what is liver?regeneration and embryonic development of liver along with diseases related to liver.


One of the most important organ of the vertebrates goes by the name of liver. In human body liver is located below diaphragm to the upper right of the abdomen and overlies the gallbladder. Liver feels rubbery to touch normally one cannot feel the liver by touching from outside of the body as it is protected by the rib cage. A portion of the liver goes into the upper abdomen as well. Liver accounts for about 20% of the resting total body oxygen consumption. Liver receives a dual blood supply from the hepatic portal vein and the hepatic artery. The hepatic portal vein delivers around 75% of the liver blood supply and carries venous blood drained from the spleen and gastrointestinal tract. Blood flows through the liver sinusoids and empties into the central vein of each lobule which than leaves the liver and drains into the inferior vena cava. It is expected that liver performs about 500 different functions some of the important functions of the liver are as following 
  • production of bile 
  • detoxification of toxins of the body 
  • regulation of the glycogen regulation
  • hormone production
  • decomposition of red blood cells and many more
without a functional liver a person cannot survive. Liver is the heaviest organ and the largest gland in the human body. The weight of liver is about  1.5-1.6 kg with a width of 6 inches it is reddish brown in color it has four lobes of unequal shape and size. The liver is grossly divided into two portions that is the left lobe and a right lobe as observed from the front or upper side but the underside surface shows it to be divided into four lobes and along with the left and right lobe it have a caudate lobe and quadrate lobe. The left lobe is smaller and more flattened than right whereas the right lobe is much larger than the left one.The falciform ligament divides the liver into left and right lobe. Quadrate lobe is an area of the liver situated on the under surface of the medial segment of the left lobe bounded in front by the anterior margin of the liver whereas the caudate lobe is situated upon the posterior superior surface of the liver on the right side of the liver opposite to the tenth and the eleventh thoracic vertebrae. Each lobe is divided into eight segments each segment has about 1000 lobules and these lobules also goes by the name of small lobes each of the lobules has a small duct that flows towards the common hepatic duct. These lobules are the functional unit of the liver. Each lobules is made up of hepatocytes. The lobules are held are held together by a fine dense irregular and fibroelastic connective tissue layer extending from the fibrous capsule covering the entire liver that goes by the name of Glisson's capsule. This capsule is further covered by a peritoneum a membrane is derived from the lining of the abdominal cavity. This helps to hold the liver in place and protects it from any king of physical damage 
Liver has two major sources of blood that are the

  • hepatic artery 
  • portal vein
the portal vein bring nutrient rich blood from the digestive system (gastrointestinal tract) and also from the spleen and Pancreas whereas the hepatic artery carries oxygenated blood from the heart. The blood vessels are divided into small capillaries with each ending in a lobules these lobules are the functional unit of the liver and consist of millions of cells that goes by the name of hepatocytes. In case of deoxygenated blood the deoxygenated blood of the liver is removed through three hepatic veins.compared to the rest of the body liver has a significant amount of blood flowing through it about 13% of body's blood is in the liver at any given time

