D.3 Functions of the liver Understanding: The liver removes toxins from the blood and detoxifies them Components of red blood cells are recycled by the liver The breakdown of erythrocytes starts with phagocytosis of red blood cells by Kupffer cells Iron is carried to the bone marrow to produce hemoglobin in new red blood cells Surplus cholesterol is converted to bile salts Endoplasmic reticulum and Golgi apparatus in hepatocytes produce plasma proteins The liver intercepts blood from the gut to regulate nutrient levels Some nutrients in excess can be stored in the liver Applications: Causes and consequences of jaundice Dual blood supply to the liver and differences between sinusoids and capillaries Nature of science: Educating the public on scientific claims: scientific studies have shown that high-density lipoproteins could be considered ’good’ cholesterol

Label the liver Liver Hepatic vein Hepatic artery Hepatic portal vein Gall bladder Right lobe Left lobe Applications: Dual blood supply to the liver and differences between sinusoids and capillaries

Hepatic Portal Vein or Hepatic Artery? Brings blood from the heart Brings blood from the stomach and intestines Oxygen rich Majority of blood in liver uses this path Very little oxygen Branches off from the aorta

Hepatic Artery Hepatic Portal Vein Branches off from the aorta Brings blood from the heart Oxygen rich Hepatic Portal Vein Brings blood from the stomach and intestines Majority of blood in liver uses this path Very little oxygen

Hepatic portal vein divides into sinusoids Applications: Dual blood supply to the liver and differences between sinusoids and capillaries

Wider than capillaries and walls not continuously lined with cells Sinusoids Wider than capillaries and walls not continuously lined with cells Applications: Dual blood supply to the liver and differences between sinusoids and capillaries

Sinusoids The blood comes into contact with the hepatocytes (liver cells) Hepatic artery branches into arterioles and these join the sinusoids Applications: Dual blood supply to the liver and differences between sinusoids and capillaries

Sinusoids Sinusoids then merge with venules that lead to the hepatic vein Carries blood from the liver to the vena cava Applications: Dual blood supply to the liver and differences between sinusoids and capillaries

Role of the liver

Role of the liver Regulate nutrients in the blood Absorbs and breaks down toxic substances Protein synthesis Storage Break down of red blood cells

Liver processes nitrogenous waste Regulates Nutrients Regulates nutrients in the blood Glucose stored as glycogen Excess amino acids and proteins broken down and used as energy Liver processes nitrogenous waste Understanding: The liver removes toxins from the blood and detoxifies them

Regulates Nutrients Manages lipids circulating in the blood Lipids broken down and released as other forms Useful in the body Understanding: The liver removes toxins from the blood and detoxifies them

Toxic Substances Absorbs toxic substances from the blood Converts them into non-toxic or less toxic substances Ammonia  Urea Understanding: The liver removes toxins from the blood and detoxifies them

Protein Synthesis Hepatocytes produce proteins in blood plasma Active protein synthesis in hepatocytes Extensive networks of endoplasmic reticula and Golgi body Approx 13 million ribosomes attached to the ER of a typical liver cell Understanding: Endoplasmic reticulum and Golgi apparatus in hepatocytes produce plasma proteins

Storage High blood glucose ________ released _________ stored as____________ Low blood glucose _________ released __________ broken down to__________ Understanding: Some nutrients in excess can be stored in the liver

Storage High blood glucose Insulin released Glucose stored as glycogen Low blood glucose _________ released __________ broken down to__________ Understanding: Some nutrients in excess can be stored in the liver

Storage High blood glucose Insulin released Glucose stored as glycogen Low blood glucose Glucagon released Glycogen broken down to glucose Understanding: Some nutrients in excess can be stored in the liver

More Storage Iron, retinol (vit A) and calciferol (vit D) Stored in liver when in excess Released when a deficit in the blood Understanding: Some nutrients in excess can be stored in the liver

