Cells of Liver
There are 4 basic cell types that reside in the liver:
- the hepatocyte
- the stellate fat storing cell
- the Kupffer cell
- the liver endothelial cell.
These so-called resident cells control many of the key functions in the liver, as well as its response to injury.
Hepatocytes make up about 80% of the cells in the liver.
- are large polyhedral epithelial cells, with large round centrally located nuclei (2 or more)
- grouped in interconnected plates that are arranged into thousand of small polyhedral lobules
- store glucose in the form of glycogen , also vitamin B12, folic acid and iron
- participate in the turnover and transport of lipids.
- synthesize some of the plasma proteins (albumin, α and β globulins, prothrombin, fibrinogen
- metabolize/detoxify fat
- participate in the turnover of steroid hormones.
- regulates cholesterol level
- secrete bile (up to 1 liter per day)
Hepatic stellate fat storing cells ( ITO cells )
- reside in close proximity to the hepatocyte (in the perisinusoidal space, not in lumen!)
- store approximately 80% of the body's supply of vitamin A and a variety of other lipids (under normal conditions)
- under conditions of liver injury, activated stellate cells are highly responsive to pro-fibrogenic factors such as transforming growth factor- ß (TGF-ß).
- proliferate in response to factors such as platelet-derived growth factor (PDGF)
- specialized stellate macrophages
- adhere to the sinusoidal endothelium ( in the lumen of the sinusoid), mainly near portal areas (=portal triads)
- clear the blood of ingested bacterial pathogens that may enter portal blood from the gut
- remove aged erythrocytes and free heme for re-use
- act as antigen-presenting cells in adaptive immunity
- secret cytokines and chemokines that recruit and expand the population of other proinflammatory cells in the liver.
Sinusoidal Endothelial Cells
- form the wall of the blood vessels (sinusoids) that carry blood throughout the liver
- form a single layer with spaces between each cell known as fenestra, that allow an efficient flow of essential materials to pass from the blood to
- hepatocytes and vice versa
- are rich in lysosomal enzymes needed for degrading endocytosed material