H4 Functions of the liver
Mar 31, 2015
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.
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.
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 vein which carries blood back to the heart
Circulation of blood through liver tissue
hepatic artery carries oxygenated blood to the liverhepatic 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
veinhepatic vein carries blood away from liver to the heart
The roles of the liverThe 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
Role of the liver in regulating levels of nutrients in the blood
Role of the liver in the storage of nutrientsliver 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
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
Role of liver in detoxificationliver 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
Animation: Hemoglobin Breakdown in the Liver
Process of erythrocyte & hemoglobin breakdown in the liver
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 haem groups 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 deaminated into ammonia & hydrocarbon
ammonia is converted to urea while the hydrocarbon (carbohydrate) is respired
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;
Outline the circulation of blood through liver tissue. [3]
Explain the liver damage caused by excessive alcohol consumption. [5]