The Liver: Structure and Functions

Definition:

The liver is a sizable organ in the abdomen that is responsible for many vital bodily processes, including filtering blood. It also qualifies as a gland because it produces essential chemicals for the body. The liver can be harmed by some conditions and ways of living, but there are many ways to safeguard this important organ.

The liver is the most important gland inside the human frame. About 3-5% of body weight. An adult's liver weighs about 1.5-2.00 kg. Its weight is about 200 grams less in women. It is also located outside the digestive tract. Main metabolic site of proteins, carbohydrates, and fats.

Location:

Positioned within the top part of the abdominal cavity simply underneath the diaphragm, the liver inside the human frame is situated on the right side of the stomach.

Structure:

The liver is a reddish-brown triangular organ, which is covered by a connective tissue called Glisson's capsule. The liver consists of four incomplete segments. The liver is divided into the right lobe and left lobe by mesentery called the falciform ligament. The right lobe is six instances large than the left lobe. The right lobe is divided digitally into 2 lobes called quadrate and caudate. The pear-shaped gall bladder is attached below the quadrate lobe. Bile (bile) synthesized in the liver is discharged through the common liver or hepatic duct and temporarily stored in the gallbladder. The gallbladder opens into the duodenum, the primary part of the small gut, through the common bile duct. Bile from the gallbladder mixes with food in the duodenum and participates in digestion. Dogs and horses do not have gallbladders.

The liver is a secretory and excretory organ. Each lobe (segment) of the liver consists of numerous lobules or acinus (subdivisions). At the center of each lobule is a central vein. Each lobule is again composed of cystic ducts containing numerous hepatic cells (hepatocytes). These cells are arranged in a row from the center to the periphery like the spokes of the circle. Between the lobules are the portal vein, hepatic artery, bile duct, etc. Each common hepatic duct is the cell row are sinusoids and on the other are bile canaliculi. The sinusoids contain phagocytic Kupffer cells. The right and left hepatic ducts (hepatic ducts) coming from the proper and left facets of the liver join together to shape the commonplace hepatic duct. It joins with the cystic duct of the gallbladder to form the gallbladder, which expands downward and posteriorly and joins the pancreatic duct to form the ampulla of vater or hepatopancreatic ampulla and opens into the duodenum.

Function: 

The liver secretes bile and stores it in the gallbladder and helps in the absorption of fatty substances. Moreover, it helps transport food such as carbohydrates, proteins, and vitamins into the bloodstream after digestion.

 

Storage and metabolic role of the liver:

The liver is the largest and most important digestive gland in the human body, which functions as well-equipped biochemistry. All blood from the stomach and acid enters the liver. The liver chemically changes nutrients from the blood into usable material and stores them until needed. Apart from this, the liver also performs functions related to various complications and excretion. Scientists have identified about 500 types of biochemical reactions in the liver. Because various types of biochemical reactions are completed in the liver, scientists have identified the liver as a well-equipped organic laboratory or chemical laboratory. It's miles the principal metabolic site of all sorts of vitamins, consisting of carbohydrates, proteins, and fats. In the liver, food particles and drugs are broken down into relatively small particles, which the body can easily absorb. The liver is also called the graveyard of dead cells and the active shelter of the ocean of life.

Storage Functions of Liver:

1. Glycogen storage:

The liver is the main storage center of the body. The liver gets glucose from the small intestine through the hepatic portal vein. In times of increased blood glucose, the liver converts excess glucose into glycogen via the process of glycogenesis, storing it inside its tissues. The liver is capable of storing approximately 100 grams of glycogen.  

Insulin secreted from the islets of Langerhans stimulates the process. Insulin lowers the amount of glucose in the blood. When blood sugar levels drop, glycogen is converted back into glucose. As a result, blood sugar levels are controlled. When blood glucose levels rise due to a lack of insulin, excess blood glucose is excreted through urine. This disease is called diabetes mellitus. Generally, when the blood glucose level is too low, it is called hypoglycemia. 

