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H.4 Functions of the liver - review
Transcript of H.4 Functions of the liver - review
erythrocytes Detoxification Why do we need to regulate levels of nutrients in the blood? Excess nutrients can be dangerous and cause organ damage. Glucose affects osmotic potential of blood (e.g. high blood sugar leads to blood becoming hypertonic which can damage brain). Excess amino acids cannot be stored and can become toxic. Some vitamins can be toxic in high doses, some are stored in liver for times of shortage. Deamination Urea - excreted Plasma proteins: Fibrinogen
Albumin Cholesterol b) Erythrocytes are engulfed by Kupffer cells Karl Wilhelm von Kupffer
(1829-1902) Tadeusz Browicz
(1847-1928) d) Protein part (globin) hydrolysed to amino acids e) Haem part broken down Amino acids are available for protein synthesis g) Iron is removed and attached to a carrier protein (transferrin) for storage in hepatocytes or taken to bone marrow for incorporation into new erythrocytes f) Remainder of haem part is converted into bile pigments f) Secreted into bile channels between sinusoids as a component of bile Bile production Bile salts bilirubin
(greenish-yellow) 98% water
0.8% bile salts
0.2% bile pigments
0.5% cholesterol About 1 litre per day f) Stored in gall bladder and released into duodenum where it emulsifies fats Hepatocytes absorb and break down harmful molecules including:
alcohol Hepatocytes metabolise alcohol in an enzyme pathway. Fatty acids accumulate in liver cells and reduce blood flow, ultimately killing the cells. This leads to the deposition of fibrous (collagen) or adipose (lipid containing) tissue (fibrosis) and ultimately to cirrhosis - a chronic inflammation of the liver. Whilst it is possible to recover from some of the
early stages of liver disease, cirrhosis can lead to liver failure. a) Erythrocytes wear out after about 120 days How did the ancient Greeks know that the liver could regenerate? Alcohol consumption is a major risk factor associated with liver disease, but the evidence is unclear as to the precise relationship between the amount of alcohol you drink and the incidence of liver disease. For example, an Italian study found that liver disease risk increased after consuming 30g (about 3.8 units) of alcohol per day and that after this risk increased with the amount of alcohol consumed (1). Whereas a Chinese study found that 20g of alcohol (about 2.5 units) per day doubled the risk of liver disease, but thereafter found the risk did not increase with each additional dose. (2) 1 Bellantani S, Saccoccio G, Costa G, et al. Drinking habits as co-factors of risk for alcohol induced liver injury: the Dionysos Study Group. GUT 1997;41:845-50.
2 Shen Z, Li YM, Yu CH, et al. Risk factors for alcohol-related liver injury in the island population of China: a population-based case-control study. World J Gastroenterol 2008;14:2255-61.