Excretion

• What is the primary role of the liver in metabolism?

  The liver plays a crucial role in metabolism by facilitating many chemical reactions.
• Why is excretion important for cells?

  Excretion is essential for removing metabolic waste to maintain normal metabolism and homeostasis.
• What waste products are generated during metabolism?

  CO₂ and nitrogenous substances are generated as waste products during metabolism.
• How is CO₂ excreted from the body?

  CO₂ is excreted by cells following respiration and removed from the body by the lungs.
• Where are many metabolic waste products like urea metabolized?

  Many metabolic waste products, like urea, are metabolized in and excreted from the liver cells.
• What is the function of the liver in detoxification?

  • Breaks down toxic substances (alcohol, medications, hormones, excess amino acids)
  • Converts them into less harmful compounds for excretion
• What happens to amino acids in the liver?

  Amino acids are broken down through deamination, producing toxic ammonia and keto acid
• What is produced when ammonia combines with CO₂ in the liver?

  Urea is produced when ammonia combines with CO₂ via the ornithine cycle.
• Where does the ornithine cycle occur in the liver?

  The ornithine cycle occurs partially in the mitochondria of liver cells.
• How is urea excreted from the body?

  Urea is excreted from liver cells, enters the bloodstream, and is filtered out by the kidneys as part of urine.
• What are some substances detoxified by the liver?

  • Alcohol: broken down by ethical dehydrogenase
  • Hydrogen peroxide: split by catalase into oxygen and water
  • Paracetamol: broken down to prevent toxicity
  • Insulin: metabolized to regulate blood glucose concentration
• What are the functions of the liver in regulating blood glucose?

  • Converts excess glucose into glycogen
  • Stores glycogen granules
  • Releases glucose into the bloodstream by breaking down glycogen when levels fall
• What happens to hemoglobin from old red blood cells in the liver?

  Hemoglobin is broken down into bile pigments in hepatocytes by kupffer cells
• How are bile pigments transported after being excreted from liver cells?

  Bile pigments are transported by the bile duct to the gallbladder for storage.
• What are the key large parts of the liver structure?

  1. Hepatic artery: supplies oxygenated blood
  2. Hepatic vein: carries away deoxygenated blood
  3. Hepatic portal vein: brings nutrient-rich blood from intestines
  4. Bile duct: transports bile to the gallbladder
• What is the structure of liver lobules?

  • Composed of numerous lobules with hepatocytes
  • Hepatocytes have large nuclei, prominent Golgi apparatus, and several mitochondria
• What are the key cells and tissues in each liver lobule?

  1. Hepatocytes arranged along sinusoids
  2. Sinusoids mix oxygen-rich blood and nutrient-rich blood
  3. Branch of hepatic vein removes deoxygenated blood
  4. Kupffer cells ingest pathogens
  5. Bile canaliculus links to a branch of the bile duct