Accessory organs

• Accessory organs of the digestive system

  • Liver
  • Gallbladder
  • Pancreas

  
• The liver weighs approximately 1.5 kg

  
• The liver has four lobes
• Main functions of the liver

  • Metabolism
  • Storage
  • Detoxification
  • Protein production
  • Bile production
  • Phagocytosis
• Metabolism

  Catabolism: break down of nutrients; Anabolism: build up of new molecules
• The liver is suspended from the diaphragm and attached to the anterior wall of the abdominal cavity by ligaments (peritoneal folds)
• Blood supply to the liver

  75% from portal vein (nutrient rich, oxygen poor)

  25% from hepatic artery (oxygen rich)
• Enterohepatic circulation

  First access from gut (nutrients, toxins, medications)
• Hepatic lobule


  Functional unit of the liver, hexagonal shape with six portal triads and central vein

  
• Components of portal triad

  • Portal venule
  • Hepatic arteriole
  • Bile duct

  
• Hepatocytes help maintain normal blood glucose levels
• Functions of hepatocytes

  • Glycogenesis
  • Glycogenolysis
  • Store vitamins
  • Store minerals
  • Synthesize proteins
  • Synthesize lipoproteins
  • Regulate lipid metabolism
  • Detoxify harmful substances
  • Synthesize bile
• Endothelial cells make the leaky lining of sinusoids (fenestration) -> diffusion of blood to hepatocytes
• Kupffer cells are macrophages specific to the liver (destroy bacteria, remove damaged blood cells
• Stellate cells store vitamin A and control turnover of extracellular matrix
• Components of bile


  • Bile salts
  • Water
  • Bilirubin (yellow substance from breakdown of red blood cells)
• Bile emulsifies fat into smaller pieces which can then be digested by lipase
• Bile secretion process

  1. Secreted in bile canaliculi

  2. Bile ductule

  3. Bile duct (portal triad)

  4. Gallbladder (storage)
• Gallbladder is a muscular membranous sac that stores bile
• Cholelithiasis

  • Formation of gallstones or biliary calculi
  • cholesterol or bilirubin precipitations
• Treatments for cholelithiasis

  • Drugs to dissolve them
  • Ultrasound (lithotripsy)
  • Laser treatment
  • Surgical removal of the gallbladder (cholecystectomy)
• Jaundice is yellowing of the eye’s sclera and skin due to excessive amounts of bilirubin in the blood
• Types of jaundice

  • Hemolytic/pre-hepatic (from destruction of red blood cells)
  • Hepatocellular/hepatic (damaged hepatocytes)
  • Obstructive/post-hepatic (blockage of bile drainage)
• Cirrhosis is scarring of the liver due to long-term liver damage
• Cirrhosis is caused by stellate cells activated by injured hepatocytes
• Cirrhosis is an aberrant wound healing process because of constant injury leading to fibrosis
• Excessive collagen formation in cirrhosis creates portal hypertension by compressing the sinusoids -> fluid moves to peritoneal cavity
• Liver transplant


  Surgery to replace a diseased liver with a healthy liver from another person
• The liver can regenerate lost or injured tissue
• Ex vivo perfusion


  A machine keeps organs warm by continuously pumping blood
• Advantages of ex vivo perfusion

  • Reduction of cold ischemic time -> improved organ quality
  • Extended operating window ->organ survives longer out of body
  • Quality assessment
  • Increase in available organs for transplant
• The pancreas is located in the retroperitoneum
• The pancreas extends across the abdomen from its head to its tail
• Parts of the pancreas

  • Head
  • Neck
  • Body
  • Tail
• Functions of the pancreas

  • Exocrine: enzymes production
  • Endocrine: hormones production
• Endocrine pancreas

  Secretes hormones into the bloodstream (langerhans cells)
• Exocrine pancreas


  Major digestive gland that secretes digestive enzymes (acinar cells)

  
• Exocrine pancreas secretes

  • Bicarbonate
  • Amylase
  • Lipase
  • Nuclease
  • Proteases
• Proteases

  Inactive form, proenzymes or zymogens
• Secretion is stimulated by hormones

  Secretin and cholecystokinin produced in the duodenum in response to entrance of chyme