Again, if the level of glucose in the blood increases too much then it is called hyperglycemia. Normal blood glucose level < 7.8 mmol / l 2. Storage of Fat and Amino acid: Excess lipids in the blood are stored as glycolipids in the liver. Once more, for the sugars that can not be used inside the frame or saved as glycogen, the liver turns the extra sugars (glucose) into fats and shops them. Unnecessary and excess amino acids are converted in the liver to urea on the one hand and fat on the other. Fats and amino acids are converted into usable glucose as needed by the body.

  

3. Storage of Vitamins:

Liver stores fat-soluble nutrients (A, D, E, K), water-soluble nutrients cyanocobalamin (B12), and folic acid. B12 and folic acid are had to make purple blood cells inside the bone marrow.

4. Storage of Bile:

The liver produces bile in the gall bladder and aids in fat digestion by causing emulsification of fatty foods.

5. Storage of Blood:

Blood vessels from the spleen and arms join to form the hepatic portal vein. Although blood flows continuously through the liver, its blood vessels and hepatic 'portal veins' act as reservoirs holding large amounts of blood. When the blood volume increases (i.e. when blood is taken for special needs), the hepatic vein along with other veins dilates to accommodate the excess blood. The liver can store about 1500 cubic cm of blood. Kupffer cells gift within the liver eliminate numerous microorganisms (consisting of bacteria, protozoa, fungi, and so on.) from the blood in a filtering process. In addition to the liver's dead cells, dying red blood cells, cancer cells, and cellular wastes are removed from the blood.

6. Storage of Minerals:

Hemoglobin produced by the breakdown of red blood cells is converted into heme and globin through the Kupffer cells of the liver. The iron part of heme is stored as ferritin. Also, minerals are vital for a wholesome frame, consisting of copper, zinc, cobalt, molybdenum, potassium, and many others. Are saved in minerals.

 

Metabolic Functions of Liver.

 1. Carbohydrate metabolism:

The central organ in charge of regulating blood sugar levels is the liver. Extra glucose can be stored as glycogen in the liver after food consumption. The release of insulin causes this. The liver stores about 100g of glycogen, while skeletal muscle holds 300g. The steps involved in glycogen synthesis are as follows:

• Glucokinase, additionally known as skeletal muscle Glucokinase and hexokinase, converts glucose to glucose-6-P.
• Phosphoglucomutase transforms glucose-6-P into glucose-1-P.
• Then, glucose-1-P is changed into UDP-glucose.
• Finally, either glycogen synthase or branching enzymes add UDP-glucose to the glycogen chain within the liver.

2. Protein metabolism:

Deamination:

Liver deaminase from unused and excess amino acids. Deamination in the presence of enzymes produces keto acids and amino groups (NH2). Keto acids are used in the Krebs cycle to produce energy. The amino group combines with hydrogen ions and transforms to produce ammonia which is highly toxic and harmful to the body. If it accumulates in the body, it can cause human death.

Production of urea:

In the liver in the ornithine cycle, ammonia combines with CO2 produced in sugar metabolism to form urea [CO(NH3)2]. Urea enters the kidneys through the bloodstream and is excreted from the frame in the form of urine from the kidneys.

Production of amino acid:

The liver takes part in the transamination process i.e. by transfer of amino group (-NH2) from one amino acid to another organic acid.

Production of plasma protein by synthesizing acid:

Most plasma proteins such as albumin, globulin, prothrombin, fibrinogen, etc. are synthesized from the amino acids of the liver. These proteins (especially albumin) carry calcium, bile salts, and some steroid hormones through the blood. Liver-produced plasma proteins prothrombin and fibrinogen are essential blood coagulation factor, which helps blood to clot. Globulins protect the immune system.

3. Fat metabolism:

• The fat absorbed from the arms reaches the liver and becomes fat.
• Synthesizes fats from carbohydrates and proteins.
• The liver synthesizes phospholipids, cholesterol, lipoproteins, and so on.
• Within the liver, strength is produced in the form of ATP as a result of the combustion or oxidation of fat in aggregate with oxygen.
• Oxidation of glycerol and fatty acids takes place within the liver, ensuing in the synthesis of ketone bodies.
• Glucose is produced within the system of gluconeogenesis from saved fat in the absence of sugar.

