Excretion

• What is excretion?

  Removal of waste products of metabolism
• What are examples of waste products of metabolism?

  Carbon dioxide, urea, and bile pigments
• Bilirubin breaks down haemoglobin
• What are the two valves that allow blood to enter the liver?

  Hepatic artery and Hepatic portal vein.
• What does the hepatic artery carry?

  Oxygenated from the heart (aorta)
• What does the Hepatic portal vein carry?

  Products of digestion system e.g glucose/amino acids
• What vein carries blood out of the liver and where does it go?

  Hepatic vein rejoins to vena cava
• What is the other vessel that is involved in the liver?

  Bile duct = carries bile salts
• What are lobules?

  Hexagonal column containing hepatocytes that are arranged in irregular and interconnected plates around a central vein
• Blood passes through a large endothelium lined spaces called sinusoids
• Blood in the sinusoids are rich in products of digestion and partially oxygenated
• What lines the sinusoids allowing molecules to diffuse into them?

  Hepatocytes
• What is the bile canneleulli?

  Bile canaliculi are small channels in the liver that transport bile from hepatocytes to bile ducts
• What are kupffer cells?

  Liver macrophages that defend itself from pathogens and they destory worn out RBCs/WBCs/forgein matter
• What do kupffer cells break down?

  Haemoglobin into bilirubin
• What are the functions of the liver?

  • Storage = vitamins, glycogen, iron
  • Control of = blood glucose levels, amino acid levels, lipid levels
  • Breakdown = hormones, RBCs,toxins, alcohol
  • Synthesis = RBC in foetus, bile, plasma proteins
• What role does the liver have in carbohydrate metabolism?

  Hepatocytes convert glucose into glyocgen (vice versa) when blood levels rise/fall
• What role does the liver have in the deamination of excess amino acids?

  Removes the amine group from a molecule and convert it into ammonia -> urea = excreted by kidneys

  The remainder of amino acids are fed into cellular respiration
• What role does the liver have in detoxification?

  Hepatocytes contains enzymes which break down substances into momoners so they aren't toxic.

  E.g = hydrogen peroxide is broken down by enzyme catalase to water and oxygen
• Hepatic artery is a narrow blood vessel why hepatic portal vein is a branched vessel
• hepatocytes produce bile which secretes into canaliculi to be drained into gall bladder
• High concentrations of urea in the blood decrease the water potential of blood so water reabsorption increases by kidneys
• ammonia + CO2 + ornithine = citruline
• production of ammonia to be converted happens in the mitochondria of liver cells
• hepatocytes produce bile to emulsify lipids = increase their SA:V so they can be digested quicker
• sinusoids mixes blood to increase the 02 content for cells to work
• after deamination, the rest of the amino acids become pyruvate and is used in respiration for ATP production