Physiology of Liver GB Pancreas Flashcards
What is digestion?
catabolic process that breaks down complex food molecules to mo
What is absortion?
passage of digested end products from the lumen of the GIT through mucosal cells into the blood or lymph
What is the composition of bile?
Main: assist digestion + absorption
- Bile salts*
- Phospholipids (lecithin)*
Other
•Bile pigments (bilirubin)
•Cholesterol, triglycerides
•Electrolyte
What are the functions of bile?
Main: Digestion & absorption
Other: excretion of waste products: bilirubin + cholesterol
How do digestion and absorption in bile work?
Emulsification of large fat particles into small droplets (bile salts have detergent properties)
- This increases SA available for lipases to act upon the fat molecules
- Bile salts & phospholipids interact with the breakdown products of fat digestion – forming micelles
- Micelles “ferry” free fatty acids & monoglycerides to the intestinal mucosa for absorption
What is the composition of the pancreatic juice?
enzymes, water & electrolytes (HCO3-)
What are the pancreatic enzymes?
Proteases: digest proteins
•Amylase: digests starch
•Lipases: digest emulsified fats
•Nucleases: digest nucleic acid
How does the body regulate bile and pancreatic secretion?
Hormonal regulation
CCK & secretin released by duodenal enteroendocrine cells, in response to fatty, acidic or protein-rich chyme
- CCK: pancreatic secretion (enzyme component), GB contraction & relaxation of hepatopancreatic sphincter
- Secretin: pancreatic secretion (H2O & HCO3- component), bile secretion
- Return of bile salts from enterohepatic circulation: bile secretion
How do digestive enzymes work?
Hydrolisis: water is added to molecules for break down.
Are produced by various organs of the GIT
•Act as organic catalysts (accelerate chemical reactions without appearing in final product)
•Each enzyme possesses an active site for a specific substrate
•Function optimally at a specific pH
•Most are synthesised as zymogens (proenzyme
