Search results
Results from the WOW.Com Content Network
In normal liver, stellate cells are described as being in a quiescent state. Quiescent stellate cells represent 5-8% of the total number of liver cells. [4] Each cell has several long cytoplasmic protrusions that extend from the cell body and wrap around the sinusoids. [5] The lipid droplets in the cell body store vitamin A as retinyl palmitate ...
The capacity to store retinol in the liver means that well-nourished humans can go months on a vitamin A deficient diet without manifesting signs and symptoms of deficiency. Two liver cell types are responsible for storage and release: hepatocytes and hepatic stellate cells (HSCs).
Eighty to ninety percent of the total body reserves of preformed vitamin A are in the liver (with 80–90% of this amount being stored in hepatic stellate cells and the remaining 10–20% being stored in hepatocytes). Fat is another significant storage site, while the lungs and kidneys may also be capable of storage. [21]
The perisinusoidal space also contains hepatic stellate cells (also known as Ito cells or lipocytes), which store vitamin A in characteristic lipid droplets. [2] This space may be obliterated in liver disease, leading to decreased uptake by hepatocytes of nutrients and wastes such as bilirubin.
In the first trimester fetus, the liver is the main site of red blood cell production. By the 32nd week of gestation, the bone marrow has almost completely taken over that task. [56] The liver helps in the purification of blood. The Kupffer cells of liver are phagocytic cells that help in the phagocytosis of dead blood cells and bacteria from ...
Unlike the other twelve vitamins, vitamin D is only conditionally essential - in a preindustrial society people had adequate exposure to sunlight and the vitamin was a hormone, as the primary natural source of vitamin D was the synthesis of cholecalciferol in the lower layers of the skin's epidermis, triggered by a photochemical reaction with ...
Vitamin A in food exists either as preformed retinol – an active form of vitamin A – found in animal liver, dairy and egg products, and some fortified foods, or as provitamin A carotenoids, which are plant pigments digested into vitamin A after consuming carotenoid-rich plant foods, typically in red, orange, or yellow colors. [27]
CYP2R1 is cytochrome P450 2R1, an enzyme which is the principal vitamin D 25-hydroxylase. [5] [6] In humans it is encoded by the CYP2R1 gene located on chromosome 11p15.2. [7]It is expressed in the endoplasmic reticulum in liver, where it performs the first step in the activation of vitamin D by catalyzing the formation of 25-hydroxyvitamin D. [8]