The liver is triangular or coned-shaped, having a reddish-brown coloration, and at about 1.5kg and 15cm in width, estimated at 2% of the total body weight.

The liver is located in the upper right quadrant region of the abdomen. It is just beneath the diaphragm and at the top of the stomach and small intestines.

The entire liver surface is covered with a serous membrane of the peritoneum.

The liver is divided into the left and right lobes, having unequal morphology as well, and when we examine it from below, it is divided into the left lobe, right lobe, caudate lobe, and quadrate lobe.

The chief functional unit of the liver is the hepatic lobules. The hexagonal lobule has a triad (portal vein, bile duct, and hepatic artery).

Each lobule possesses 1 million hepatocytes, the actual site of metabolic activities.

A layer of thin, opaque, and irregular fibroelastic connective tissues is responsible for adhering to all the lobules and forming a capsule known as Glisson’s Capsule. The tissues of Glisson’s Capsule go along with the liver lobules’ nerves, ducts, and arteries.

Histologically, the liver has two types of cells: parenchymal and non-parenchymal.
The liver sinusoid is just like a fenestrated capillary having discontinuous endothelium to receive oxygen and nutrient-rich blood.

The liver sinusoid also possesses phagocytic Kupffer cells that destroy harmful external bodies.

BLOOD SUPPLY:

The liver receives a dual blood supply, i.e.

It receives oxygen-rich blood from the Hepatic artery, accounting for about 25% of the total blood supply to the liver.

The hepatic portal vein delivers 75% blood to the liver. This blood supply is nutrient-rich and venous return from the G.I.T. and nearby organs to the liver.

PHYSIOLOGY OF THE LIVER:

The liver plays an active role in digestion through the synthesis of bile.
Bile is a mixture of water, bile salts, cholesterol, electrolytes, bile pigments, and bilirubin.
Hepatocytes of the liver are responsible for bile production, which then travels through bile canaliculi and reaches the duodenum or is stored in the gall bladder.
When the food with fats reaches the duodenum, the duodenum cells release cholecystokinin to stimulate the gall bladder to release bile.
Bile travels through the bile duct and reaches the duodenum, emulsifying the large fat molecules. This emulsification turns large clumps of fat into smaller ones and becomes easy to absorb.

• Excretion of bilirubin:

Reticuloendothelial cells are the phagocytic cells of the liver responsible for breaking old or abnormal R.B.C.s.
They take up the R.B.C.s and break their hemoglobin into its components, haem and globin. Haem is further broken into the iron and biliverdin. While globulin is broken into the amino acid and again recycled.

This bilirubin is circulated in the blood, reaches the liver as an unconjugated bilirubin, and turns into conjugated bilirubin with the help of glucuronyl transferase. This form of bilirubin is ready to add to the bile.

When the bilirubin reaches the large intestine, gut bacteria deconjugate it again and change into urobilinogen. Further oxidation occurs, which is changed into stercobilin, ready to excrete in feces.
If the bilirubin remains accumulated in the body and is not excreted, it turns the eyes and skin yellow.

• Act as a checkpoint:

As the blood from the digestive system reaches the liver through the portal circulation, the hepatocytes strictly monitor the contents of the blood and remove any possible toxic elements before reaching the systemic circulation.

• Drugs Detoxification:

It also chiefly responsible for the metabolism and detoxification of xenobiotics. Biotransformation is considered a significant route for this purpose. Xenobiotics are usually converted from lipophilic form to hydrophilic form through two series of reactions: phase 1 reaction and phase 2 reaction.
These reactions are held in the endoplasmic reticulum of the hepatocytes.

• Conversion of Ammonia into Urea:

Ammonia is a toxic compound that forms in the body due to the metabolism of amino acids and other compounds having ammonia.
The urea cycle converts excess ammonia in the body into urea, which occurs in the mitochondria of the hepatocytes of the liver.
When added to the bloodstream and reaches the kidneys, this urea is filtered out by the nephron and excreted in the urine.

• A storage site for iron:

The liver is an active site for storing iron in the form of active cores of ferritin shells and as hemosiderin (insoluble product of ferritin).

When the carbohydrate-rich food enters the digestive system and begins to digest, blood glucose levels spike up simultaneously, and insulin is released and acts on the liver’s hepatocytes and stimulates glycogen synthase.
Glucose molecules begin to form the chain of glycogen. This process is sped up after the meal, and more glycogen chains form in the liver.
After some time, when food is completely digested and the blood glucose level drops, the body requires energy. Hence, the glycogen phosphorylase, an enzyme responsible for the glycogen chain breakage, becomes a glucose molecule again and provides energy to the body for 6-8 hours.

• Production of vital proteins:

The liver is an active site for synthesizing vital proteins, including prothrombins, fibrinogens, albumins, immunoglobulin, etc.
It also has reticuloendothelial cells, which are responsible for this.
Prothrombin and fibrinogens are coagulation factors responsible for the blood clotting process.
Albumins are the proteins responsible for maintaining the isotonic environment of the blood.

• Fight against infections:

The liver works as a soldier of the body’s immune system through the action of Kupffer cells. These fixed macrophages from the mononuclear phagocytic system work in coordinating macrophages found in the spleen and lymph nodes.
Kufpper cells play a significant role in capturing and destroying foreign bodies like bacteria, viruses, parasites, fungi, etc.
A tremendous amount of blood travels through the portal circulation, so the liver cleans the blood very efficiently.

• Warehouse for proteins and vitamins:

The liver provides a warehouse facility for various essential proteins and vitamins received from the blood travel through the portal circulation. The liver extracts and stores these to ensure an uninterrupted supply to the body.
Hepatocytes also store vitamins A, D, E, and K, as well as vitamin B12, iron, and copper.

Diagnostic Measures:

LFTs are also known as liver panels. It is the group of blood tests that examine different enzymes, compounds, and proteins synthesized in the liver, and these are beneficial to check the rate of liver cell damage (if any) and the overall health of the liver. These include

• Aspartate transaminase (AST),
• Alanine transaminase (ALT),
• Serum bilirubin,
• Alkaline phosphatase (A.L.P.),
• Gamma-glutamyltranspeptidase (G.G.T.),
• Albumin and total protein,
• Prothrombin time (P.T.),
• L.Lactate dehydrogenase (L.D.),

IMAGING TECHNIQUES:

It includes:

• Ultrasonography,
• Computed tomography (C.T.) scan,
• Magnetic resonance imaging (M.R.I.),

SURGICAL TECHNIQUES:

• Liver biopsy.
• Transjugular liver biopsy.
• Laparoscopic liver resection.

CONCLUSION:

In conclusion, the liver is a remarkable and vital organ crucial in keeping our bodies healthy. It acts like a hardworking filter, cleaning our blood, processing nutrients, and breaking down harmful substances. We’ve learned that taking good care of our liver is essential for our overall well-being.

By eating a balanced diet, staying hydrated, limiting alcohol consumption, and avoiding risky behaviors, we can help our liver function at its best. Remember, A healthy liver means a healthier you. So, let’s be kind to our livers and give them the love and care they deserve. After all, they work tirelessly behind the scenes to keep us feeling our best!