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 tissuethe 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 hearthepatic 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]