Liver: Biology PSC Notes

The liver is the largest internal organ inside the human body. It is a wedge-shaped organ that is reddish-brown in color. In human adults, the liver weighs approximately around 1.4 Kg (1400g), it varies according to the gender. It is a part of the gastrointestinal system.

Facts about Liver

  • Largest gland in the body.
  • Found only in Vertebrates.
  • Human Liver consists of 96% water.
  • Largest waste disposal organ in the body.
  • Filters about 1.7 liters of blood per minute.
  • Produces approximately 1 Litre of bile per day.
  • Most enzymes are secreted by the Liver.
  • Only organ with the ability to regenerate naturally.
  • The organ that liberates the largest amount of heat.
  • Second largest organ in the body (first being the skin).
  • Only organ that synthesizes and store Vitamin A (excess of, about 2 years) & Fat.
If 25% of liver cells are left, while 75 % are damaged, the liver can regenerate within 8-25 days.

Structure of Liver

Structure of Liver

The liver lies on the right-hand side of the abdominal cavity underneath the diaphragm and behind the ribs. There are two large blood vessels that carry blood to the liver. They are
  • Hepatic Artery – brings blood from the heart via the aorta.
  • Portal Vein – brings digested food from the small intestine as well as carries blood into the liver.
Inside the liver, these blood vessels are further divided into small branches called capillaries. Each of these capillaries leads to a nodule and these nodules are in turn made up of hepatic cells.

The branch of medicine concerned with the study of the liver is called Hepatology (ഹെപ്പറ്റോളജി).

Functions of Liver

The liver is capable of performing more than 500 functions inside the human body. Some of the functions of the Liver are as follows:
  • Cleans the blood by detoxifying poisonous substances that enter the body.
  • Stores Vitamins (A, D, K & B12), minerals, fats, sugars and iron (in huge amounts).
  • Helps in the clotting of the blood.
  • Produces enzymes.
  • Produces hormones such as Insulin-like Growth Factor-1 (IGF-1), Hepcidin, Betatrophin, etc
  • Secretes proteins like Albumin, Prothrombin, Serum amyloid A (SAA) & Fibrinogen.
  • Performs immunological functions by using Kupffer cells to remove harmful substances in the bloodstream.
  • Performs metabolic functions such as:
    • Breaks down hemoglobin & produces Bilirubin.
    • Breaks down proteins into amino acids.
    • Breaking down of excess amino acids into Ammonia and which in turn combines with CO2 to form urea.
    • Produces a digestive juice called bile, yellow-green liquid which breaks down fats in the bloodstream so they can be absorbed by the body.
    • Breaks down the carbohydrates into glucose and it gets stored in the liver as glycogen.
  • The digestive juice without enzyme – Bile
As the liver is a major regulator of ammonia and plasma glucose levels, any imbalance in these levels may result in Hepatic encephalopathy, a condition where the brain function declines.

Because of these functions, liver is considered as the biochemical laboratory of the human body.

Liver Diseases

  • Alcoholic Liver Disease
  • Cancer
  • Cirrhosis
  • Fascioliasis - caused by parasite liver fluke.
  • Fatty Liver
  • Jaundice
  • Hepatitis (A, B & C)
  • Reye syndrome – affects both liver and brain.
  • Hemochromatosis (Iron overload, Hereditary disease).
  • Wilson disease (excess copper builds up, hereditary disease, affects the brain as well).

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📝 SideNotes:

  • First successful whole human liver transplant occurred in – 1967.
    • – by American physician Thomas Starzl.
  • First successful deceased donor liver transplant (DDLT) in India – 1998.
    • First successful Living donor liver transplant (LDLT) in India – November 1998.
      • – by Rajashekar
  • The bile is stored in – Gall bladder.
  • Largest endocrine gland in human body – Thyroid.
  • Excessive consumption of alcoholic drinks causes damage to – Liver. (Previous PSC Questions: Women Civil Excise Officer, 2018)
  • Dipsomania – Uncontrollable intermittent bouts of craving for alcohol.
  • Which is not an Endocrine gland? (Previous PSC Questions: Junior Health Inspector, 2015)
    • (A) Thyroid (B) Adrenal gland (C) Pituitary gland (D) Liver
  • Fat soluble Vitamins are mainly stored in – Liver. (Previous PSC Questions: Higher Secondary School Teacher- Homescience, Higher Secondary Education, 2016)
  • The lipoprotein which removes cholesterol from peripheral tissues and transport it to liver is – HDL. (Previous PSC Questions: Senior Lecture/ Lecture In Neuro Surgery/ Gynecology, 2016)
  • The lipoprotein which helps the transport of TAG synthesized by the liver is – VLDL. (Previous PSC Questions: Junior Scientific Officer, Chemical Examinations Laboratory, 2017)
  • Vitamin A is mostly stored in which type of cells in the liver – Stellate/ito cells. (Previous PSC Questions: Senior Lecture/ Lecture In Neuro Surgery/ Gynecology, 2016)
  • Activation of Gluconeogenesis in liver is achieved by inhibiting one of the key enzymes in the Glycolysis. Which of the following Enzyme is inhibited? (Previous PSC Questions: Junior Scientific Officer, Chemical Examinations Laboratory, 2017)
    • (A) Hexokinase (B) Phospho Fructo Kinase-1 (C) Pyruvate Kinase (D) Phospho Fructo Kinase-2