The liver is the body’s premier chemical processing factory and largest internal organ. It continuously filters blood, processes nutrients, neutralises toxins, and synthesises essential proteins to maintain metabolic balance.
An adult liver performs over 500 vital functions every single day, working in tandem with almost every organ system in the body.
At any given moment, the liver holds roughly 13% of the body’s total blood supply, filtering approximately 1.4 litres of blood every minute.
The primary functions of the liver are to:
Filter and detoxify blood coming from the digestive tract.
Produce bile to aid in the digestion and absorption of fats.
Store and release glucose, vitamins, and minerals as needed.
Synthesise blood-clotting factors, immune proteins, and cholesterol.
The liver is a large, wedge-shaped organ that is reddish-brown in colour. In an average adult, it weighs between 1.2 and 1.5 kilograms and is roughly the size of a football.
It lies in the upper right quadrant of the abdominal cavity, nestled safely beneath the diaphragm and protected by the lower right ribcage.
Note: While the liver occupies the majority of the upper right abdomen, its left lobe actually extends across the midline of the body into the upper left quadrant.
The top of the liver is smooth and convex, fitting snugly against the curve of the diaphragm. The liver is covered by a protective, fibrous capsule called Glisson’s capsule, which is further enveloped by the peritoneum (the lining of the abdominal cavity).
Four Lobes: The liver is divided externally into two primary lobes—the large right lobe and the smaller left lobe—along with two smaller accessory lobes on its underside, the caudate and quadrate lobes.
Functional Units (Lobules): The liver is made up of roughly 100,000 hexagonal functional units called lobules, each consisting of central veins surrounded by rows of liver cells (hepatocytes).
Dual Blood Supply: Unlike most organs, the liver receives blood from two sources: the hepatic artery (supplying oxygen-rich blood) and the hepatic portal vein (carrying nutrient-rich, deoxygenated blood directly from the intestines).
Biliary Tree: A network of channels collects bile secreted by hepatocytes, draining it into the hepatic ducts, which lead to the gallbladder for storage and eventual release into the small intestine.
The liver functions as a dual processing plant, managing both metabolic breakdown and systemic synthesis through distinct pathways.
The Portal Circulation Loop: The hepatic portal vein delivers blood packed with newly absorbed nutrients, toxins, and drugs straight from the stomach and intestines. The liver inspects, metabolises, or detoxifies these substances before allowing the blood to return to the general circulation via the hepatic vein.
The Metabolic Synthesis Loop: The liver continuously manufactures essential lipids, blood proteins (like albumin), and coagulation factors while breaking down old or damaged red blood cells to recycle iron.
Every metabolic process relies on two core cellular actions:
Anabolism (Storage and Building): When nutrients are abundant, liver cells convert glucose into glycogen for storage and bundle fats into lipoproteins.
Catabolism (Breakdown and Clearance): When the body requires energy or clearance, the liver converts glycogen back into glucose and breaks down harmful ammonia into urea.
The liver’s structural architecture is perfectly optimised to manage this workflow:
Hepatocytes: These primary liver cells execute the bulk of metabolic, secretory, and detoxifying functions.
Kupffer Cells: Fixed macrophages within the liver’s blood channels (sinusoids) that engulf and destroy bacteria, foreign debris, and aged blood cells.
Stellate Cells: Cells located in the perisinusoidal space that primarily store Vitamin A, but can transform into collagen-producing cells during liver injury.
Fascinating Liver Fact: The liver possesses an extraordinary capacity to regenerate. Even if up to 70% of its tissue is surgically removed or damaged, it can completely grow back to its original size within a few weeks.
The liver does much more than clear waste from the body.
Glucose Regulation: By storing glucose as glycogen and releasing it when blood sugar drops, the liver actively maintains stable systemic energy levels.
Responding to Fasting: During periods of starvation or heavy exercise, the liver initiates gluconeogenesis—creating glucose from non-carbohydrate sources like amino acids to fuel the brain.
Supporting Immune Defence: By housing a massive colony of immune cells, the liver acts as a critical filter that captures and destroys gut-derived pathogens before they enter systemic circulation.
Hormone Processing: The liver metabolises and clears hormones from the bloodstream, including insulin, glucagon, estrogen, and cortisol, preventing hormonal imbalances.
Working with Other Organs: The liver works closely with the gallbladder and pancreas to manage digestion, and collaborates with the kidneys to filter urea and regulate systemic fluid dynamics.
Non-Alcoholic Fatty Liver Disease (NAFLD): NAFLD (now frequently referred to as MASLD) occurs when excess fat accumulates in liver cells, often tied to metabolic factors like obesity and type 2 diabetes. It is one of the fastest-growing causes of liver disease worldwide.
Cirrhosis: Cirrhosis is the advanced stage of liver fibrosis, occurring when healthy liver tissue is permanently replaced by scar tissue due to long-term injury. This prevents the liver from functioning properly.
Hepatitis: An inflammation of the liver, most commonly caused by viral infections (Hepatitis A, B, C, D, and E), but also triggered by heavy alcohol consumption, toxins, or autoimmune responses.
Alcohol-Related Liver Disease (ARLD): Damage caused by excessive alcohol consumption over many years, progressing from simple fatty liver to alcoholic hepatitis and, ultimately, irreversible cirrhosis.
Liver Cancer: Primarily manifesting as hepatocellular carcinoma (HCC), liver cancer often develops in individuals with pre-existing chronic liver disease, cirrhosis, or chronic hepatitis B or C infections.
Doctors commonly assess liver health using:
Liver Function Tests (LFTs): A panel of blood tests that measure specific enzymes and proteins, including Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), and Alkaline Phosphatase (ALP). Elevated levels typically indicate liver cell damage or bile duct obstruction.
Bilirubin levels: Measures the amount of bilirubin (a byproduct of red blood cell breakdown) in the blood; high levels cause jaundice (yellowing of the skin and eyes) and suggest liver or gallbladder dysfunction.
Albumin and Prothrombin Time (PT): These tests assess the liver’s synthetic function—measuring its ability to produce essential proteins (albumin) and blood-clotting factors (PT/INR).
Abdominal Ultrasound: A non-invasive imaging scan that uses sound waves to visualise the liver’s size, shape, blood flow, and the presence of fat accumulation or tumours.
Transient Elastography (FibroScan): A specialised ultrasound-based technology that measures liver stiffness, helping doctors quantify the degree of liver scarring (fibrosis) without requiring an invasive biopsy.
Maintaining a healthy metabolic engine relies heavily on daily lifestyle choices that protect liver cells from inflammation and scarring.
Dietary Choices: Eating a balanced diet high in cruciferous vegetables, whole grains, coffee, and healthy fats (like olive oil) reduces fat accumulation and oxidative stress within liver tissue.
Regular Exercise: Engaging in regular aerobic and resistance exercise burns triglycerides, which helps directly lower fat accumulation in liver cells independent of weight loss.
Moderating Alcohol Consumption: Limiting or avoiding alcohol prevents the toxic accumulation of acetaldehyde, a destructive byproduct of alcohol metabolism that destroys liver cells.
Medication Safety: Avoiding the misuse of over-the-counter medications—especially paracetamol (acetaminophen)—and avoiding mixing medications with alcohol prevents acute, drug-induced liver failure.
Routine Screening: Especially for individuals with metabolic syndrome, type 2 diabetes, or a history of heavy alcohol use, regular tracking of liver enzymes allows for early identification of liver stress before irreversible damage occurs.
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