Erythrocyte break down Lifespan of a red blood cell (erythrocyte) approximately 120 days Plasma membrane of old erythrocytes changes to make them recognizable by macrophages Removed from circulation and broken down in liver Most products are recycled Use of Kupffer cells Understanding: Components of red blood cells are recycled by the liver

Kupffer cells Kupffer cells: macrophages that engulf red blood cells Line the sinusoids in the liver Understanding: The breakdown of erythrocytes starts with phagocytosis of red blood cells by Kupffer cells

Kupffer cells Haemoglobin molecule split into globin chains and a heme group Amino acids from globin chains are recycled Heme broken down into iron and bilirubin Understanding: The breakdown of erythrocytes starts with phagocytosis of red blood cells by Kupffer cells

Erythrocyte breakdown Bilirubin released into the blood. Eventually filtered out by kidneys or excreted. Iron bound to protein transferrin and either taken to the liver for storage May also be taken to the bone marrow to synthesize new blood cells Understanding: The breakdown of erythrocytes starts with phagocytosis of red blood cells by Kupffer cells Iron is carried to the bone marrow to produce hemoglobin in new red blood cells

Iron released into cells to create new hemoglobin Transport of Iron Iron may be taken to bone marrow to be added to heme groups in new red blood cells Developing cells have very high levels of transferrin receptors. Iron released into cells to create new hemoglobin Understanding: Iron is carried to the bone marrow to produce hemoglobin in new red blood cells

Role of the liver Regulate nutrients in the blood Absorbs and breaks down toxic substances Protein synthesis Storage Break down of red blood cells

Regulate nutrients in the blood Erythrocyte Breakdown Role of the liver Regulate nutrients in the blood Toxic Substances Erythrocyte Breakdown Storage Protein Synthesis

Jaundice Build up of bilirubin in blood Normal levels: 1.2mg/dl Jaundice: 2.5mg/dl + What are the symptoms? Why might a newborn be susceptible to jaundice? How can it be treated? Applications: Causes and consequences of jaundice

Jaundice Skin and eyes discolored (yellow) Build up of Bilirubin in the blood Jaundice is not a disease itself but is a symptom of an underlying disease of the liver Applications: Causes and consequences of jaundice

Jaundice Newborns have a high turnover of red blood cells (lots being broken down) Liver still developing and cannot break down bilirubin fast enough May not be able to feed properly – cannot egest the bilirubin quickly Applications: Causes and consequences of jaundice

Jaundice Treatment to remove bilirubin can be done by exposing to UV light Converts bilirubin to products that can be excreted easily Underlying cause still needs to be addressed to stop the jaundice Applications: Causes and consequences of jaundice

Outline two roles of the liver (2) Exam Qs Outline two roles of the liver (2) Describe the process of erythrocyte and hemoglobin breakdown in the liver (4)

Exam Q 1 Outline two roles of the liver (2) storage of nutrients; detoxification of poisons; breakdown of hemoglobin; production of bile pigments; synthesis of plasma proteins; synthesis of cholesterol; regulation of nutrients in the blood;

Exam Q 2 Describe the process of erythrocyte and hemoglobin breakdown in the liver (4) erythrocytes rupture when they reach the end of their life span /after 120 days; absorbed by phagocytosis / Kupffer cells in liver from blood; hemoglobin split into globin and heme groups; iron removed from heme leaving bile pigment / bilirubin; bilirubin released into alimentary canal; digestion of globin to produce amino acids; ;

Cholesterol

Cholesterol Absorbed from food in the intestine Also synthesized by hepatocytes Needed for the synthesis of Vitamin D and steroid hormones Needed as a structural component of membranes Used in production of bile Understanding: Surplus cholesterol is converted to bile salts

High Density of Low Density Lipoproteins. Cholesterol High Density of Low Density Lipoproteins. What are these? Which are good and which are bad? Why? What evidence is there to back this up? Nature of science: Educating the public on scientific claims: scientific studies have shown that high-density lipoproteins could be considered ’good’ cholesterol