A liver sinusoid is a type of
capillary
A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the inn ...
known as a sinusoidal capillary, discontinuous capillary or sinusoid, that is similar to a
fenestrated capillary, having discontinuous
endothelium
The endothelium (: endothelia) 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 r ...
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. 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 cells (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. K ...
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. They play a part in filtration,
endocytosis
Endocytosis is a cellular process in which Chemical substance, 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 (biology and chem ...
, and in the regulation of blood flow in the sinusoids.
The Kupffer cells can
take up and destroy foreign material such as
bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
.
Hepatocytes 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 the development of fibrous connective tissue in response to an injury. Fibrosis can be a normal connective tissue deposition or excessive tissue deposition caused by a disease.
Repeated injuries, ch ...
.
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 changes 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 multicellula ...
that has made these cells highly specialized phenotypically ''
in vitro
''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...
''.
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
Cardiovascular system anatomy
Liver anatomy