Liver: The Organ of Life

The liver is one of the most vital organs in the human body and plays an important role in various physiological processes. The liver in the human body is located on the right side of the upper abdominal portion near the stomach and intestines and beneath the diaphragm. It weighs approximately 1.5kg in adults. The cells of the liver are called hepatocytes, and the study of the liver is known as hepatology.

1.0Liver Anatomy

• The Liver Anatomy starts with its division into two lobes, namely the right lop (larger) and the left lobe (smaller). 
• The Liver consists of functional units called lobules, which are the basic structural or the building blocks of the liver. 
• Each lobule consists of hepatocytes (liver cells) that are in plates radiating from a central vein.
• Sinusoids are capillaries within the liver lobules where blood flows and undergo filtration and exchange.
• The hepatic portal vein brings deoxygenated blood from the intestines, which contain nutrients and toxins, to be processed by the liver.
• The hepatic artery supplies pure/oxygenated blood to the liver.
• Bile ducts carry bile produced by hepatocytes to the gallbladder and small intestine.

2.0Functions of the Liver

1. Metabolism of Nutrients : The liver helps in many metabolic activities that help in providing energy to the body. Some of them are: 

• It converts and stores glucose into glycogen (glycogenesis).
• It may also convert glycogen back into glucose when the body needs energy. 
• It helps in the metabolism of different macronutrients - fats, proteins, and carbohydrates - by secreting its juices (bile juice) into the digestive tract. 

2. Detoxification: The liver also works as a detoxifying organ. Detoxification is the breaking down and neutralisation of harmful substances like drugs, alcohol, and metabolic waste products, such as converting ammonia into urea, which is then excreted by the kidneys. 
3. Bile Production and Secretion: Bile juice is essential for digestion and absorption of fats in the digestive tract. It provides a basic pH for the acidic food coming from the stomach, which protects our intestines from the harmful effects of gastric acid. Bile juice is stored in the gallbladder and released into the small intestine when needed. 
4. Regulation of Blood Clotting: It manufactures blood clotting factors such as Prothrombin and fibrinogen, which are the main components for the clotting of blood, hence preventing excessive blood loss. 
5. Blood Circulation in the Liver: the Hepatic Portal System 

• As mentioned earlier, the liver processes the nutrients and also detoxifies harmful substances. But the question is: How do these substances reach the liver? The answer is the Hepatic Portal system. The system is the specialised network of veins that plays an important role in transporting blood from the digestive organs to the liver. 
• The System carries blood from the intestines, spleen, and pancreas to the liver for processing, and after being processed, blood is transferred to the heart via the inferior Vena Cava. 

3.0Liver Diseases

Liver conditions can vary from mild to injurious in terms of severity. These liver ailments can impair the liver’s function temporarily as well as permanently. Some of them are: 

• Hepatitis: Inflammation of the liver is mostly caused by various viral infections like Hepatitis A, B, C, etc., alcohol, or toxins. Symptoms of hepatitis are fatigue, jaundice (yellowing of skin and eyes), and abdominal pain.
• Cirrhosis: Scarring of the liver tissue, mainly due to chronic alcohol abuse or viral hepatitis. It impairs liver function and can lead to liver failure.
• Fatty Liver Disease (NAFLD): Accumulation of fat in the liver cells. Fatty liver symptoms often include obesity, diabetes, and excessive alcohol use. Fat liver disease causes tiredness, discomfort in the abdomen, and an enlarged liver.
• Liver Cancer: Known as hepatocellular carcinoma, cancer develops most frequently in individuals who suffer from chronic diseases such as cirrhosis and hepatitis.
• Jaundice: Yellowing of the skin & sclera (white part of the eyes) is caused due to excess bilirubin in the blood. It is a symptom of liver disease or bile duct obstruction.
• Liver Failure: when the liver loses its ability to function due to extensive damage. It can be acute (sudden) or chronic (long-term).

4.0Liver Function Test (LFTs)

The liver function test (LFT), also known as the Hepatic panel or liver panel, is a series of tests of different enzymes and proteins that contribute to liver health. Any increase or decrease in these enzymes and proteins may lead to Liver dysfunction. Some Examples of LFT are: 

1. Alanine Aminotransferase (ALT): ALT is an enzyme mainly in the liver. High ALT levels in the blood indicate liver cell damage or inflammation that is commonly caused by diseases such as hepatitis or fatty liver. It is a sensitive marker of liver injury.
2. Aspartate Aminotransferase (AST): AST is a type of enzyme that can be found in the liver, heart, and muscles. It is usually tested simultaneously with ALT. High levels of AST can suggest liver damage, but it could also point to heart or muscle conditions. The ratio of ALT to AST is often used to diagnose liver damage specifically.
3. Alkaline Phosphatase (ALP): ALP is an enzyme present in the liver, bones, and bile ducts. Elevated levels are suggestive of liver or bile duct disease, such as cholestasis (obstruction of bile flow) or gallstones. It is often used to assess the health of the biliary system.
4. Bilirubin (Total and Direct): Bilirubin is a product of hemolysis or the breaking down of red blood cells. An elevated level of bilirubin in the blood can cause jaundice (yellowing of the skin and eyes) that is associated with liver diseases, such as cirrhosis or bile duct obstruction. Bilirubin is reported as total and direct (conjugated) bilirubin.
5. Albumin: Albumin is a protein produced by the liver, which helps in maintaining blood pressure and fluid balance. Low levels of albumin indicate liver disease, such as cirrhosis, where the ability of the liver to produce proteins is impaired.

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