Week 35 - The Pancreas and liver

• Liver


  Largest internal organ, weighs 1.5kg
• 2000 litres of blood passes through the liver per day
• Blood flow to the liver

  1. From the tissues via the hepatic artery

  2. From the GI tract via the hepatic portal vein
• Blood flow out of the liver

  Via the hepatic vein
• Gall bladder


  Attached to the liver, stores bile made by the liver
• Roles of the liver

  • Glucose metabolism
  • Fat metabolism
  • Protein production
  • Hormone synthesis and secretion
  • Urea production
  • Toxin neutralisation/removal of old red blood components
  • Storage of glucose, vitamins A, D, E, K and B12
• Liver helps to regulate

  The overall chemical composition of the blood
• Carbohydrate (glucose) metabolism by the liver

  1. Liver glycogen can be broken down to release glucose (glycogenolysis) to meet 4-5 hours of the body's energy needs

  2. In a fed state, the liver takes up glucose from the blood and converts it to glycogen again for storage
• Glucagon


  Hormone that breaks down glycogen to glucose for releasing energy to the body
• Insulin


  Hormone that converts glucose to glycogen for storage in the liver
• Liver lobules


  • Functional units formed by hepatic plates, with a central vein and branches of the hepatic portal vein and artery that open onto sinusoids
• Sources of liver damage

  • Poisoning (paracetamol overdose, mushroom poisoning, alcoholic poisoning/cirrhosis)
  • Infection (bacteria and viruses causing infective hepatitis A, B or C)
  • Gallstones
• Alcoholic cirrhosis


  Mortality has increased 7 fold over the last 30 years, leading to 4000 deaths a year in the UK
• Cirrhosis of the liver

  • Destruction of the liver architecture through scarring
  • Liver becomes fatty, growing to 3X its normal size
  • Eventually, shrinking takes place in liver volume
• Acute liver diseases


  • Hepatitis A (HAV)
  • Hepatitis B (HBV)
  • Hepatitis C (HCV)
• Hepatitis B and Hepatitis C


  The most dangerous Hepatitis Viruses
• Jaundice


  Yellow discolouration of the skin due to increased bilirubin concentration, as the liver can no longer excrete it
• Causes of jaundice


  • Excess lysis/destruction of red blood cells
  • Obstruction of the bile duct (obstructive jaundice) due to inflammatory cells, carcinoma or gallstones
  • NASH (non-alcoholic steato-hepatitis) which can develop from metabolic syndrome
• Pancreas


  • Secretes many digestive enzymes, including pancreatic amylase
  • Secretes endocrine hormones insulin and glucagon (only 2% of the organ does this)
• Metabolism regulation


  Hinges on the ratio of insulin to glucagon hormone levels in the blood
• Insulin secretion


  1. β cells of the islet store insulin in cytoplasmic secretory vesicles

  2. After a meal, the β cells release insulin by exocytosis in response to elevated blood glucose levels

  3. Insulin then directs other cells to take up glucose to be stored as glycogen
• Glucagon release


  In the fasting state, the pancreas releases glucagon to release glucose from the liver and other energy stores
• Diabetes Mellitus


  • Diabetes means "flow through a siphon", Mellitus means "honey"
  • Symptoms: Thirst and glucose laden urine
  • Causes: Autoimmune disease where the beta cells are attacked, leading to Type I diabetes (IDDM)
  • Excess glucose in the urine "holds" the water in the kidney lumen so get huge volumes which can lead to dehydration, low blood pressure and coma if left untreated
• Pancreatitis


  • Inflammatory response to damage of the EXOCRINE pancreas, can be either acute or chronic
  • Anything that limits the normal drainage of the ducts leading out of the pancreas allows the enzymes to access normally protected pancreatic tissue and leads to acute inflammation (pancreatitis) episodes
  • Gallstones, tumour or alcohol abuse can also lead to inflammation of the pancreas
  • Chronic pancreatitis is repeated moderate attacks of acute pancreatitis with progressive loss of tissue which is replaced by scar tissue, most often seen in chronic alcoholics