bile salts which are produced from cholesterol. Bile salts are bile acids which are conjugated with amino acids like taurine and glycine (the simplest amino acid).
    • This bile salt degrades the complex fat substances into simpler, smaller compounds. On which the enzymes can easily work on and which are easy to absorb.
  • The production of cholesterol and lipoproteins (fats).
    • Cholesterol is an important precursor for synthesis of many steroidal hormones such as corticoids (glucocorticoids and mineralocorticoids produced by cortex of adrenal glands), sex hormones (androgen and estrogen produced by gonads). Also cholesterol molecules are integrated in our cell membrane providing them rigidity and strength to withhold the cellular structure and shape.
    • Lipoproteins (that is substances that has fat and protein together) carries cholesterol throughout the blood. You are all aware of them. Once in a lifetime, you have heard or spoken about it too. They are popularly known as by good and bad cholesterol for high density lipoprotein (HDL) and LDL respectively.
  • The production of certain proteins like albumin, fibrinogen etc.
    • Albumin is important for osmotic balance. Therefore, its imbalance can lead to fluid retention in legs leading to their swelling.
    • Fibrinogen is important for blood coagulation.
  • One of the most important function in our body. And that is glycogensis i.e. conversion of glucose into glycogen for storage in liver and skeletal muscles.
    • And the reverse metabolic pathway or glycogenolysis is again performed by liver. Not only that, to maintain glucose homeostasis in body by different mechanisms such as glycolysis and gluconeogenesis are also done by liver cells.
  • Urea production.
    • The mitochondria of liver cells perform ornithine (urea) cycle to produce urea from the ammonia.
    • Ammonia is a waste product produced in our body by our cells during their metabolism or by bacteria present in our gut. It is highly toxic to our cells and can lead to their destruction therefore its removal is quite a concern for our body. This, hence, is either achieved by incorporating it into amino acid such as glutamine by the process called ammonia detoxification. Or can be converted into urea by urea cycle. Both of these processes occur in liver.
    • Urea is again a nitrogenous waste product, however it is less toxic to our body. Then through blood it is excreted via kidney into urine.
  • Amino acid (AA) metabolism. I have given you a glimpse of how it is also important for glutamate (Glu) production. Just like that
    • Liver produces many other AA’s such as glycine (Gly), serine (Ser), alanine (Ala), aspartate (Asp) etc. (Q#1)
    • Also, not only their production, they are broken down to produce other biological components like carbohydrates (glucose) via gluconeogenesis, fats (if the protein is in abundance).
  • The production or at least the regulatory function of production of erythrocytes (RBC’s).
    • You may find it interesting but earlier before the bone marrow formation, it was the liver that used to perform RBC’s formation in embryonic stage. (Q#2)
    • During adult stage, liver produces erythropoietin (EPO) hormone when the circulating RBC’s gets significantly reduced. Normally, liver has miniscule role in EPO formation in post-natal period. And this role is carried out by kidney as now they are the major contributor of EPO formation.
  • The production of many important clotting factors therefore regulating blood coagulation in a sense too.
    • Yes, not only blood cells but even blood coagulation factors are produced within liver cells.
    • As I have mentioned one of them earlier (can you guess where), it forms factors such as factor I,  II (prothrombin), V (proaccelerin), VII (proconvertin), IX (christmas factor), X (Stuar-prower factor), XI (plasma thromboplastin antecedent), XII (Hagmen factor).
  • The destruction of RBC’s.
    • Along with spleen, liver is also the destroyer of senescent RBC’s.
  • The production of bilirubin.
    • It is a brown-yellow pigment that is formed from the destruction of RBC’s (heme) either in liver and premature cells in bone marrow.
    • It contains heme (a protein found in Hb) which is excreted through bile and also perform as antioxidant and protects against lipid peroxidation. It does this by getting oxidised into biliverdin (a green pigment formed by bilirubin reductase enzyme).
  • Metabolising and neutralising vast number of drugs, toxins.
    • When drugs are administered into inactive form i.e. prodrugs, they must pass through liver for activation.
    • This metabolism occurs due to the action of cytochrome P450 enzymes which are primarily found in liver. These are monooxygenases that catalyse the oxidation and are involved in cellular metabolism.

Q#1. Do you know which AA’s are essential and which one’s are not?

A#1. Are you familiar with the concept of essential and non-essential AA’s?

Huh! What’s with me? Instead of answering the question, I put up another one.

Well, essential and non-essential AA’s mean those that can’t be produced within the body and those that can be. If there are AA’s that can’t be produced within our system, they must be provided from outside source. Such AA’s are called, essential ones.

For eg, histidine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), methionine (Met), phenylalanine (Phe), threonine (Thr), tryptophan (Trp), and valine (Val).

And what are the examples of non-essential AA’s? well, you know few of them.

I also want to point out that, there are 20 AA’s that we talk about the most. But why is that? Because they are the ones that are used in our body to synthesize proteins. But in reality there are around 500 or more.

Q#2. What do you think, which organ is used to form blood cells before liver?

A#2. You can say that, just like bone marrow, liver is also not the 1st RBC’s forming organ as it is also not developed from the starting of fetal development.

Therefore, in the embryonic period, the 1st structure that forms the blood cells is yolk sac.

It is a membranous sac that has a nutritive role to the developing embryo. It develops at around 4 week of gestation and disappears before the end of 1st trimester.

Whereas the liver forms at the middle of 2nd trimester.

However, the bone marrow also starts developing at a similar time i.e. in the 2nd trimester. Liver is still the primary site for EPO production in embryo.

So, I think you have gotten a glimpse of why liver is such a crucial organ to our body. Honestly, each organ and structure in our body has leading list of functions. But why liver stands out among them, this idea you may have gotten now.

Therefore, it covers the 1st part of the article. In the next part, I will focus on hepatitis. We will meet again in the next week. Well you can come at any time and ask me anything by commenting in the comment box.

But before heading out, don’t forget to check your knowledge. Try to answer these questions:

  • What is autoimmune hepatitis? Is it a viral or non-viral hepatitis?
  • Name a few symptoms of hepatitis
  • What are bile, bilirubin, biliverdin?
  • Some functions of cholesterol
  • How liver is crucial for
    • Osmotic homeostasis
    • Blood coagulation
    • Blood formation
  • Which system helps in hepatocytes against drugs and pathogens?
  • What are essential and non-essential amino acids?
  • What structure are involved in red blood cells formation during our natal and post natal period of life?

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