Hepatocyte

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Hepatocyte

Hepatocytes make up 70-80% of the cytoplasm

Cytoplasm

The cytoplasm is the part of a Cell that is enclosed within the plasma membrane. In eukaryote cells the cytoplasm contains organelles, such as mitochondrion, that are filled with liquid kept separate from the rest of the cytoplasm by biological membranes....
ic mass of the liver

Liver

The liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, a few of which are detoxification, protein synthesis, and production of biochemicals necessary for digestion....
. These cells are involved in protein synthesis

Protein synthesis

Protein synthesis is the creation of proteins using DNA and RNA. Proteins can often be synthesized directly from genes by Translation mRNA. When a protein is harmful and needs to be available on short notice or in large quantities, a protein precursor is produced....
, protein storage and transformation of carbohydrate

Carbohydrate

Carbohydrates or saccharides are the most abundant of the four major classes of biomolecules. They fill numerous roles in living things, such as the storage and transport of energy and structural components ....
s, synthesis of cholesterol

Cholesterol

Cholesterol is a lipidic, waxy alcohol found in the cell membranes and transported in the blood plasma of all animals. It is an essential component of mammalian cell membranes where it is required to establish proper membrane permeability and membrane fluidity....
, bile salts and phospholipid

Phospholipid

File:Phospholipid.svgFile:phospholipid_structure.pngFile:Phosphatidyl-Choline.svgPhospholipids are a class of lipids and are a major component of all cell membranes....
s, and detoxification, modification and excretion of exogenous and endogenous substances. The hepatocyte also initiates the formation and secretion of bile

Bile

Bile or gall is a bitter yellow or green fluid secreted by hepatocytes from the liver of most vertebrates. In many species, bile is stored in the gallbladder between meals and upon eating is discharged into the duodenum where the bile aids the process of digestion of lipids....
.

tocytes display an eosinophilic

Eosinophilic

Eosinophilic means loves eosin, and refers to the staining of certain Biological tissue, cell , or organelles after they have been washed with eosin, a dye....
cytoplasm, reflecting numerous mitochondria, and basophilic

Basophilic

Basophilic is a technical term used by Histology. It describes the microscopic appearance of cell s and Biological tissues, as seen down the microscope, after a histological section has been stained with a basic dye....
stippling due to large amounts of rough endoplasmic reticulum and free ribosomes.

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Hepatocyte histology

Hepatocytes display an eosinophilic

Eosinophilic

Basophilic

Lipofuscin

Lipofuscin is the name given to finely granular yellow brown pigment Granule composed of lipid-containing residues of lysosomal digestion. It is considered one of the aging or "wear and tear" pigments; found in the liver, kidney, heart muscle, adrenals, nerve cells, and ganglion cells....
granules are also observed (with increasing age) together with irregular unstained areas of cytoplasm; these correspond to cytoplasmic glycogen

Glycogen

Glycogen is a polysaccharide of glucose which functions as the secondary short term energy storage in animal cells. It is made primarily by the liver and the muscles, but can also be made by the brain and stomach....
and lipid

Lipid

Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
stores removed during histological preparation. The average life span of the hepatocyte is 5 months; they are able to regenerate.

Hepatocyte nuclei

Cell nucleus

In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in all eukaryote cell ....
are round with dispersed chromatin

Chromatin

Chromatin is the complex combination of DNA, RNA, and protein that makes up chromosomes. It is found inside the cell nucleus of Eukaryote cell , and within the nucleoid in prokaryotic cells....
and prominent nucleoli. Anisokaryosis is common and reflects tetraploidy & polyploidy

Polyploidy

Polyploidy occurs in biological cell and organisms when there are more than two Homologous Chromosomes sets of chromosomes.Polyploidy is a state different from most organisms which are normally diploid meaning they have only two sets of chromosomes - one set inherited from each parent; polyploidy may occur due to abnormal cell division....
, a normal feature of over 50% of hepatocytes. Binucleate cells are also common. Hepatocytes are organised into plates separated by vascular channels (sinusoids

