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Liver

life science Maturity 9-11 Vital Level 3 Next article →

The liver is a vital metabolic organ found in all vertebrates. It is often described as the body's chemical factory. This nickname exists because the organ performs a massive variety of tasks. Scientists estimate that the liver carries out around 500 different functions. These roles include the detoxification of the organism and the synthesis of proteins. It also produces biochemicals necessary for growth and digestion.

Human Hepar
Human Hepar

To perform these complex jobs, the liver relies on specialized tissue. Most of this tissue is made of cells called hepatocytes. These cells are the basic metabolic units of the organ. They work within functional units called hepatic lobules. Each lobule is roughly hexagonal in shape. Within these lobules, blood flows through small capillaries known as sinusoids.

Hepatic structure2
Hepatic structure2

The liver receives blood through two distinct major vessels. The hepatic artery carries oxygen-rich blood from the aorta. This blood travels via the celiac trunk to reach the organ. The portal vein carries a different kind of blood. It brings blood rich in digested nutrients from the gastrointestinal tract. This blood also comes from the spleen and the pancreas. Once inside, these vessels subdivide into the tiny sinusoids. These sinusoids lead directly to the hepatic lobules for processing.

Anatomically, the liver has a very specific structure. It is a dark reddish-brown, wedge-shaped organ. It is both the largest gland and the heaviest internal organ in the human body. In humans, the liver is divided into two lobes when viewed from above. These are the right and left lobes, separated by the falciform ligament.

Gray1085
Gray1085

When viewed from below, the liver shows four parts. These include the left, right, caudate, and quadrate lobes. Doctors can also use Cantlie's line to divide the liver into two halves. This imaginary line runs from the vena cava to the gallbladder.

Sobo 1906 389
Sobo 1906 389

The liver's location is protected within the abdominal cavity. It sits in the right upper quadrant, just below the diaphragm. The lower right rib cage helps shield it from injury.

Gray1087-liver
Gray1087-liver

The organ's surface is covered by a serous coat called the peritoneum. It also has a fibrous capsule known as Glisson's capsule. This capsule is named after the British doctor Francis Glisson. The liver also creates specific impressions on its surface. These impressions accommodate nearby structures like the stomach, kidney, and duodenum.

Gray1087-liver
Gray1087-liver

One of the most important processes is the production of bile. The liver produces this alkaline fluid, which contains bile acids and cholesterol. Bile helps to emulsify and break up dietary fat during digestion. The gallbladder, a small hollow pouch, sits just under the right lobe. It stores and concentrates the bile produced by the liver. The bile is later excreted to the duodenum to assist with digestion.

Hilum of the liver
Hilum of the liver

Medical professionals use the Couinaud classification system to map the organ. This system divides the functional lobes into eight independent segments. Each segment has its own specific vascular inflow and outflow. It also has its own biliary drainage. The segments are numbered I through VIII in a clockwise fashion. Segment I is the caudate lobe, which is unique because it receives blood from both the left and right vascular branches.

Liver 04 Couinaud classification animation
Liver 04 Couinaud classification animation

Because the liver is so essential, its health is critical for survival. If the liver fails completely, the only option is a liver transplantation. While doctors can use liver dialysis for short-term help, they cannot yet replace the organ long-term. This is because no artificial liver has been developed for permanent use. The liver remains a complex and irreplaceable part of the vertebrate body.

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🖼️ Images & Media (16)
File:Gray1085.png
Gray1085.png
File:Sobo 1906 389.png
Sobo 1906 389.png
File:Human Hepar.jpg
Human Hepar.jpg
File:Gray1087-liver.png
Gray1087-liver.png
File:Hepatic structure2.svg
Hepatic structure2.svg
File:Hilum of the liver.png
Hilum of the liver.png
File:Liver 04 Couinaud classification animation.gif
Liver 04 Couinaud classification animation.gif
File:CT Scan Thorax Liver.jpg
CT Scan Thorax Liver.jpg
File:Ultrasound liver right lobe and right kidney.jpg
Ultrasound liver right lobe and right kidney.jpg
File:Diagram showing the position of the perihilar bile ducts CRUK 357.svg
Diagram showing the position of the...
File:Big Liver Tumor.JPG
Big Liver Tumor.JPG
File:Scleral Icterus.jpg
Scleral Icterus.jpg

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