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H4 Functions of the liver

H4 Functions of the liver. Assessment Statements. H.4.1 Outline the circulation of blood through liver tissue, including the hepatic artery, hepatic portal vein, sinusoids and hepatic vein. H.4.2 Explain the role of the liver in regulating levels of nutrients in the blood.

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H4 Functions of the liver

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  1. H4 Functions of the liver

  2. Assessment Statements • H.4.1 Outline the circulation of blood through liver tissue, including the hepatic artery, hepatic portal vein, sinusoids and hepatic vein. • H.4.2 Explain the role of the liver in regulating levels of nutrients in the blood. • H.4.3 Outline the role of the liver in the storage of nutrients, including carbohydrate, iron, vitamin A and vitamin D. • H.4.4 State that the liver synthesizes plasma proteins and cholesterol. • H.4.5 State that the liver has a role in detoxification. • H.4.6 Describe the process of erythrocyte and hemoglobin breakdown in the liver, including phagocytosis, digestion of globin and bile pigment formation. • H.4.7 Explain the liver damage caused by excessive alcohol consumption.

  3. The circulation of blood through liver tissue • the liver is a large, lobed organ located immediately below the diaphragm, and above and around the stomach • liver is supplied with blood by the hepatic artery & hepatic portal vein • hepatic artery delivers oxygenated blood from the heart • hepatic portal vein brings deoxygenated blood to the liver from the small intestine which also contains nutrients • liver is drained by the hepatic veinwhich carries blood back to the heart

  4. Circulation of blood through liver tissue • hepatic artery carries oxygenated bloodto the liver • hepatic portal vein carries deoxygenated blood to the liver from blood from the gut (small intestine) • blood from hepatic portal vein and hepatic artery mix & flows through sinusoids (i.e. blood-filled channels), past lines of liver cells • from the sinusoid, the blood then flow on to a branch of the hepatic vein • hepatic vein carries blood away from liver to the heart

  5. The roles of the liver • The liver performs more than 500 functions, which includes: • regulation of nutrient levels in the blood; • site of syntheses of plasma proteins & cholesterol; • detoxification of poisons; • breakdown of hemoglobin; • storage of nutrients; • production of bile pigments

  6. Role of the liver in regulating levels of nutrients in the blood

  7. Role of the liver in the storage of nutrients • liver stores excess glucose as glycogen, it releases glucose from glycogen as levels drop • liver breaks down red blood cells (haemoglobin) and stores iron • liver stores fat soluble vitamins such as vitamin A, vitamin D, vitamin E, vitamin K & vitamin B12 (folic acid) • stored nutrients are released from the liver when needed elsewhere in the body

  8. Role of liver in synthesis of plasma proteins &cholesterol • liver is the site of synthesis of all the blood proteins, including globulins, albumin, prothrombin & fibrinogen • most of the cholesterol required by the body on a daily basis is manufactured in the liver, the remainder is taken in as part of the diet • cholesterol synthesized in the liver has a variety of functions including being a component of cell membranes

  9. Role of liver in detoxification • liver detoxifies harmful substances such as: alcohol, drugs & toxins that have entered the blood stream by breaking them into harmless forms for excretion • drugs such as the antibiotics penicillin & erythromycin and sulphonamides are also broken down into harmless wastes which are then excreted • hormones such as thyroid hormone, and steroid hormones such as oestrogen, testosterone, & aldosterone are similarly inactivated, ready for removal from the blood through the kidney

  10. Animation: Hemoglobin Breakdown in the Liver

  11. Process of erythrocyte & hemoglobin breakdown in the liver

  12. Process of erythrocyte &hemoglobin break down in the liver • erythrocytes (red blood cells) have a life span of about 120 days after which they rupture • worn-out red blood cells are destroyed by Kupffer cells through phagocytosis in the reticular endothelial system • hemoglobin is split into haemgroups and globins proteins • globins proteins are hydrolyzed to amino acids • iron is removed from haem & stored in the liver or spleen • haem is converted to bilirubin (bile pigments) • bilirubin (bile pigment) transferred to bile • amino acid are deaminatedinto ammonia & hydrocarbon • ammonia is converted to urea while the hydrocarbon (carbohydrate) is respired

  13. Liver damage caused by excessive alcohol consumption • fatty liver causes cirrhosis (inflammation of the liver) from alcohol abuse • i.e. usually from prolonged & excessive drinking of alcohol • products of alcohol metabolism are toxic to cells as alcohol consumption reduces antioxidant activity • leads to replacement of healthy liver cells with fibrous scar tissue • this blocks blood flow through liver , thus loss of functional liver cells, • blocks normal metabolism of carbohydrates, fats & proteins • may lead to decreased ability to remove toxins (through bile) & production of bile and blood proteins • nutritional deprivation / susceptible to infection/hepatic viruses;

  14. Outline the circulation of blood through liver tissue. [3] • Explain the liver damage caused by excessive alcohol consumption. [5]

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