Liver sinusoid

A liver sinusoid is a type of Sinusoid that serve as a location for the oxygen-rich blood from the hepatic artery and the nutrient-rich blood from the portal vein....
), an arrangement supported by a reticulin (collagen type III) network. The hepatocyte plates are one cell thick in mammals and two cells thick in the chicken. Sinusoids display a discontinuous, fenestrated endothelial cell lining. The endothelial cells have no basement membrane

Basement membrane

The basement membrane is a sheet of cells and fibers that covers two other kinds of cells -- the epithelium, which lines the cavities and surfaces of organs, and the endothelium, which lines the interior surface of blood vessels....
and are separated from the hepatocytes by the space of Disse which drains lymph

Lymph

Lymph is the fluid that is formed as the interstitial fluid. It enters the lymph vessels by filtration. The lymph then travels to at least one lymph node before emptying ultimately into the right or the left subclavian vein, where it mixes back with blood....
into the portal tract lymphatics. Kupffer cells are scattered between endothelial cells; they are part of the reticuloendothelial system

Reticuloendothelial system

The reticuloendothelial system , part of the immune system, consists of the phagocytosis cells located in reticular connective tissue, primarily monocytes and macrophages....
and phagocytose spent erythrocytes. Stellate (Ito) cells store vitamin A

Vitamin A

Vitamin A, a bi-polar molecule formed with bi-polar covalent bonds between carbon and hydrogen, is linked to a family of similarly shaped molecules, the retinoids, which complete the remainder of the vitamin sequence....
and produce extracellular matrix

Extracellular matrix

In biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal Cell in addition to performing various other important functions....
and collagen

Collagen

Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content....
; they are also distributed amongst endothelial cells but are difficult to visualise by light microscopy.

Hepatocytes are an important physiological example for evalutation of both biological and metabolic effects of xenobiotics. Hepatocytes are available for purchase commercially. They are separated from the liver by collagenase digestion, which is a two step process. In the first step, the liver is placed in an isotonic

Isotonic

The term isotonic may refer to;* Isometric exercise and Weight training#Isotonic, Isometric and Plyometric exercises* Isotonic for the term associated with muscle contraction...
solution, in which calcium is removed to disrupt cell-cell tight junctions by the use of a calcium chelating agent. Next, a solution containing collagenase is added to separate the hepatocytes from the liver parenchyma

Parenchyma

Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, from Greek language parenkhuma, visceral flesh, from parenkhein, to pour in beside : para-, beside + en-, in + khein, to pour....
. This process creates a suspension of hepatocytes, which can be cultured and plated on 96 well plates for immediate use, or cryopreserved by freezing. They do not proliferate in culture. Hepatocytes are intensely sensitive to damage during the cycles of cryopreservation including freezing and thawing. Even after the addition of classical cryoprotectants there is still damage done while being cryopreserved.

Protein Synthesis

The hepatocyte is a cell

Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
in the body

Body

With regard to organism, a body is the integral physical material of an individual. "Body" often is used in connection with appearance, health issues and death....
that manufactures serum albumin

Serum albumin

Serum albumin, often referred to simply as albumin, is the most abundant plasma protein in humans and other mammals. Albumin is essential for maintaining the osmotic pressure needed for proper distribution of body fluids between intravascular compartments and body tissues....
, fibrinogen, and the prothrombin group of clotting factors. It is the main site for the synthesis of lipoprotein

Lipoprotein

A lipoprotein is a biochemistry assembly that contains both proteins and lipids. The lipids or their derivatives may be covalently or non-covalently bound to the proteins....
s, ceruloplasmin

Ceruloplasmin

Ceruloplasmin is officially known as ferroxidase or iron:oxygen oxidoreductase. It is the major copper-carrying protein in the blood, and in addition plays a role in iron metabolism....
, transferrin

Transferrin

Transferrin is a blood plasma protein for iron ion delivery that, in humans, is encoded by the TF gene. Transferrin is a glycoprotein, which binds iron very tightly but reversibly....
, complement

Complement system

The complement system is a biochemical cascade that helps clear pathogens from an organism. It is part of the larger immune system that is not adaptable and does not change over the course of an individual's lifetime; as such it belongs to the innate immunity....
and glycoprotein

Glycoprotein

Not to be confused with peptidoglycan or proteoglycan.Glycoproteins are proteins that contain oligosaccharide chains covalently attached to their Peptide side-chains....
s. Hepatocytes manufacture their own structural proteins and intracellular enzyme

Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s.

