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 body: ...

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 vessel ...

that serves as a location for mixing of the oxygen-rich blood from the

hepatic artery The common hepatic artery is a short blood vessel that supplies oxygenated blood to the liver, pylorus of the stomach, duodenum, pancreas, and gallbladder. It arises from the celiac artery and has the following branches: Additional images ...

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. Approxima ...

. 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 cell 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. Ku ...

s. 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 The perisinusoidal space (or space of Disse) is a location in the liver between a hepatocyte and a sinusoid. It contains the blood plasma. Microvilli of hepatocytes extend into this space, allowing proteins and other plasma components from the si ...

. 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. E ...

, 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 among ...

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, b ...

are separated from the sinusoids by the

Hepatic stellate cell Hepatic stellate cells (HSC), also known as perisinusoidal cells or Ito cells (earlier ''lipocytes'' or ''fat-storing cells''), are pericytes found in the perisinusoidal space of the liver, also known as the space of Disse (a small area between th ...

s 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 an ...

''.

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
{{Authority control Veins of the torso Liver anatomy