Only a few organs of the human body have the ability to regenerate and liver is the only visceral organ in the human body that can regenerate such that in case of some lobe some part tissues or cells of liver there is some kind of damage or there is a surgical removal of some parts or section of the liver than that damaged or lost or injured part can grow back to a certain extend as long as minimum of 25% of the tissues of the liver remain and one of the most prominent and astonishing feature of liver is that it can regrow to its previous size and ability without any loss of function during that growth. This regeneration of the liver is controlled and regulated by various growth factors and cytokines some of the important compounds that are responsible or involved in the regeneration of liver are as following 
  • epidermal growth factor
  • insulin
  • nor-adrenaline
  • hepatocyte growth factor
  • transforming growth factor 
  • interleukin 6
During the 8th week of formation of gamete the development of organs starts to take place. The origin of the liver lie in both the ventral position of the foregut endoderm and the constituents of the adjacent septum transversum mesenchyme. A portion of the hepatic diverticulum (liver bud) continues to function as the drainage duct of the liver and a branch from this duct produced the gallbladder. The hepatic endodermal cells undergo a morphological transition from the columnar to pseudostratified resulting in thickening into the early liver bud. Than the liver bud separates into two lobes. The left umbilical vein becomes the ductus venosus and the right vitelline vein become the portal vein the expanding liver bud is than colonized by hematopoietic cells. At the time of birth the liver comprises about 4% of the body weight. But with the growth and maturation of the body liver also grows and mature and wight about 1.4 - 1.6 kg and at such a time it only takes 2.5 - 3.5 %of the body weight. Umbilical vein caries oxygenated nutrient rich blood from the the placenta to the growing fetus whereas the umbilical artery carry deoxygenated nutrient depleted blood from the fetus to the placenta any impairment in blood flow within the cord can be catastrophic event for the fetus. In the fetus the liver does not perform the normal digestive process and filtration of the infant because nutrients are received directly from the mother through placenta. The fetal liver releases some blood stem cells that migrate to the fetal thymus creating T lymphocytes and after birth the formation of blood stem cells shift to the red bone marrow 
 The liver is classed as a gland and associated with many functions as an organ and this organ is still being explored and there are many aspects and things that are still being discovered with respect to functions liver is so diverse that is performs at least 500 different distant roles. This organ is involved in the detoxification of various metabolites but the process of aging the oxidative capacity of the liver decreases and therefore any medication that require oxidation are more likely to accumulate to toxic levels it also produces many biochemical for aiding in digestion such as by the production of bile that is responsible for emulsification of fats in small intestine. If we want to Summarize the functions of the liver than we can conclude the functions performed by the liver as following but one thing to be considered at this point that the functions mentioned below are not just the only functions performed by liver because functionally liver is very diverse as it can perform more than 500 functions and still more are being explored ( in biology there are not a lot of fixed facts because biology is the discussing of life and life is evolving all the time that is the major reason that there are very less or almost equal to zero laws in biology because laws are the constant fact of nature and there is nothing constant in life and nature ) despite this off-topic thing functions of liver are as followng
  • fat metabolisms 
  • synthesis of angiotensinogen 
  • production of albumin 
  • filtration of blood 
  • immunological functions
  • protein metabolism
  • support in blood clothing 
  • vitamin and mineral storage 
  • carbohydrate metabolism
  • bile formation
  • absorption and metabolizing bilirubin
  • and many more 
Any factor that affects the functions of the liver or cause any type of any structural anomalies in it are classified as liver related disorders or liver disorders some of the liver disorders can be treated some cannot be and some can also be fatal there are about more than 100 types of liver disorders some common symptoms that indicates liver problems are such as 
  • dark colored urine 
  • pale colored stool
  • yellowing of skin and eyes
  • enlarged liver
  • stomach discomfort
  • fatigue 
  • vomiting
  • loss of appetite
  • nausea
some of the disease related to liver are as following 

