A liver sinusoid is a type of
capillary
A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the bod ...
known as a sinusoidal capillary, discontinuous capillary or sinusoid, that is similar to a
fenestrated capillary, having discontinuous
endothelium
The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the ve ...
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
The portal vein or hepatic portal vein (HPV) is a blood vessel that carries blood from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver. This blood contains nutrients and toxins extracted from digested contents. Approx ...
.
The liver sinusoid has a larger caliber than other types of capillaries and has a lining of specialised endothelial cells known as the
liver sinusoidal endothelial cell
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 ...
s (LSECs), and
Kupffer cells.
The cells are porous and have a scavenging function.
The LSECs make up around half of the non-parenchymal cells in the liver and are flattened and fenestrated.
LSECs have many fenestrae that gives easy communication between the sinusoidal lumen and the
space of Disse. They play a part in filtration,
endocytosis
Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material. ...
, and in the regulation of blood flow in the sinusoids.
The Kupffer cells can
take up and destroy foreign material such as
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
.
Hepatocytes
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:
* Protein synthesis
* Protein storage
* Transformation of carbohydrates
* Synthesis of cholesterol, ...
are separated from the sinusoids by the
space of Disse.
Hepatic stellate cells are present in the space of Disse and are involved in
scar formation in response to liver damage.
Defenestration happens when LSECs are lost rendering the sinusoid as an ordinary capillary. This process precedes
fibrosis
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 perma ...
.
Endothelium
The liver sinusoidal endothelial cells are cultured for a variety of research purposes. The utility of these cells are of particular interest. One problem to overcome is the reversing of
cellular differentiation
Cellular differentiation is the process in which a stem cell alters from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular ...
that has made these cells highly specialized phenotypically ''
in vitro
''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology a ...
''.
Additional images
File:Sinusoid.JPG, Human liver sinusoid
File:Gray1092.png, A single lobule of the liver of a pig. X 60.
References
External links
*
* - "Liver, Gall Bladder, and Pancreas: liver, classic lobule"
* - "Ultrastructure of the Cell: hepatocytes and sinusoids, sinusoid and space of Disse"
Histology at anhb.uwa.edu.au
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Veins of the torso
Liver anatomy