A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in:
Portal hypertension is defined as increased portal venous pressure, with a hepatic venous pressure gradient greater than 5 mmHg. Normal portal pressure is 1–4 mmHg; clinically insignificant portal hypertension is present at portal pressures 5–9 mmHg; clinically significant portal hypertension is present at portal pressures greater than 10 mmHg. The portal vein and its branches supply most of the blood and nutrients from the intestine to the liver.
Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of permanent scar tissue.
Fatty liver disease (FLD), also known as hepatic steatosis and steatotic liver disease (SLD), is a condition where excess fat builds up in the liver. Often there are no or few symptoms. Occasionally there may be tiredness or pain in the upper right side of the abdomen. Complications may include cirrhosis, liver cancer, and esophageal varices.
Kupffer cells, also known as stellate macrophages and Kupffer–Browicz cells, are specialized cells localized in the liver within the lumen of the liver sinusoids and are adhesive to their endothelial cells which make up the blood vessel walls. Kupffer cells comprise the largest population of tissue-resident macrophages in the body. Gut bacteria, bacterial endotoxins, and microbial debris transported to the liver from the gastrointestinal tract via the portal vein will first come in contact with Kupffer cells, the first immune cells in the liver. It is because of this that any change to Kupffer cell functions can be connected to various liver diseases such as alcoholic liver disease, viral hepatitis, intrahepatic cholestasis, steatohepatitis, activation or rejection of the liver during liver transplantation and liver fibrosis. They form part of the mononuclear phagocyte system.
Plasminogen activator inhibitor-1 (PAI-1) also known as endothelial plasminogen activator inhibitor is a protein that in humans is encoded by the SERPINE1 gene. Elevated PAI-1 is a risk factor for thrombosis and atherosclerosis.
Hypervitaminosis A refers to the toxic effects of ingesting too much preformed vitamin A. Symptoms arise as a result of altered bone metabolism and altered metabolism of other fat-soluble vitamins. Hypervitaminosis A is believed to have occurred in early humans, and the problem has persisted throughout human history. Toxicity results from ingesting too much preformed vitamin A from foods, supplements, or prescription medications and can be prevented by ingesting no more than the recommended daily amount.
A myofibroblast is a cell phenotype that was first described as being in a state between a fibroblast and a smooth muscle cell.
The perisinusoidal space is a space between a hepatocyte, and a sinusoid in the liver. It contains the blood plasma. Microvilli of hepatocytes extend into this space, allowing proteins and other plasma components from the sinusoids to be absorbed by the hepatocytes. Fenestration and discontinuity of the sinusoid endothelium facilitates this transport. The perisinusoidal space also contains hepatic stellate cells, which store vitamin A in characteristic lipid droplets.
A liver sinusoid is a type of capillary known as a sinusoidal capillary, discontinuous capillary or sinusoid, that is similar to a fenestrated capillary, having discontinuous endothelium that serves as a location for mixing of the oxygen-rich blood from the hepatic artery and the nutrient-rich blood from the portal vein.
Hepatic lipase (HL), also called hepatic triglyceride lipase (HTGL) or LIPC (for "lipase, hepatic"), is a form of lipase, catalyzing the hydrolysis of triacylglyceride. Hepatic lipase is coded by chromosome 15 and its gene is also often referred to as HTGL or LIPC. Hepatic lipase is expressed mainly in liver cells, known as hepatocytes, and endothelial cells of the liver. The hepatic lipase can either remain attached to the liver or can unbind from the liver endothelial cells and is free to enter the body's circulation system. When bound on the endothelial cells of the liver, it is often found bound to heparan sulfate proteoglycans (HSPG), keeping HL inactive and unable to bind to HDL (high-density lipoprotein) or IDL (intermediate-density lipoprotein). When it is free in the bloodstream, however, it is found associated with HDL to maintain it inactive. This is because the triacylglycerides in HDL serve as a substrate, but the lipoprotein contains proteins around the triacylglycerides that can prevent the triacylglycerides from being broken down by HL.
Cytoglobin is the protein product of CYGB, a human and mammalian gene.
Cellular senescence is a phenomenon characterized by the cessation of cell division. In their experiments during the early 1960s, Leonard Hayflick and Paul Moorhead found that normal human fetal fibroblasts in culture reach a maximum of approximately 50 cell population doublings before becoming senescent. This process is known as "replicative senescence", or the Hayflick limit. Hayflick's discovery of mortal cells paved the path for the discovery and understanding of cellular aging molecular pathways. Cellular senescence can be initiated by a wide variety of stress inducing factors. These stress factors include both environmental and internal damaging events, abnormal cellular growth, oxidative stress, autophagy factors, among many other things.
Integrin alpha-11 is a protein that, in humans, is encoded by the ITGA11 gene.
The liver is a major metabolic organ exclusively found in vertebrate animals, which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and various other biochemicals necessary for digestion and growth. In humans, it is located in the right upper quadrant of the abdomen, below the diaphragm and mostly shielded by the lower right rib cage. Its other metabolic roles include carbohydrate metabolism, the production of hormones, conversion and storage of nutrients such as glucose and glycogen, and the decomposition of red blood cells.
Pancreatic stellate cells (PaSCs) are classified as myofibroblast-like cells that are located in exocrine regions of the pancreas. PaSCs are mediated by paracrine and autocrine stimuli and share similarities with the hepatic stellate cell. Pancreatic stellate cell activation and expression of matrix molecules constitute the complex process that induces pancreatic fibrosis. Synthesis, deposition, maturation and remodelling of the fibrous connective tissue can be protective, however when persistent it impedes regular pancreatic function.
Liver cytology is the branch of cytology that studies the liver cells and its functions. The liver is a vital organ, in charge of almost all the body’s metabolism. Main liver cells are hepatocytes, Kupffer cells, and hepatic stellate cells; each one with a specific function.
Liver regeneration is the process by which the liver is able to replace damaged or lost liver tissue. The liver is the only visceral organ with the capacity to regenerate. The liver can regenerate after partial hepatectomy or injury due to hepatotoxic agents such as certain medications, toxins, or chemicals. Only 51% of the original liver mass is required for the organ to regenerate back to full size. The phenomenon of liver regeneration is seen in all vertebrates, from humans to fish. The liver manages to restore any lost mass and adjust its size to that of the organism, while at the same time providing full support for body homeostasis during the entire regenerative process. The process of regeneration in mammals is mainly compensatory growth or hyperplasia because while the lost mass of the liver is replaced, it does not regain its original shape. During compensatory hyperplasia, the remaining liver tissue becomes larger so that the organ can continue to function. In lower species such as fish, the liver can regain both its original size and mass.
Perilipin 5, also known as Oxpatperilipin 5 or PLIN5, is a protein that belongs to perilipin family. This protein group has been shown to be responsible for lipid droplet's biogenesis, structure and degradation. In particular, Perilipin 5 is a lipid droplet-associated protein whose function is to keep the balance between lipolysis and lipogenesis, as well as maintaining lipid droplet homeostasis. For example, in oxidative tissues, muscular tissues and cardiac tissues, PLIN5 promotes association between lipid droplets and mitochondria.
Liver sinusoidal endothelial cells (LSECs) form the lining of the smallest blood vessels in the liver, also called the hepatic sinusoids. LSECs are highly specialized endothelial cells with characteristic morphology and function. They constitute an important part of the reticuloendothelial system (RES).