4. Nucleic acid metabolism:

Purine and pyrimidine nucleotides are synthesized within the liver with the assistance of amino acids, glutamine, and lots of others. Over again, the metabolism of purine inside the liver produces uric acid and the metabolism of pyrimidine produces urea. Within the liver, glycocholic acid and taurocholic acid are synthesized from the amino acids glycine and taurine respectively.

5. Vitamin metabolism:

It causes the synthesis of vitamin A from beta-carotene. The liver produces V-A with the help of vitamin K. 

6. Blood-related functions: 

In the fetal state, it creates red blood cells. Destroys red blood cells when full. The liver aids in blood clotting by producing prothrombin and fibrinogen. Mast cells secrete heparin to prevent blood from pooling in the bloodstream. Hemoglobin in RBC breaks down to form bilirubin and biliverdin. The liver absorbs iron to form hemoglobin.

7. Function of excretion:

The liver removes various metals, toxins, bacteria, unnecessary and excess drugs from the body through bile. In addition, the liver produces various types of antibodies. 

8. Heat control:

Liver chemical reactions absorb more heat and body heat Keep under control.

9. Cholesterol and enzyme production: 

Cholesterol is produced in the liver after various processes after consuming food rich in cholesterol or fat. Ldl cholesterol plays a unique position in complications related to thrombosis and stroke (cerebral thrombosis). Further, the liver produces the catalase enzyme that breaks down the toxic hydrogen peroxide saved within the cells into water and oxygen. Catalase also breaks down toxins within the human liver.

10. Bile production: 

Liver cells (hepatocytes) constantly secrete bile and store it in the gallbladder. Liver cells secrete steroids from bile salts such as sodium glycocholate (sodium glycocholate), and synthesize sodium taurocholate. Production and secretion of the liver as a digestive organ are important functions.

11. Breakdown of Hormones:

The liver destroys almost all hormones more or less. The liver increases the blood pressure in the body by synthesizing the hormone called angiotensinogen or by activating the enzyme renin (renin) secreted by the kidneys.

12. Removal of toxins or poisons (Detoxification):

Liver cells secrete steroids from bile salts such as sodium glycocholate (sodium glycocholate), which synthesizes sodium taurocholate. As a digestive organ, the production and secretion of bile is an important function of the liver. All substances that cause toxicity in the body when the substance accumulates excessively are called toxins or poisons.  This poison is neutralized by biochemical processes inside the cells. The juice secreted by the liver is called bile or pitta. Bile is stored in the gallbladder. It is a yellowish liquid.

Bile:

It is bitter in taste, and slightly alkaline (pH 8.0-8.6): Relative importance: 1.010-1.011. The liver produces about 500-1000 milliliters of bile per day.

Constituents of bile:

1. Water: 89%-98%

2. Solids: 2%-11%

(a) Inorganic Matter: 0.7% - 0.8%, various salts of sodium, potassium, and calcium.

(b) Organic matter: 1.3% - 10.2%

(i) Gallbladde saltr: sodium taurocholate and sodium glycocholate

(ii) Bile pigment: bile bilirubin, biliverdin.

(iii)Bile acid: cholic acid, lithocholic acid.

(c) Other substances: cholesterol, lecithin, fatty acids, mucin, nucleoprotein, mucus, etc.

The function of bile:

 The functions of bile are as follows:

1. Digestion: 

Gallbladder digests food into 2030 grains by emulsification. Functions of Bile Bile is an essential substance for life. It aids in digestion by activating the important bile fat-digesting enzyme lipase, even though it lacks digestive enzymes.

2. Absorption: 

Gallbladder is essential for the absorption of fats, iron, and calcium, fat-soluble, vitamins (vitamins A, D, E, and K).

3. Excretory:

Excretory products such as copper, zinc, lead, mercury, toxins, bile acids, cholesterol, bacteria, lecithin etc. are removed from the body through excretory bile.

4. Wastage removal action: 

Bile salts stimulate peristalsis; It softens the bowels to facilitate stool evacuation.

5. pH regulation: 

HCI balances pH by neutralizing excess alkalinity in bile and aids in various enzyme activities by balancing the pH of the bile duodenum.

6. Buffer and Lubricant: Bile mucin acts as a buffer and lubricant.