topic 10 pt 2

• How much bile do hepatocytes produce daily?

  600-1000 mL
• What is the color of bile?

  Yellow-green
• What are the main components of bile?

  Salts, bilirubin, cholesterol, phospholipids, fat-soluble hormones
• What is the pH range of bile?

  1. 6 - 8.6
• What is the function of bile salts?

  Emulsify fats
• Where are more than 90% of bile salts reabsorbed?

  In the ileum
• What hormone stimulates bile secretion from the liver?

  Secretin
• What does secretin increase in bile?

  Water and bicarbonate ion content
• What are the steps involved in bile secretion and release?

  1. Vagus nerve causes gallbladder contraction.
  2. Secretin stimulates bile secretion from the liver.
  3. CCK causes gallbladder contraction and sphincter relaxation.
  4. Bile salts stimulate additional bile secretion.

  
• What are the metabolic functions of the liver related to carbohydrates?

  • Gluconeogenesis: Converts proteins and triglycerides to glucose.
  • Glycogenesis: Converts excess glucose to glycogen.
  • Glycogenolysis: Converts glycogen back to glucose as needed.
• What are the metabolic functions of the liver related to lipids?

  • Synthesis of cholesterol.
  • Synthesis of lipoproteins.
  • Breakdown of fatty acids to ATP.
• What are the metabolic functions of the liver related to proteins?

  • Deamination of amino acids.
  • Conversion of ammonia to urea.
  • Transamination of amino acids.
  • Synthesis of plasma proteins.
• What is the role of the liver in detoxification?

  It detoxifies drugs and alcohol.
• What waste product does the liver remove from old red blood cells?

  Bilirubin
• Which vitamins are stored in the liver?

  A, D, E, K
• What minerals does the liver store?

  Iron and copper
• What is the function of Kupffer’s cells in the liver?

  Phagocytosis of old blood cells and bacteria
• What is the role of the liver in vitamin D activation?

  It activates vitamin D.
• What are the steps involved in carbohydrate digestion?

  1. Salivary amylase in the oral cavity breaks down carbohydrates.
  2. Pancreatic amylase in the duodenum breaks down polysaccharides.
  3. Brush border enzymes convert disaccharides to monosaccharides.

  
• What are the steps involved in protein digestion?

  1. HCl denatures proteins in the stomach.
  2. Pepsin breaks proteins into polypeptides.
  3. Trypsin and chymotrypsin break down proteins into peptides.
  4. Brush border enzymes further digest peptides into amino acids.
• What are the steps involved in lipid digestion?

  1. Lingual lipase in the oral cavity.
  2. Gastric lipase in the stomach.
  3. Bile emulsifies lipids in the small intestine.
  4. Pancreatic lipase breaks down triglycerides into fatty acids and monoglycerides.

  
• What are the steps involved in nucleic acid digestion?

  1. Nucleases in pancreatic juice hydrolyze nucleic acids.
  2. Brush border enzymes further digest nucleotides.
  3. Nucleotides are absorbed by active transport.
• How are monosaccharides absorbed in the small intestine?

  • Absorbed into epithelial cells via secondary active transport (glucose and galactose).
  • Fructose absorbed by facilitated diffusion.
  • Move into capillaries via facilitated diffusion.

  
• How are amino acids absorbed in the small intestine?

  • Absorbed into epithelial cells via secondary active transport.
  • Move into capillaries via diffusion.

  
• What is the composition of chylomicrons?

  • 90% triglyceride
  • 5% cholesterol
  • 4% phospholipid
  • 1% protein
• What is the process of lipid absorption in the small intestine?

  1. Bile emulsifies lipids.
  2. Lipases convert lipids to monoglycerides.
  3. Lipid components diffuse into mucosal cells.
  4. Triglycerides are re-synthesized and form chylomicrons.
  5. Chylomicrons exit epithelial cells into lacteals by exocytosis.

  
• What is the pathway for lipid absorption into the bloodstream?

  • Gut lumen → mucosa → lacteals → lymphatic vessels → thoracic duct → left subclavian vein → heart → liver
• What is the pathway for absorption of proteins, carbohydrates, and short-chain fatty acids?

  • Gut lumen → mucosa → blood capillaries → hepatic portal vein → liver

  
• Where does most absorption take place in the small intestine?

  • Mostly in the duodenum and jejunum
• How are lipid-soluble vitamins absorbed?

  • Travel in micelles and absorbed by diffusion

  
• How is vitamin B12 absorbed in the small intestine?

  • Combines with intrinsic factor before transport into cells in the terminal ileum
• How are electrolytes absorbed in the small intestine?

  • Sodium, potassium, magnesium, calcium, iron, and phosphate absorbed by active transport.
  • Chloride and nitrate move passively following sodium ions.
  • Calcium absorption requires vitamin D.

  
• How much fluid enters the GI tract each day?

  9 litres
• How much water does the small intestine reabsorb daily?

  8 litres
• What percentage of the last litre of water is reabsorbed by the large intestine?

  90%
• How is water absorbed in the small intestine?

  By osmosis through cell membranes into vascular capillaries