Synthesis of proteins is undertaken by the rough endoplasmic reticulum (RER), and both the rough and smooth endoplasmic reticulum (SER) are involved in secretion of the proteins formed. The endoplasmic reticulum

Endoplasmic reticulum

The endoplasmic reticulum is a eukaryote organelle that forms an interconnected network of tubules, vesicle , and cisternae within cell . The lacey membranes of the endoplasmic reticulum were first seen by Keith R....
(ER) is involved in conjugation of proteins to lipid and carbohydrate moieties synthesized by, or modified within, the hepatocytes.

Carbohydrate metabolism

The liver

Liver

Carbohydrate

Apoprotein

Apoprotein can refer to:*Apoenzyme, the protein part of an enzyme without its characteristic prosthetic group.*Apolipoprotein, a lipid-binding protein that is a constituent of the plasma lipoprotein....
s with which they then assemble and export lipoproteins (VLDL

Very low density lipoprotein

Very low-density lipoprotein is a type of lipoprotein made by the liver. VLDL is one of the five major groups of lipoproteins which enable fats and cholesterol to move within the water based solution of the blood stream....
, HDL

High density lipoprotein

High-density lipoproteins is one of the 5 major groups of lipoproteins which enable lipids like cholesterol and triglycerides to be transported within the water based blood stream....
).

The liver is also the main site in the body for gluconeogenesis

Gluconeogenesis

Gluconeogenesis is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactic acid, glycerol, and glucogenic amino acids....
, the formation of carbohydrates from precursors such as alanine

Alanine

Alanine is an a-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 proteinogenic amino acids, i.e. the building blocks of proteins....
, glycerol

Glycerol

Glycerol is a chemical compound also commonly called glycerin or glycerine. It is a colorless, odorless, Viscosity liquid that is widely used in pharmaceutical formulations....
and oxaloacetate.

Lipid metabolism

The liver receives many lipid

Lipid

Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
s from the systemic circulation and metabolizes chylomicron

Chylomicron

Chylomicrons are large lipoprotein that transport dietary lipids from the intestines to other locations in the body. Chylomicrons are one of the 5 major groups of lipoproteins which enable fats and cholesterol to move within the water based solution of the blood stream....
remnants. It also synthesizes cholesterol

Cholesterol

Acetate

An acetate, or ethanoate, is either a salt or ester of acetic acid.In chemistry, the abbreviation Ac refers to the acetyl group. The anion and the functional group may be written as -OAc and AcO-, or OAc respectively....
and then further synthesizes bile salts. The liver is the sole site of formation of bile salts.

Detoxification

These liver cells have the ability to metabolize, detoxify, and inactivate exogenous compounds such as drugs

Medication

A pharmaceutical drug, also referred to as medicine or medicament, can be loosely defined as any substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease....
(drug metabolism

Drug metabolism

Drug metabolism is the metabolism of Medication, their biochemical modification or degradation, usually through specialized Enzyme systems. This is a form of xenobiotic metabolism....
) and insecticide

Insecticide

An insecticide is a pesticide used against insects in all developmental forms. They include ovicides and larvicides used against the Egg and larvae of insects respectively....
s, and endogenous compounds such as steroid

Steroid

A steroid is a terpenoid lipid characterized by a carbon skeleton with four fused rings, generally arranged in a 6-6-6-5 fashion.Steroids vary by the functional groups attached to these rings and the oxidation state of the rings....
s.

The drainage of the intestinal venous blood

Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
into the liver

Liver

Homeostasis

Homeostasis is the property of a system, either open system or closed system, that regulates its internal environment and tends to maintain a stable, constant condition....
and protect the body against ingested toxins.

One of the detoxifying functions of hepatocytes is to modify ammonia into urea

Urea

Urea is an organic compound with the chemical formula 2carbonoxygen.Urea is also known by the International Nonproprietary Name carbamide, as established by the World Health Organization....
for excretion.

Additional images

External links

- "Ultrastructure of the Cell: hepatocytes and sinusoids"