The liver is the largest internal organ and sits in the right upper quadrant under the ribs. It receives blood from both the hepatic artery and the portal vein.
Blood supply
About three quarters of liver blood arrives through the portal vein, carrying nutrients and drugs from the gut. The hepatic artery brings oxygen-rich blood, and the hepatic veins drain into the inferior vena cava.
Lobules
Liver cells (hepatocytes) form small lobules around a central vein. Blood flows past them through sinusoids, where the cells take up, process and release substances.
Making proteins
The liver makes albumin, which holds fluid inside the blood vessels, and most clotting factors. Low albumin causes swelling, and a high INR shows poor production of clotting factors.
Metabolism and clearance
It stores glucose as glycogen, makes cholesterol and turns ammonia into urea. It also breaks down many drugs and conjugates bilirubin so it can leave in bile.
| Function | Lab test | When it fails |
|---|---|---|
| Making clotting factors | INR | Easy bleeding and bruising |
| Making albumin | Albumin | Edema and ascites |
| Clearing bilirubin | Bilirubin | Jaundice |
| Liver cell integrity | ALT and AST | Rise when liver cells are injured |
At the bedside
Jaundice, ascites, easy bruising and confusion are signs of a failing liver. Liver function tests and the INR show how much function is left.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).