  • autoimmune hepatitis
  • biliary atresia
  • cirrhosis
  • hemochromatosis
  • hepatitis
  • fascioliasis
  • alcoholic liver disease
  • primary sclerosing cholangitis
  • Gilbert's syndrome
autoimmune hepatitis
Auto immune disorder is a genetic disorder in which the immune system instead of attacking any foreign harmful pathogen it starts to attack its own body cells and especially liver cells and in some cases it can induce serious damage to the liver cells exact reason for such a disordered function of the body is still not clear but it is hypothesized that by some of researchers that is caused as a result by the interaction of genes controlling immune system functions or there may be a exposure to particular drugs or any king of viruses untreated autoimmune hepatitis can also lead to cirrhosis and eventually to liver failure symptoms of autoimmune hepatitis varies from person to person whereas some of its prominent and common symptoms are 
  • fatigue
  • abdominal discomfort
  • skin rashes
  • enlarged liver
  • loss of menstrual periods and many more
. There are two different types of autoimmune hepatitis that are 
  • type 1 autoimmune hepatitis 
  • type 2 autoimmune hepatitis
biliary atresia
Biliary atresia that also goes by the name progressive obliterative cholangiopathy is a childhood disease in which one or more bile ducts are abnormally narrow closed or in some cases is absent. This disease may be congenital or acquired biliary atresia mostly occurs in infants it usually occurs due to any type of defect in the early bile duct formation or autoimmunity or may arise in the perinatal period due to an external cause such as hepatotropic virus etc. The only possible and effective treatments for such a disease are operations such as liver transplant or hepatoportoenterostomy.  Symptoms of biliary atresia usually appear between two and six weeks after birth some of the symptoms that infants suffering from this disease shows are as following
  • development of progressive conjugated jaundice
  • dark urine
  • pale white stool
  • malabsorptions of some vitamins such as vitamin k
biliary atresia is further divided into three different types that are as following 
  • type 1 biliary atresia
  • type 2 biliary atresia 
  • type 3 biliary atresia
Whenever liver is injured or damaged due to any reason the liver tries to repair itself  and in the process of healing and repairing itself a scar is formed and a this process continues i.e liver gets damaged it heals itself leaves a scar a time would come when it would  be very difficult for the liver to function in most cases the damaged induced by cirrhosis is irreversible we can also describe cirrhosis as a late stage of scarring of the liver various conditions such as chronic alcohol usage cystic fibrosis fatty liver disease Alagille syndrome autoimmune hepatitis destruction of bile ducts infections  can cause damage the liver and can lead to cirrhosis. Cirrhosis often has no signs until liver is damaged but some symptoms that appears and are noticed are as following 
  • nausea
  • edema 
  • itchy skin
  • yellowish color appearance in skin and ayes
  • redness in the palms of the hands
  • fatigue 
  • loss of appetite and many more 
If anything in the body is in excess amount it can harm the body and disturbs the normal functions of the body similar is the case with the iron when there is increased or excess amount of iron accumulation in the blood it causes hemochromatosis. Normally when we take food there is iron on it this iron gets absorbed by the intestine but in the case of hemochromatosis body absorbs too such iron from the food and there is increased concentration of iron in blood than normal and body has no way to get rid of it so to compensate for the excess amount of iron in blood body tries to store the excess iron in joints and in various organs like liver heart and Pancreas if not treated it damage these organs. There are two types of hemochromatosis that are as following 
  • primary hemochromatosis
  • secondary hemochromatosis
some of the symptoms of hemochromatosis are as following 
  • lethargy
  • pain in joints 
  • coloration of skin to gray color or bronze
  • belly pain
  • foggy memory
  • loss of body hairs and many more
Hepatitis is an inflammation of the liver people that have a chronic hepatitis are also at a risk of liver damage that may also be permanent. Hepatitis is usually caused as a result of some mentioned below reason 
  • viral infections
  • drugs
  • toxic agents 
hepatitis usually shows symptoms such as 
  • liver enlargement 
  • jaundice
  • abdominal pain
  • fatigue
  • sometimes fever and many more
hepatitis are of various types depending upon its genetic makeup whether id caused b a DNA virus or a RNA virus its modes of transmissions and more more aspects like these types of hepatitis are as following 
  • hepatitis A
  • hepatitis B
  • hepatitis C
  • hepatitis D
  • hepatitis E
  • hepatitis F
  • hepatitis G
hepatitis A
                               hepatitis A is transmitted by contact with faces from the infected persons hepatitis A is also known as infectious hepatitis . Hepatitis is more common in developing countries that lack clean drinking water and have poor sanitation system 
hepatitis B 
                                hepatitis B is also called as serum hepatitis hepatitis B is the second major form of hepatitis it is cased by a DNA virus it is transmitted by the exchange of body fluids such as blood serum breast milk saliva from mother to child during child birth in actue attacks of hepatitis B there are symptoms such as fatigue loss of appetite jaundice and many more 

hepatitis C
                                    hepatitis C is also known as the infusion hepatitis and it is a RNA virus which is less serve than the hepatitis A or hepatitis B but it can often lead to chronic liver disease. It is passed from one person to other through infected blood from mother to child during pregnancy or at the time of birth 

This disease is caused by a parasitic invasion of a parasitic worm that is known as liver fluke which can lie dormant for months or even for years it is also considered as tropical disease the scientific name of the parasitic worm liver fluke is Fasciola hepatica whose primary host are either sheep or human (bile ducts) whereas there secondary hosts are snails they have adhesive organs that goes by the name of suckers in case of acute infections immature flukes migrate through the intestinal wall the peritoneal cavity the liver capsule and the parenchyma of the liver before entering the biliary duct where they mature in time of around 3-4 months the usual symptoms shown in this disorder are as following 
  • vomiting 
  • nausea
  • weight loss
  • abdominal pain
  • urticaria and many more
 Gilbert's syndrome
Gilbert's syndrome is a condition  in which there is a increase level of bilirubin levels in the body Gilbert's syndrome is a phenotype effect that is mostly associated with the increased blood bilirubin levels but sometimes also characterized by a mild jaundice due to increased conjugated bilirubin. Gilbert's syndrome is characterized by 70 - 80% reduction in the glucuronidation of the enzyme UGT1A1 which is located on human chromosome 2.


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