Liver

• How is carbon dioxide excreted in mammals?

  It is excreted from the lungs as a waste product of cellular respiration
• What are bile pigments and how are they formed?

  Bile pigments are formed from the breakdown of haemoglobin from old red blood cells in the liver
• Where are bile pigments excreted?

  They are excreted in the bile from the liver into the small intestine
• What is the primary nitrogenous waste product in mammals?

  Urea
• How is urea formed in mammals?

  Urea is formed from the breakdown of excess amino acids by the liver
• How do fish and birds differ in their nitrogenous waste products?

  Fish produce ammonia, while birds produce uric acid
• How is urea excreted from the body?

  Urea is excreted by the kidneys in the urine
• Which vessel provides the liver with its rich blood supply?

  the hepatic artery
• What is the role of the hepatic portal vein?

  • The hepatic portal vein carries blood loaded with the products of digestion from the intestines to the liver
  • this is so the products of digestion can be metabolised
• What happens to the blood from the hepatic artery and hepatic portal vein in the liver?

  The blood is mixed in spaces called sinusoids surrounded by hepatocytes
• What are hepatocytes and their characteristics?

  Hepatocytes are liver cells that have large nuclei, prominent Golgi apparatus, and many mitochondria
• What is transamination?

  Transamination is the conversion of one amino acid into another
• Why is transamination important?

  It helps overcome the problems of an unbalanced diet in amino acids
• What is deamination?

  Deamination is the removal of a toxic amino group from a molecule
• What happens to excess ingested protein in the body?

  Excess ingested protein is excreted if not processed by the liver
• How does the liver process amino acids?

  The liver deaminates amino acids, converting them into ammonia and then to urea
• What is the ornithine cycle?

  The ornithine cycle is a set of enzyme-controlled reactions that convert ammonia into urea
• Why is ammonia considered dangerous?

  Because it is very toxic in high concentrations
• What are the functions of the liver?

  • Metabolism of carbohydrates
  • Deamination of excess amino acids
  • Detoxification of harmful substances
  • Production of bile
  • Regulation of blood glucose levels
• What are the differences between the nitrogenous waste products of different organisms?

  • Mammals: Urea
  • Fish: Ammonia
  • Birds and insects: Uric acid
• What does the mixing of blood from the hepatic artery and hepatic portal vein in the sinusoids help with?

  • Increases oxygen of blood of hepatic portal vein
  • Hepatocytes are supplied with more oxygen to release energy for breaking down substances
• True or false? The body is capable of storing proteins and amino acids

  FALSE- the body cannot store excess protein or amino acids
• describe the gross structure of the liver (veins, arteries, lobes)

  •Largest internal organ, reddish-brown, divided into lobes.

  •Hepatic artery and portal vein bring blood to liver, hepatic vein carries blood away.

  •Bile duct system collects bile produced by liver cells.
• describe the microscopic structure of the liver

  •Functional units are lobules, hexagonal structures with central vein.

  •Hepatocytes (liver cells) arranged in plates radiating from central vein.

  •Sinusoids (blood-filled spaces) between hepatocyte plates, lined with Kupffer cells (phagocytes).

  •Portal triad at each corner of lobule: hepatic artery branch, portal vein branch, bile ductule.
• describe the general functions of the liver

  •Metabolism: Carbohydrate, lipid, and protein metabolism, detoxification, bile production.

  •Storage: Glycogen, vitamins, iron.

  •Blood filtration: Kupffer cells remove old RBCs, bacteria, debris.
• what are the similarities and differences between the kidney and the liver? (PPQ)

  Comparison-

  Both:

  •Highly vascularized organs involved in filtration and processing of blood.

  •Microscopic structures (lobules/nephrons) are the functional units.

  •Play crucial roles in homeostasis and waste elimination.

  
  

  Differences:

  •Liver is larger, has a more uniform structure, and performs diverse metabolic functions.

  •Kidney has a more complex structure specialized for filtration and urine formation.

  Liver produces bile, while kidney produces urine
• what are Kupffer cells in the liver?

  • macrophages
  • help to ingest foreign particles and protect against disease
• how does the liver help regulate blood glucose levels?

  • when insulin is released from pancreas, stimulates hepatocytes to convert glucose to glycogen
  • when glucagon is released, stimulates hepatocytes to convert glycogen into glucose
• show how amino acids are converted to ammonia and then to urea

  • AA + oxygen -> keto acid + ammonia (deamination)
  • Ammonia + CO2 -> urea + water (part of the ornithine cycle)

  
• what substances apart from amino acids does the liver detoxify?

  • hydrogen peroxide- to oxygen and water, hepatocytes contain the enzyme catalase
  • conversion of ethanol to ethanal- using alcohol dehydrogenase, and then to ethanoate which may be used to build up fatty acids, or used in respiration
• state the structures you would see in the micrograph of liver tissue

  stained micrograph:

  A) central vein

  B) sinusoids

  C) hepatocytes